Notes – Page 7 – NCERT MCQ

Transportation Definitions, Equations and Examples

September 7, 2021

Transportation

Transportation in Human Beings
In human beings, the transportation of various substances to relevant organs and tissues is done by blood and lymph.

Blood circulatory system: The blood circulatory system comprises heart and blood vessels.
Blood: Blood is a connective tissue having a fluid matrix called plasma and three kinds of cells-Red Blood cells, White Blood cells and Blood platelets.

Functions of Blood

Blood is responsible for the transportation of nutrients, respiratory gases, waste products, hormones, enzymes and ions from one part of the body to the other.
Blood plays a role in temperature regulation and protection of the body from the attack of foreign bodies and disease-causing pathogens.
Blood forms a clot at the site of injury thus preventing further loss of blood.

Component of Blood	Function
Plasma	Plasma is colourless. It contains a lot of water and many proteins. The blood cells (WBC, RBC & Platelets) float in this fluid matrix. Plasma without fibrinogen is called serum.
Red Blood Corpuscles	Also known as Erythrocytes, these contain the red coloured pigment haemoglobin, due or RBCto which the blood looks red. These are produced in the bone marrow.
White Blood Corpuscles or WBC	Also known as Leucocytes, these are lesser in number than RBC. These cells protect the body from infections.
Platelets	These also manufacture antibodies, which are responsible for immunity. These are fragments of cells and do not possess nuclei. They participate in the coagulation of blood.

The Human Heart

The heart is a muscular organ which is as big as our fist. Because both oxygen and carbon dioxide have to be transported by the blood, the heart has different chambers to prevent the oxygen-rich blood from mixing with the blood containing carbon dioxide.
Transportation Definitions, Equations and Examples 1
A schematic sectional view of the human heart

Structure of Heart: The Human Heart consists of four chambers:

Two Upper Chambers: Two upper chambers are called atria or auricles. These are right atrium and left atrium. These receive blood from large veins. Vene cava opens in right auricle (RA) and pulmonary veins open in left auricle (LA).
Two Lower Chambers: Two lower chambers are called ventricles- left ventricle (LV) and right ventricle (RV). These transport blood to lungs and the entire body. These chambers are separated by partitions called septa.

Double circulation:

The working of the heart is described below:

The cardiac muscles of all the four chambers of heart relax.
Deoxygenated Blood from large veins, called vena cava, pour into RA.
Pulmonary veins from lungs pour oxygenated blood into LA.
The atria contract.
RA pours deoxygenated blood into RV and LA pours oxygenated blood into LV.
The ventricles contract.
Oxygenated blood from LV is distributed to all parts of the body through aorta.
Deoxygenated blood flows to the lungs from RV through the pulmonary artery.

Transportation Definitions, Equations and Examples 2

We see that the deoxy noted blood comes to the heart, it is oxygenated in the lungs and comes back to the heart from where it is distributed to all parts of the body. This flow of blood twice through the heart is known as double circulation.

Ventricles have thicker muscular walls: Since ventricles have to pump blood into various organs, they have thicker muscular walls than the atria do. Valves ensure that blood does not flow backwards when the atria or ventricles contract.

Transport and exchange of oxygen and carbon dioxide: The separation of the right side and the left side of the heart is useful to keep oxygenated and deoxygenated blood from mixing as such separation allows a highly efficient supply of oxygen to the body. This is useful in animals that have high energy needs, such as birds and mammals, which constantly use energy to maintain their body temperature.

Animals like amphibians or many reptiles have three-chambered hearts and tolerate some mixing of the oxygenated and de-oxygenated blood streams.

Structure of Heart in Fish: Fishes have only two chambers to their hearts, and the blood is pumped to the gills, is oxygenated there, and passes directly to the rest of the body. Thus, blood goes only once through the heart in the fish during one cycle of passage through the body.
Transportation Definitions, Equations and Examples 3

Blood pressure: The force that blood exerts against the wall of a vessel is called blood pressure. This pressure is much greater in arteries than in veins. The pressure of blood inside the artery during ventricular systole (contraction) is called systolic pressure and pressure in artery during ventricular diastole (relaxation) is called diastolic pressure. The normal systolic pressure is about 120 mm of Hg and diastolic pressure is 80 mm of Hg.

The normal blood pressure values are:

Systolic pressure: 120 mm Hg
Diastolic Pressure: 80 mm Hg
This is usually written as 120/80 mm Hg.
Blood pressure is measured with an instrument called a sphygmomanometer.

Hypertension: High blood pressure is also called hypertension and is caused by the constriction of arterioles, which results in increased resistance to blood flow. It can lead to the rupture of an artery and internal bleeding.

Blood vessels: Blood vessels are of three kinds:

Arteries
Veins
Capillaries

A brief summary of their features is given below:
Transportation Definitions, Equations and Examples 4

Maintenance by platelets: These are cells present in the blood which circulate around the body and help the blood to clot at the points of injury.

Lymphatic system: Lymphatic system is regarded as second circulatory system of the human body and consists of the following:

Lymphatic glands and lymph nodes
Lymph vessels and capillaries
Lymph

Lymph: Lymph or tissue fluid is a yellow coloured circulatory fluid that flows in the lymphatic capillaries, which join to form large lymph vessels. It is formed when some amount of plasma, proteins and blood cells escape into intercellular spaces in the tissues through the pores present in the walls of capillaries.

It is similar to the plasma of blood but colourless and contains less protein. Lymph drains into lymphatic capillaries from the intercellular spaces, which join to form large lymph vessels that finally open into larger veins.

Functions of lymph

It contains lymphocyte cells that fight against infections.
It flows only in one direction-from tissue to the heart.
It is called extracellular fluid ac it lies outside cells and bathes the cells.
It returns proteins and plasma from circulation to fluids.
It carries digested fat.
It drains excess fluid from the extracellular space back into the blood.

Differences between blood and lymph:

Blood	Lymph
1. It is a fluid connective	1. It is an extracellular fluid tissue
2. It consists of plasma and blood Cells	2. It consists of matrix and lymphocytes
3. It is red in colour	3. It is colourless
4. It flows in both directions, i.e., from tissues to heart and back	4. It flows only in one direction, i.e., from tissue to heart

Electrocardiograph: It is an instrument which can record the electrical changes during a heartbeat. The muscle fibres of the heart generate electric currents due to which the heart beats rhythmically. The graphic recording is called ECG or Electrocardiogram.

Pacemaker: It is a machine that is inserted in a heart patient whose heart does not beat normally. It actually takes the place of the specialized muscle cells that initiate heartbeat in the patient in which they have stopped functioning.

Transportation in Plants

Need for Proper System of Transportation in Plants

The raw materials absorbed by a plant such as nitrogen, phosphorus and other minerals have to be transported to different plant parts as diffusion processes will not be sufficient to provide raw material in leaves and energy in roots. A proper system of transportation is therefore essential in such situations.

Energy needs Differ between Different Body Designs Plants do not move, and plant bodies have a large proportion of dead cells in many tissues. As a result, plants have low energy needs and can use relatively slow transport systems. The distances over which transport systems have to operate, however, can be very large in plants such as very tall trees.

Transport of Water

The xylem moves water and minerals obtained from the soil. Water and minerals are transported from the soil to the various parts of the plant by tracheids and vessels – the two elements of xylem, which are both non-living conducting tissues.

Mechanism of Transport in Xylem: In xylem tissue, vessels and tracheids of the roots, stems and leaves are interconnected to form a continuous system of water-conducting channels reaching all parts of the plant.
At the roots, cells in contact with the soil actively take up ions.
This creates a difference in the concentration of these ions between the root and the soil.
Water, therefore, moves into the root from the soil to eliminate this difference.
Thus, there is thus a steady movement of water into root xylem, creating a column of water that is steadily pushed upwards.

Transpiration

The loss of water in the form of vapour from the aerial parts of the plant is known as transpiration.
The water which is lost through the stomata is replaced by water from the xylem vessels in the leaf Evaporation of water molecules from the cells of a leaf creates a suction that pulls water from the xylem cells of roots.

Importance of transpiration:

1. Transpiration helps in the absorption and upward movement of water and minerals dissolved in it from roots to the leaves.

2. It also helps in temperature regulation. The effect of root pressure in the transport of water is more important at night. During the day when the stomata are open, the transpiration pull becomes the major driving force in the movement of water in the xylem.
Transportation Definitions, Equations and Examples 5

Transport of Food and other Substances

The tronsport of soLubLe products of photosynthesis is catted translocation and it occurs in phLoem. The phloem transports products of photosynthesis from the leaves where they are synthesized to other parts of the plant. Besides the products of photosynthesis. the phloem transports amino acids and other substances.

These substances ore especiotty delivered to the storage organs of roots, fruits and seeds and to growing organs.

The translocation of food and other substances takes place in the sieve tubes with the help of adjacent companion cells both in upward and downward directions.

Mechanism of Translocation: The translocation in phloem is achieved by utiLising energy.

Material Like sucrose is transferred into phloem tissue using energy Prom ATP.
This increases the osmotic pressure of the tissue causing water to move into it. This pressure moves the material in the phloem to tissues which have Less pressure.

This allows the phloem to move material according to the plants needs.
For example, in the spring, sugar stored in root or stern tissue would be transported to the buds which need energy to grow.

Example 1.
What are the differences between the transport of materials in xylem and phloem?
Answer:
The differences between the transport of materials in xylem and phloem are:

Xylem	Phloem
1. Xylem helps in the transportation of water and dissolved minerals from roots to leaves and other plant parts.	1. Phloem helps in the transportation of dissolved products of photosynthesis from Leaves to other ports of the plant.
2. In xylem, the transport of material takes place through vessels and tracheids which are dead tissues.	2. In phloem, transport of material takes place through sieve tubes with the help of companion cells, which are living cells.
3. In the xylem, upward movement of water and dissolved minerals is mainly achieved due to Osmotic pressure at roots along with transpiration in which suction is created by evaporation of water from the surface of the Leaf.	3. In translocation material is transferred into phloem tissue using energy from ATP. This increases the as osmotic pressure that moves the material in the phloem to the tissues which have Less pressure.
4. Movement of water is achieved by simple physical forces. There is no requirement of energy in the form of ATP	4. The translocation in phloem is an active process and requires energy in the form of ATP

Class 10 Science Notes

Respiration Definitions, Equations and Examples

September 7, 2021

Respiration

Respiration is a biochemical process taking place in the mitochondria and involves exchange of gases oxygen and carbon dioxide and oxidation of food in celLs to release energy. Respiration is essential for life because it provides energy for carrying out all the life processes which are necessary to keep the organisms alive.

Mechanism of Respiration

The first step is the break-down of glucose, a six-carbon molecule, into a three-carbon molecuLe called pyruvate. This process takes place in the cytoplasm.
1. The pyruvate may be converted into ethanol and carbon dioxide. This process takes place in yeast during fermentation. Since this process takes place in the absence of air (oxygen), it is called anaerobic respiration.

2. Breakdown of pyruvate using oxygen takes place in the mitochondria. This process breaks up the three-carbon pyruvate molecule to give three molecules of carbon dioxide and water. Since this process takes place in the presence of air (oxygen), it is called aerobic respiration.

3. Why sometimes we get cramps: Sometimes, when there is a lack of oxygen in our muscle cells, the pyruvate is converted into lactic acid which is also a three-carbon molecule. This build-up of lactic acid in our muscles during sudden activity causes cramps.
Respiration Definitions, Equations and Examples 1

4. The energy released during cellular respiration is immediately used to synthesize a molecule called ATP which is the energy currency for most cellular processes. The energy released during the process of respiration is used to make an ATP molecule from ADP and inorganic phosphate.

5. ATP can be used in the cells for the contraction of muscles, protein synthesis, conduction of nervous impulses and many other activities. The aerobic organisms need to ensure that there is sufficient intake of oxygen.

Differences between Aerobic and Anaerobic Respiration

Aerobic Respiration	Anaerobic Respiration
1. It takes place in the presence of oxygen	1. It takes place in absence of oxygen.
2. End products are carbon dioxide and water	2. End products may be lactic acid (in muscles of animals) or alcohol (in some plants).
3. Considerable energy is released	3. Much less energy is released.
4. The pyruvate formed by glycolysis of glucose in cytopLasm, goes through Krebs cycle and forms water and carbon dioxide	4. The pyruvate formed by glycolysis of glucose in the cytoplasm undergoes fermentation and forms ethyl alcohol.
5. Majority of organisms use this mode of respiration	5. Some organisms such as certain bacteria and yeast use this mode of respiration.

Respiration in Plants and in Animals

Respiration in Plants	Respiration in Animals
1. All parts of a plant like a root, stem. Leaf perform respiration individually	1. Respiration takes place by respiratory organs only. such as skin, gills. spiractes or lungs.
2. There is little transport of gases from one part of the plant to another	2. There is complete transport of respiratory gases from one part to another.
3. Rate of respiration is quite slow	3. Rate of respiration is fast.

Exchange of Gases in Plants

Plant Organ	Exchange of Gases
Roots	Oxygen diffuses into root hairs, which are in contact with oxygen in the soil, and passes into other cells of the root. Similarly, carbon dioxide diffuses from root cells into the soil.
Older portions of root	Exchange of gases takes place through tiny openings, called lenticels, on the layer of dead cells as older portions of the root do not have root hairs.
Stem	In woody plants. the bark has lenticeLs through which exchange of gases take place.
Leaves	Leaves have tiny apertures called stomata through which diffusion of oxygen and carbon dioxide takes place.

Respiration in Plants

1. Plants exchange gases through stomata, and the large intercellular spaces ensure that all cells are in contact with air. Carbon dioxide and oxygen ore are exchanged by diffusion here. They can go into cells. or away from them and out into the air. The direction of diffusion depends upon the environmental conditions and the requirements of the plant,

2. At night, when there is no photosynthesis occurring. CO₂ elimination is the major exchange activity going on. During the day, CO₂ generated during respiration is used up for photosynthesis. hence there is no CO2 release. Instead, oxygen release is the major event at this time.

Respiration in Animals

Animals have specific organs for respiration. All respiratory organs have three common features:

A large. fine and delicate surface area to get enough oxygen.
Thin walls for easy diffusion and exchange of respiratory gases.
Rich blood supply for transport of gases.
In order to protect this surface, it is usually placed within the body. so there have to be passages that will take air to this area.
In addition, there is a mechanism for moving the air in and out of this area where the oxygen is absorbed.

Summary of Respiratory Organs of Animals

Animal	Organ or Respiration
Aquatic animals like fish, prawns and mussels	Gills
Land animals Like frogs, Lizard, birds and humans	Lungs
Earthworm	Skin
Insects	Air tubes or trachea

Rate of Breathing in Aquatic Organisms

The animals that Live in water need to use the oxygen dissolved in water. Since the amount of dissolved oxygen is fairly Low compared to the amount of oxygen in the air, the rate of breathing in aquatic organisms is much faster than than seen in terrestrial organisms.

Respiratory System of Human Beings
Example 1.
Case-Based:
Amir was curious to know the haemoglobin content in human beings and a cow or a buffalo. So, he visited the nearby health centre in his locality to find out what is the normal range of haemoglobin content in human beings. He also visited a veterinary clinic in his locality and found the following chart:
Respiration Definitions, Equations and Examples 2
(A) The normal range of haemoglobin Levels for men and women is tabuLated below.
Select the row containing the correct haemoglobin Level

Adult Women	Adult Men
(a) 8to 10g/dL	14 to 18g/dL
(b) 14to 16g/dL	8 to 12g/dL
(c) 12 to 16g/dL	14 to 18g/dL
(d) 8 to 12 g/dL	12 to 16 g/dL

Answer:
(c) Adult Women: 12 to 16 g/dL;
Adult Men: 14 to 18 g/dL
Explanation: The normal range of haemoglobin levels for men and women are different and is about 12 – 16 gm/dL in adult women and 14 – 18 gm/dL in adult men.

(B) Select the correct statement(s) from the statements given below:
(I) The overage haemogLobin Levels are different for males and females.
(II) The haemoglobin Level is expressed as the amount of hemogLobin in grams (gm) per Litre (L) of whole blood
(III) The average haemoglobin Levels for older adults is higher than aduLts.
(IV) The average haemoglobin Levels for children is about 11 – 14 gmfdL
(a) Both (I) and (IV)
(b) Both (I) and (ill)
(c) Both (II) and (IV)
(d) Both (III) and (IV)
Answer:
(a) Both (I) and (IV)
Explanation: The average levels of haemoglobin is different for males and females and also different for newborns and infants as the haemoglobin level depends upon one’s occupation, gender, nutrition and general health of the person. The haemoglobin level is expressed as the amount of haemoglobin in grams (g) per deciliter (dl) of whole blood. Older adults tend to have lesser haemoglobin levels than adults.

(C) What is the normal range of haemoglobin content in an animal like the buffalo or cow?
Answer:
The normal range of haemoglobin content in an animal like the buffalo or cow is 12.0 to 15.0gm/dL in adults and about 14.0 to 17.0 gm/ dL for calves.

(D) Is there any difference in normal range of haemoglobin content in male and female human beings and animals? Give reasons for your answer.
Answer:
Yes, the normal haemoglobin levels are different in male and female human beings and buffaloes. It is usually higher in males than in females. This is due to the different hormones secreted in males and females.

Transportation of oxygen in human and animals takes place due to respiratory pigment haemoglobin which is present in the red blood corpuscles and has a very high affinity for oxygen. Due to the requirement of varied level of oxygen for executing different types of work, the haemoglobin contents in human being are comparatively more than that of animals.

(E) Assertion (A): The average haemoglobin levels in newborns is higher than adults.
Reason (R): Newborns have lower oxygen levels in the womb and need less red blood cells to transport the oxygen.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Answer:
(c) (A) is true, but (R) is false.

Explanation: Newborns have higher oxygen levels in the womb and need more red blood cells to transport the oxygen and therefore the average haemoglobin levels in newborns is higher than in adults.

Organs of Respiratory System in Humans

The organs of respiratory system of human beings are: Nasal cavity, nostrils, pharynx, trachea, bronchi, bronchioles and lungs. The different parts of respiratory system and their functions are:

Nasal cavity: Air enters the nasal cavity through the external nostrils. Here, air is warmed, moistened and dust particles are entrapped in the mucus. The air passing through the nostrils is filtered by fine hairs that line the passage.
Glottis: It is a slit through which the pharynx leads into the trachea.
Epiglottis: It is a small cartilaginous flap of skin that covers the glottis while swallowing food.
Trachea: It is the windpipe that runs down the neck and divides into bronchi. Trachea does not collapse even when there is not much air in it as it is supported by rings of cartilage.
Larynx or voice box: It is an enlarged part of trachea and is covered by pieces of cartilage forming a box.
Lungs: The lungs lie in the thoracic cavity. Within the lungs, the passage divides into smaller and smaller tubes which finally terminate in balloon-like structures which are called alveoli. The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli contain an extensive network of blood vessels.

Respiration Definitions, Equations and Examples 3

Mechanism of Breathing

The mechanism of breathing involves:
1. Inhalation: The process by which oxygen-rich air is taken inside the lungs is called inhalation and involves the following steps:

The diaphragm and muscles attached to ribs contract.
The thorax moves upwards and outwards, thereby increasing the volume inside thoracic cavity.
Air pressure inside thoracic cavity decreases.
Air from outside rushes into lungs through nostrils, trachea and bronchi.

2. Exhalation: The process by which waste carbon dioxide is pushed outside the lungs is called exhalation and involves the following steps:

The muscles of the diaphragm and ribs relax.
The thoracic cavity contracts and comes back to its original size.
This presses the lungs due to which the carbon dioxide is expelled.

Important
During the breathing cycle, when air is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.
Respiration Definitions, Equations and Examples 4

Differences between Breathing and Respiration

Breathing	Respiration
1. It is a simple physical process	1. It is a complex chemical process
2. It is the mechanism of exchange of gases oxidation of food.	2. It includes breathing and oxygen and carbon dioxide
3. The main outcome is exchange of gases by respiratory organs like lungs	3. The main outcome of respiration is release of energy through oxidation of simple food molecules such as glucose.

Exchange of Gases in Tissues

During breathing, oxygen is taken in and carbon dioxide is given out of the body.
These gases are transported from one place to another by blood in dissolved state.
Oxygen is picked up by blood and transported to tissues.
From the tissues, CO₂ is picked up by blood and it is brought back to the respiratory organs to release it outside the body.
This exchange of gases takes place by diffusion due to the difference in concentration of gases between tissues and blood.

Transport of Respiratory Gases in Human Beings

Respiratory pigments take up oxygen from the air in the lungs and carry it to tissues that are deficient in oxygen before releasing it.
In human beings, the respiratory pigment is haemoglobin which has a very high affinity for oxygen. This pigment is present in the red blood corpuscles.
Carbon dioxide is more soluble in water than oxygen is and hence is mostly transported in the dissolved form in our blood.
Emphysema: This is a condition whereby the area for gaseous exchange in lungs gets reduced in smokers due to which the heart has to pump more blood leading to a heart attack.

Example 2.
What would be the consequences of a deficiency of haemoglobin in our bodies?
Answer:
Haemoglobin is a respiratory pigment that has a very high affinity for oxygen. It takes up oxygen from the air in the Lungs and carries it to tissues which are deficient in oxygen before releasing it. In case of deficiency of haemoglobin in our blood, its oxygen carrying capacity will decrease and this in turn would affect the process of respiration adversely. This may lead to breathlessness and the person may exhibit symptoms of anaemia.

Class 10 Science Notes

Nutrition Definitions, Equations and Examples

September 7, 2021

Autotrophic Nutrition

Autotrophic nutrition is defined as a type of nutrition in which organisms synthesize organic materials (food) from the inorganic source by the process of photosynthesis.

Photosynthesis

The overall equation for photosynthesis is:
6CO₂ + 12H₂O → C₆H₂O₆ + H₂O + O₂

Carbohydrates are utilised for providing energy to the plant. The carbohydrates which are not used
immediately are stored in the form of starch, which serves as the internal energy reserve to be used as and when required by the plant.

Example: green plants and autotrophic bacteria. Events occurring during photosynthesis:

Absorption of light energy by chlorophyll.
Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
Reduction of carbon dioxide to carbohydrates.

These steps need not take place one after the other immediately.
For example, desert plants take up carbon dioxide at night and prepare an intermediate which is acted upon by the energy absorbed by the chlorophyll during the day.

Cross-section of a Leaf:

Nutrition Definitions, Equations and Examples 1
Some cells contain green dots which are cell organelles called chloroplasts which contain chlorophyll.

The function of Chlorophyll:

Chlorophyll is a pigment present in cell organelles called plastid, which lies just below the upper epidermis in a tissue called palisade. It is a photoreceptor molecule. There are different types of chlorophyll molecules like chlorophyll a, b, c, d, e and bacteriochlorophyll. Chlorophylls absorb mostly the blue and red regions of spectrum.

Exchange of Gases in Plants

Gaseous exchange takes place in the leaves through stomata which are tiny pores present on the surface of the leaves. The exchange of gases occurs across the surface of stems, roots and leaves as well.

The plant closes these pores when it does not need carbon dioxide for photosynthesis since large amounts of water can also be lost through these stomata.

The opening and closing of the pore is a function of the guard cells. The guard cells swell when water flows into them, causing the stomatal pore to open. Similarly the pore closes if the guard cells shrink.
Nutrition Definitions, Equations and Examples 2

Raw Materials for Photosynthesis

Water used in photosynthesis is taken up from the soil by the roots in terrestrial plants.
Carbon dioxide is obtained by plants through the stomata in leaves. In most broad-leaved plants, the stomata are present only in the lower surface of the leaf but in narrow-leaved plants, they are equally distributed on both sides of the Leaf. The aquatic plants use the carbon dioxide dissolved in water.
Other materials like nitrogen, phosphorus, iron and magnesium are taken up from the soil.

Example 1.
What are the necessary conditions for autotrophic nutrition and what are its byproducts?
Answer:
The necessary conditions for autotrophic nutrition are:

Presence of chlorophyll in the living cell.
Presence of sunlight to carry out photosynthesis.
Sufficient amount of atmospheric CO₂ which is required for the making of carbohydrates during photosynthesis.
The adequate water supply to different parts of plant.
The byproducts of autotrophic nutrition are starch (Carbohydrate), water and oxygen.

Heterotrophic Nutrition

Heterotrophic nutrition is defined as a type of nutrition in which energy is derived from the intake and digestion of the organic substances of plant or animal source. Ex-animals, bacteria and fungi.

Types of Heterotrophic Mode of Nutrition
The heterotrophic mode of nutrition is of three types:
Nutrition Definitions, Equations and Examples 3

Example 2.
What are the differences between autotrophic nutrition and heterotrophic nutrition?
Answer:
The differences between autotrophic nutrition and heterotrophic nutrition are given below:

Autotrophic Nutrition	Heterotrophic Nutrition
1. In this type of nutrition organisms can synthesize their own food.	1. In this type of nutrition organisms cannot prepare their own food.
2. Raw materials required to prepare food are simple materials from the environment such as carbon dioxide and water in presence of sunlight.	2. Energy is derived from the intake and digestion of inorganic complex organic substances prepared by other organisms, maybe, plants or animals.
3. Green plants and certain bacteria like blue-green nutrition.	3. All animals, most bacteria and fungi have algae that have chlorophyll have autotrophic heterotrophic nutrition.
4. Autotrophs are the producers in the food chain.	4. Heterotrophs are the consumers in the food chain.
5. They store the food in the form of starch.	5. They store the food in the form of glycogen.

Nutrition in Amoeba

The mode of nutrition of amoeba ¡s holozoic.
It feeds on microscopic animals and plants.
Phagocytosis: It is the process of obtaining food.
Amoeba engulfs the food by forming pseudopodia. When the food is completely encircled and the tips of encircLing pseudopodia touch each other, the membrane at that point dissolves and the food is encaptured into the cell Like o bag called food vacuole.
Food gets digested inside the food vacuole by digestive enzymes.
Assimilation: The digested food diffuses into the cytoplasm and is utiLized by the cell
Egestion: The undigested food remains in the food vacuole and is thrown out of the body.

Nutrition Definitions, Equations and Examples 4

Nutrition in Paramecium:

In Paramecium, which is also a unicellular organism, the cell has a definite shape and food is taken in at a specific spot. Food is moved to this spot by the movement of cilia which cover the entire surface of the cell.

Example 3.
Case-Based:
Take 1 mL starch solution (1%) in two test tubes (A and B). Add 1 mL saliva to test tube A and leave both test tubes undisturbed for 20-30 minutes. Now add a few drops of dilute iodine solution to the test tubes.
(A) Select the correct observation on adding few drops of iodine solution to both the test tubes A and B:

Test Tube A	Test Tube B
(a) Colour changes to blue-black	(a) Colour changes to blue-black
(b) No change in colour	(b) Colour changes to blue-black
(c) No change in colour	(c) No change in colour
(d) Colour changes to blue-black	(d) No change in colour

Answer:
(b) Test Tube A: No change in colour; Test
Tube B: Colour changes to blue-black;
Explanation: We will observe a colour change in test tube B, showing presence of starch. Where as test tube A will show no colour change as due to addition of saliva, starch is converted into sugar by the enzyme salivary amylase.

(B) Select the incorrect statements from the statements given below:
(I) Starch is present in both the test tubes A and B even 30 minutes after adding saliva to test tube A.
(II) Only test tube B shows colour change on adding iodine solution.
(III) Starch is present only in test tube B
(IV) Starch is present only in test tube A
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (III) and (IV)
Answer:
(c) Both (I) and (IV)
Explanation: Starch is present only in test tube B as the salivary amylase enzyme present in saliva breaks down starch into sugar in about 30 minutes. Whereas, starch is still present in test tube B as it is not broken down into simpler substances.

(C) What conclusion can be made from this activity regarding the action of saliva on starch?
Answer:
It can be concluded that on addition of saliva in starch solution, the starch gets converted into some other product (here maltose sugar).

(D) Where does carbohydrate digestion begin in human beings?
Answer:
In human beings, carbohydrate digestion begins in the mouth as the salivary glands secrete the enzyme salivary amylase which breaks down the complex starch into sugar.

(E) Assertion (A): The starch solution to which saliva has been added does not turn iodine solution blue black after about 30 minutes.
Reason (R): Saliva contains salivary amylase which breaks down starch to sugar.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of the (A).
Explanation: We will observe a colour change in test tube B only, showing presence of starch. Where as test tube A will show no colour change as due to addition of saliva, starch is converted into sugar by the enzyme salivary amylase.

Nutrition in Human Beings

The human digestive system consists of the alimentary canal and its associated glands.
The organs which are responsible for ingestion, digestion, absorption, assimilation and egestion constitute the digestive system.
Nutrition Definitions, Equations and Examples 5
Human alimentary canal

Peristaltic Movements

The rhythmic contraction of the muscles lining the alimentary canal in order to push the food forward in a regulated manner along the digestive tube so that it can be processed properly in each part is known as peristaltic movements and these occur all along the gut.

Digestion in Mouth

When we eat any food, the first step is crushing of this food by our teeth and also mixing it with saliva. The saliva contains an enzyme called salivary amylase that breaks down starch which is a complex molecule to give sugar. The food is also wetted to make its passage through the alimentary canal smooth.

Digestion in Stomach

It lies below the diaphragm on the left side of the abdominal cavity and is J-shaped. The food is stored and partly digested in the stomach.

The gastric glands present in the wall of the stomach release hydrochloric acid, a protein-digesting enzyme called pepsin, and mucus.

Hydrochloric acid creates an acidic medium that facilitates the action of the enzyme pepsin. The acid also kills the harmful bacteria present in the stomach.

The mucus protects the inner lining of the stomach from the action of the acid under normal conditions. The exit of food from the stomach is regulated by a sphincter muscle which releases it in small amounts into the small intestine.

Digestion in Small Intestine

The small intestine is the site of the complete digestion of carbohydrates, proteins and fats. It receives the secretions of the liver and pancreas for this purpose.

Role of the liver:

The bile juice from liver makes the food alkaline for the pancreatic enzymes to act as the food coming from the stomach is acidic.
Bile salts break the large fat globules into smaller globules increasing the efficiency of enzyme action.
Role of pancreas: The pancreas secretes pancreatic juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.

The walls of the small intestine contain glands that secrete intestinal juice. The enzymes present in it finally convert the proteins to amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol.

End Products of Digestion

The end products of digestion of food are amino acids, glucose and fatty acids and glycerol.

Reason for shorter small intestines in carnivores:

The length of the small intestine differs in various animals depending on the food they eat. Herbivores eating grass need a longer small intestine to allow the cellulose to be digested. Meat is easier to digest, hence carnivores like tigers have a shorter small intestine.

Absorption of Food

These are finger-like projections present in the inner lining of the small intestines which increase the surface area for absorption. The villi are richly supplied with blood vessels that take the absorbed food to each and every cell of the body, where it is utilised for obtaining energy, building up new tissues and the repair of old tissues.

Assimilation

It is the process of utilization of food for building up or replacement purposes and for obtaining energy.

Egestion of Food

The unabsorbed food is sent into the Large intestine where more villi absorb water from this material. The rest of the material is removed from the body via the anus. The exit of this waste material is regulated by the anal sphincter.

Glands Associated with Digestive System

Glands	Description
Salivary Glands	There are three pairs of salivary glands that secrete an enzyme called ptyalin or salivary amylase which digests starch.
Liver	It secretes bile which contains bile pigments and bile salts. The bile secreted by the liver cells is normally stored in the gall bladder.
Pancreas	It lies parallel to and beneath the stomach. It is a large gland that secretes digestive enzymes and hormones insulin and glucagons.

Example 4.
How are fats digested in our bodies? Where does this process take place?
Answer:
The digestion of fats takes place in the small intestine. The first step is the emulsification of fats. Fats are present in the intestine in the form of large globules. The fat-digesting enzymes are not able to act upon large globules efficiently. Small intestine receives the secretions of the liver and pancreas for this purpose.

Bile salts present in the bile juice from the liver emulsify the large globules of fats and break them down into smaller globules. The pancreas secretes pancreatic juice which contains lipase enzymes for breaking down emulsified fats. The walls of the small intestine contain glands that secrete intestinal juice. The enzymes present in it finally convert the fats into fatty acids and glycerol.

Class 10 Science Notes

Life Processes Definitions, Equations and Examples

September 7, 2021

Life Processes

Living creatures must keep repairing and maintaining their structures all the time which might break down due to environmental effects. Since all these structures are made up of molecules, they must move molecules around all the time.

The processes which together perform the maintenance functions of living organisms even when they are not doing anything particular job are life processes.

Nutrition

Nutrition is a process of intake and utilization of nutrients by an organism as an energy source or for biosynthesis of body constituents. It is a process to transfer a source of energy from outside the body of the organism, which we call food, to the inside. Different organisms use different kinds of nutritional processes.

Enzymes

The bio-catalysts used by the heterotrophs for the break down of complex substances into simpler ones before they can be used for the upkeep and growth of the body are called enzymes.

Respiration

The process of acquiring oxygen from outside the body, and to use it in the process of break-down of food sources for cellular needs, is called respiration.
It is a biochemical process taking place in the mitochondria and involves exchange of gases oxygen and carbon dioxide and oxidation of food in cells to release energy.

Oxidation-Reduction Reactions

These are some of the most common chemical means to break-down molecules. For this, many organisms use oxygen sourced from outside the body.

Transportation

In multi-cellular organisms, simple diffusion will not meet the oxygen requirements. Since the food and oxygen are now taken up at one place in the body of the organisms, while all parts of the body need them, this creates a need for a transportation system for carrying food and oxygen from one place to another in the body.

Excretion

The biological process of removal of excess or toxic wastes from the body is called excretion. When chemical reactions use the carbon source and the oxygen for energy generation, they create by¬products that are not only useless for the cells of the body, but could even be harmful. These waste by products are therefore needed to be removed from the body and discarded outside by a process called excretion.

Example 1.
Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
Answer:
Single-celled organisms do not have specific organs for taking in food, exchange of gases or removal of wastes because the entire surface of the organism is in contact with the environment. Whereas, in multi-cellular organisms like humans, all the cells may not be in direct contact with the surrounding environment due to which simple diffusion is insufficient to meet the requirements of all the cells.

Example 2.
What criteria do we use to decide whether something is alive?
Answer:
The criteria we should use to decide whether an organism is alive or not is the molecular movements within the organisms, which are needed for repairing and maintaining their structures which keep breaking down over time due to the effects of the environment.

Class 10 Science Notes

The Modern Periodic Table Definitions, Equations and Examples

September 7, 2021

The Modern Periodic Table

In 1913, Henry Moseley showed that the atomic number of an element is a more fundamental property than its atomic mass. Accordingly, Mendeleev’s Periodic Law was modified and the atomic number was adopted as the basis of the Modern Periodic Table. Modern Periodic Law: ‘Properties of elements are a periodic function of their atomic number.

Elements, when arranged in order of increasing atomic number, lead us to the classification known as the Modern Periodic Table. Prediction of properties of elements could be made with more precision when elements were arranged on the basis of increasing atomic numbers.

Note: See the table on the next page.

Features of Modern Periodic Table

The Modern Periodic Table has 18 verticaL columns known as ‘groups’ and 7 horizontal rows known as ‘periods’.
Position of Elements in the Modern Periodic Table

In order to find the position of an element in the modern periodic table, the group number and period number of the element is to be found out from its electronic configuration.

Period

1. The period number of an element is equal to the number of electron shelLs in its atom. If an atom has two occupied shells, it will belong to the second period.

2. The number of elements in a period is fixed by the maximum number of electrons which can be accommodated in the different shells of an atom.

3. The maximum number of electrons that can be accommodated in a shell is given by the formula 2n², where n is the shell number.
The Modern Periodic Table Definitions, Equations and Examples 1

4. Each period marks a new electronic shell getting filled.

5. If two or more elements have the same number of valence sheLLs, then they belong to the same period of the periodic table.

1st period contains 2 elements and is called very short period.
2nd period contains 8 elements and is called short period.
3rd period contains 8 elements and is called short period.
4th period contains 18 elements and is called long period.
5th period contains 18 elements and is also called the long period.
6th period contains 32 elements and is called very long period.
7th period contains rest of the elements and is incomplete.

Groups

1. The group number of an element having upto two valence electrons is equaL to the number of valence electrons.

2. The group number of an element having more than 2 valence electrons is equal to the number of valence electrons + 10.

Elements having 1 valence electron are placed in Group 1.
Elements having 2 valence electrons are placed in Group 2.
Elements having 3 valence electrons are placed in Group 13.
ELements having 4 valence electrons are placed in Group 14.
ELements having 5 valence electrons are placed in Group 15.
Elements having 6 valence electrons are placed in Group 16.
Elements having 7 valence electrons are placed in Group 17.
Elements having 8 valence electrons are placed in Group 18.

3. The elements in a group do not have consecutive atomic numbers.

4. All the elements in a group have similar electronic configurations and show similar properties. ALL elements contain the same number of valence electrons. Groups in the Periodic Table signify an identical outer shell electronic configuration.

5. The number of shells increases as we go down the group.

6. If two or more elements have the same number of valence electrons, then they belong to the same group of the periodic table.
The Modern Periodic Table Definitions, Equations and Examples 2

Example 1.
Case-Based:
A student studied the Modem Periodic Table and tried to find out the names of elements in Group I, their electronic configuration and similarity in their configuration.
If you look at the long form of the Periodic Table, you will find that the elements Li, Be, B, C, N, O, F, and Ne are present in the second period.
(A) Which of the following statements are incorrect?
(I) The first three elements of Group 1 are H, Li and Na.
(II) Except H, all other elements of Group 1 have one valence electron.
(III) The number of shells remains same on going down the group.
(IV) Groups in the Periodic Table signify an identical outershell electronic configuration.
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)
Answer:
(b) Both (II) and (III)

Explanation: Hydrogen has one valence electron, just like other elements of Group 1, As we go down a group, a new shell is added in the atom.

For example, consider the elements Li, Na and K having atomic number 3,11 and 19 respectively. They belong to group 1 of the Modern periodic table as they have one electron in their valence shell.

(B) The number of valence electrons of fluorine and Group number to which it belongs is:
(a) Number of valence electrons = 7, Group Number = 1
(b) Number of valence electrons = 9, Group Number = 7
(c) Number of valence electrons = 1, Group Number = 17
(d) Number of valence electrons = 7, Group Number = 17
Answer:
(d) Number of valence electrons = 7, Group Number = 17

Explanation: The atomic number of fluorine is 9 and its electronic configuration is (2, 7).
As it has two occupied shells, it is placed in second period and as it has seven valence electrons, it is placed in Group 17 of the Modern periodic table.

(C) Why is the element Be placed in the second period and Al in the third period?
Answer:
The atomic number of Be is 4 and that of Al is 13.
The electronic configuration of be is (2, 2) and that of Al is (2, 8, 3).

As Be has two occupied shells and Al has three occupied shells, Be is placed in second period and Al is pLaced in the third period.

(D) What will be the formula of fluoride of an element E belonging to Group 13 of the Modern Periodic Table?
Answer:
Fluorine has a valency of 1 as it is a halogen and has seven valence electrons. An element E belonging to group 13 has 3 valence electrons and therefore a valency of 3. Therefore, the formula of the compound formed will be EF3.

(E) Assertion (A): All elements in a period have similar properties.
Reason (R): All elements in a group have identical outer shell electronic configuration.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Answer:
(d) (A) is false, but (R) is true.

Explanation: Properties of elements are a periodic function of their atomic number as the properties of elements depend upon their electronic configuration. The elements of a period have the same number of occupied shells but different electronic configuration and hence different properties.

However, elements belonging to the same group have identical outer shell electronic configuration and hence they have similar properties.

Example 2.
Case Based:
A student studied the Modem Periodic Table and tried to find out the names of elements in Group I, their electronic configuration and similarity in their configuration.
If you look at the long form of the Periodic Table, you will find that the elements Li, Be, B, C, N, O, F, and Ne are present in the second period.
(A) Which of the following statements are incorrect?
(I) The first three elements of Group 1 are H, Li and Na.
(II) Except H, all other elements of Group 1 have one valence electron.
(III) The number of shells remains same on going down the group.
(IV) Groups in the Periodic Table signify an identical outershell electronic configuration.
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)
Answer:
(b) Both (II) and (III)

Explanation: Hydrogen has one valence
electron, just like other elements of Group 1, As we go down a group, a new shell is added in the atom.

For example, consider the elements Li, Na and K having atomic number 3,11 and 19 respectively. They belong to group 1 of the Modern periodic table as they have one electron in their valence shell.
The Modern Periodic Table Definitions, Equations and Examples 4
As we can see from the above, a new shell is added as we go down a group.

(C) Why is the element Be placed in the second period and Al in the third period?
Answer:
The atomic number of Be is 4 and that ofAl is 13.

The electronic configuration of be is (2, 2) and that of Al is (2, 8, 3).
As Be has two occupied sheLls and Al has three occupied shells, Be is placed in second period and Al is placed in the third period.

However, elements belonging to the same group have identical outer shell electronic configuration and hence they have similar properties.

Example 3.
Which element has:
(A) two shells, both of which are completely filled with electrons?
Answer:
The element having two shells, both of which are completely filled will have an electronic configuration of (2,8). Therefore, the element Neon (Atomic number = 10) has two shells, both of which are completely filled.

(B) the electronic configuration 2, 8, 2?
Answer:
Electronic configuration (2, 8, 2) means that the atomic number of the element is 12, which is that of Magnesium (Mg).

(C) a total of three shells, with four electrons in its valence shell?
Answer:
Element having three shells, with four electrons in its valence shell or M shell will have the electronic configuration 2, 8, 4. Therefore, the atomic number of the element is 14 and the element is silicon which belongs to group 14.

(D) a total of two shells, with three electrons in its valence shell?
Answer:
Element having two shells, with three electrons in its valence shell or L shell will have the electronic configuration 2, 3. Therefore, the atomic number of the element is 5 and the element is boron which belongs to group 13.

(E) twice as many electrons in its second shell as in its first shell?
Answer:
Element having twice as many electrons in its second shell (L shell) as in its first shell (K shell) will have the electronic configuration 2, 4. Therefore, the atomic number of the element is 6 and the element is carbon which belongs to group 14.

Arrangement of elements in the modern periodic table on the basis of the electronic configurations of their atoms Number of valence electrons
The Modern Periodic Table Definitions, Equations and Examples 5

Position of Hydrogen: There is an anomaly when it comes to the position of hydrogen because it can be placed either in group 1 or group 17 in the first period.
Hydrogen has been placed at the top of Group I, above the alkali metals because the electronic configuration of hydrogen is similar to those of alkali metals. Both have 1 valence electron each. Since the size of hydrogen atom is much smaller than that of aLkali metals, many properties of hydrogen are different from those of alkali metals.

Explanation of the Anomalies of Mendeleev’s Classification of Elements

1. Explanation of the position of hydrogen: A unique position has been given to hydrogen. It has been placed at the top left corner in group 1, period 1 because of its unique characteristics.

2. Explanation for the position of isotopes: Since all the isotopes of an element have the same atomic number, they are put at one place in the same group of the periodic table.

3. Explanation for the Position of Cobalt and Nickel: Since the elements are arranged according to their atomic number, and the atomic number of cobalt is 27 while that of nickel is 28, so cobalt with lower atomic number should come first and nickel with higher atomic number should come later.

Comparison of Mendeleev’s Periodic table and Modern periodic table

Mendeleev’s Periodic Table	Modern Periodic Table
1. Mendeleev’s periodic table is based on atomic mass.	1. Modern periodic table is based on atomic number.
2. There were gaps for undiscovered elements.	2. Modern periodic table maintains uniformity.
3. Noble gases were not placed (as they are not discovered at that time)	3. Noble gases in a separate group named as group-18.
4. There are a total of 8 groups and 6 periods	4. There are a total of 18 groups and 7 periods

Example 4.
How could the Modem Periodic Table remove various anomalies of Mendeleev’s Periodic Table? [NCERT]
Answer:
The Modern Periodic Table is based on grouping elements with similar properties on the basis of their atomic numbers, whereas Mendeleev’s periodic table was based on atomic masses. This led to certain anomalies, such as the position of hydrogen, position of isotopes and the fact that atomic masses do not increase in a regular manner on moving from one element to the next.

Hydrogen has been allotted a unique position, i.e., it is placed at the top of alkali metals in the first group based on similarity in electronic configuration with alkali metals.
The anomaly regarding position of isotopes of an element have been resolved as isotopes of an element have the same atomic number and so they have been allotted the same position in the modern periodic table.
The position of Cobalt and nickel is now justified as the atomic number of Cobalt is less than an atomic number of nickeland hence it is placed at 9th group whereas Nickel is placed at the 10th group.
As the elements have been arranged in the order of increasing atomic number, the number of elements Lying between any two elements can easily be predicted.

Trends in the Modern Periodic Table Valency

The valency of an element is its combining capacity with other atoms in order to attain the nearest inert gas configuration. It is related to the number of valence electrons present in the atom of an element.

Variation along a period: On moving from left to right, the valency increases from 1 to 4 and then decreases to 0 from group 15 to 18 as the valency is determined by the number of valence electrons.

Example: Valency of Na (Z = 11) is 1 as its electronic configuration is 2, 8, 1 and it attains its nearest inert gas configuration by losing one electron.

Valency of O (Z = 8) is 2, as its electronic configuration is (2, 6) and it requires two electrons to attain its nearest inert gas configuration.

Variation along a group: All elements in a group have the same valency as elements in the same group have the same number of valence electrons.

Valency of group 1 elements = Number of valence electrons = 1
Valency of group 2 elements = Number of valence electrons = 2
Valency of group 13 elements = Number of vaLence electrons = 3
Valency of group 14 elements = Number of valence electrons = 4
Valency of group 15 elements = 8 – Number of valence electrons = 3
Valency of group 16 elements = 8 – Number of valence electrons = 2
Valency of group 17 elements = 8 – Number of valence electrons = 1
Valency of group 18 eLements = 8 – Number of valence electrons = 0

Example: Elements Li, Na and K belong to group 1 as they all have one valence electron and hence have valency 1.
Li: 2,1
Na: 2,8,1
K: 2, 8, 8,1

Elements F, Cl and Br belong to group 17 as they all have seven valence electrons and hence have valency 1 (8 – 7).
F: 2,7
CL: 2, 8, 7
Br: 2, 8, 8,7

Example 5.
Element X forms a chloride with the formula XCl2, which is a solid with a high melting point. X would most likely be in the same group of the Periodic Table as
(a) Na
(b) Mg
(c) Al
(d) Si
Answer:
(b) Mg

Explanation: As the formula of chloride of element X is XCI2, and valency of Cl is 1, it means that valency of X is 2. Since metals combine with halogens to form metal halides, X is a metaLwith valency 2 and hence occupies group 2 of the periodic table.

Out of the elements given Na belongs to group 1, Mg to group 2, Al to Group 13 and Si to group 14 of the periodic table.
Therefore, correct answer is Mg.

Example 6.
In the Modem Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling calcium?
Answer:
To find the elements having similar physical and chemical properties as calcium, we have to find their electronic configuration.

We observe that the elements Mg and Sr also have two valence electrons just like Ca. Therefore, Calcium will have properties similar to both Mg and Sr,
The Modern Periodic Table Definitions, Equations and Examples 6

Atomic size

The size of an atom refers to the radius of atom and is the distance between the centre of the nucleus and the outermost shell of an isolated atom. It is expressed in picometer.
1 picometer = 10^-12 m

Variation along a period: On moving from left to right in a period, the size of atoms decreases.

Reason: When we move from left to right in a period, the number of electrons and protons increases. Due to the large positive charge on the nucleus, electrons are pulled more strongly towards the nucleus.

Variation along a group: The size of an atom (radius) increases as we go down in a group Reason: When going from top to bottom in a group, a new shell is added to the atoms which increases the distance between the valence electrons and the nucleus. So, the effective nuclear charge experienced by the valence electrons decreases.

Metallic and Non-metallic Character

Metals are the elements that have 1, 2 or 3 electrons in their valence shell and lose electrons easily to form positive ions or cations. They are present on the Left side and centre of the periodic table. They are calLed electropositive elements as they have a tendency of losing electrons.

Non-Metals are the elements that have 4, 5, 6 or 7 electrons in their valence shell and gain electrons to form negative ions or anions. They are present on the right side of the periodic table. They are called electronegative elements as they have a tendency of gaining electrons.

Metalloids: There are some elements known as metalloids that exhibit properties of both metals and non-metals.
In the Modern Periodic Table, a zig-zag line separates metals from non-metals. The borderline elements – boron, silicon, germanium, arsenic, antimony, tellurium and polonium – are intermediate in properties and are called metalloids or semi-metals.

Variation along a period: The metallic character decreases and non-metallic character increases as we move from left to right in a period.

Reason: When we move from Left to right in a period, the electropositive character of elements decreases, but the electronegative character increases. Due to the large positive charge on the nucleus, electrons are pulled more strongly towards the nucleus.

Example:
Consider the elements of 3rd period. The variation of metalLic character is shown below:
The Modern Periodic Table Definitions, Equations and Examples 7

Variation along with a group: The metallic character increases and non-metallic character decreases as we move from top to bottom in a group.
Reason: When we go down a group, the electropositive character of elements increases as the tendency of an atom to tose electrons increases as the effective nuclear charge experienced by the valence electrons decrease. The electronegative character decreases down o group as the tendency to gain electrons decreases.

Example 7.
Case Based:
Let us study how the tendency ro lose electrons Will change in a group and how this tendency will change
in a period.

In the periodic table, study the change in the tendency to gain electrons as we go from left to right across a period and as we go down a group.

(A) Group 1 eLements when, arranged in increasing order of their reactivity is:
(a) Na < Li < K < Rb < Cs
(b) Cs Rb < K < Na < Li
(c) Li < Na < K < Rb <Cs
(d) K < Na < Li < Rb <Cs
Answer:
(c) Li < Na < K < Rb < Cs

Explanation: The reactivity of a metal depends upon its electropositivity, i.e., its ability to form cations by losing electrons. As we move down a group, a new shell is added in the atom and the outermost electrons are farther away from the nucleus due to which the effective nuclear charge experienced by valence electrons decreases. Therefore, an atom can easily lose electrons. Hence metallic character increases down a group. As Li is at the top of Group 1 and Cs is at the bottom of the group, Cs is more reactive than Li and reactivity increases from top to bottom in a group.

(B) The variation of electronegativity values for the first 20 elements is shown below:
The Modern Periodic Table Definitions, Equations and Examples 8
Study the graph above and select the correct statement:
(I) The alkali metals are the most electronegative elements in a period.
(II) The electronegativity increases as we go down a group
(III) The electronegativity increases as we move from left to right along a period.
(IV) In a given period, the halogens are the most electronegative elements.
(a) Both (I) and (III)
(b) Both (I) and (IV)
(c) Both (II) and (IV)
(d) Both (III) and (IV)
Answer:
(d) Both (III) and (IV)

Explanation: As we move from left to right along a period, the eLectro negativity increases as the ability of atoms to gain electrons increases due to decrease in atomic size. This is due to the increase in effective nuclear charge as electrons are added in the same shell in a period. Since halogens are in group 17, they are the most electronegative elements in a period and alkali eLements are the most electro-positive elements in a period. The electronegativity decreases as we move from top to bottom in a group which is due to the decrease in the effective nuclear charge experienced by valence electrons due to increase in atomic size.

(C) What happens to tendency to gain electron down the group and why?
Answer:
The tendency to gain electron decreases down a group because as the atomic size increases, the effective nuclear charge experienced by valence electrons decreases as the outermost electrons are farther away from the nucleus.

(D) Arrange the elements F, Cl, Br and I in increasing order of reactivity.
Answer:
I < Br < Cl <F.
Explanation: The elements F, Cl, Br and I belong to Group 17 of the modern periodic table.
The electronic configuration of F, Cl, Br and I is given below:
The Modern Periodic Table Definitions, Equations and Examples 9
We observe that a new shell is added when we move down the group due to which the effective nuclear charge experienced by the valence electrons decreases and hence reactivity decreases.

(E) Assertion (A): The tendency to lose electrons decreases as we go from left to right in a period.
Reason (R): The effective nuclear charge acting on the valence shell electrons increases across a period.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of the (A).

Example 8.
By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristic? Ga Ge As Se Be
Answer:
The element Be is placed in the 2nd period and 2nd group of the periodic table. Whereas the elements Ga, Ge, As and Se are placed in 4th period, group 13 to 16 respectively.

As the metals are placed on the left side of the periodic table and non-metals on the right side, we can say that Be is the most metallic of these elements.

Example 9.
Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the Periodic Table. Write the electronic configuration of these two elements. Which of these will be more electronegative? Why?
Answer:
The electronic configuration of the elements is given below:
The Modern Periodic Table Definitions, Equations and Examples 10
Electronegativity is the ability to gain electrons. Nitrogen will be more electronegative than phosphorus as nitrogen has smaller atomic size than phosphorus as it has 2 shells whereas phosphorus has three shells. As the number of shells increases, the distance between the nucleus and valence shell increases due to which it becomes more difficult for an atom to gain electrons.

Chemical Reactivity

The chemical reactivity of an element depends upon the electronic configuration of the atom of the alement.
Variation along a period: The chemical reactivity of elements first decreases and then increases when we move from left to right in a period.

Variation along a group: The chemical reactivity of metals increases on going down in a group.
The chemical reactivity of non-metals decreases on going down in a group.

Example 10.
(A) Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?
Answer:
Yes, Li, Na and K belong to group 1 of the modern periodic table as atoms of all these metals have one valence electron in their outermost shell.
Electronic configuration of Li (Atomic Number=3) is 2,1
Electronic configuration of Na (Atomic Number = 11) is 2, 8,1
Electronic configuration of K (Atomic Number = 19) is 2, 8, 8,1

(B) Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?
Answer:
Both He and Ne are inert gases and have a completely filled valence shell which expLains their chemical inertness.
Electronic configuration of He (Atomic Number = 2): 2
Electronic configuration of Ne (Atomic Number = 10): 2, 8

Nature of Oxides

Variation along a period: The basic nature of oxides decreases and the acidic nature increases as we move from left to right as metal oxides are basic in nature and oxides of non-metals are acidic in nature. Variation along a group: There is no change in the nature of oxides as we go down in a group as aLl elements of the same group have similar chemical nature.

Example 11.
Which of the following statements is not a correct statement about the trends when going from left to right across the periods of Periodic Table.
(a) The elements become less metallic in nature.
(b) The number of valence electrons increases.
(c) The atoms lose their electrons more easily.
(d) The oxides become more acidic.
Answer:
(c) The atoms lose their electrons more easily. Explanation: On moving from left to right along a period, the metallic character decreases. This is because when we move from left to right in a period, the tendency to lose electrons decreases as the effective nuclear charge on the valence electrons increases.

However, the number of valence electrons increases and the non-metallic character also increases because of the increase in the electronegativity. Further, oxides of non-metals are acidic whereas metal oxides are basic in nature.

Example 12.
The position of three elements A, B and C in the Periodic Table are shown below:
The Modern Periodic Table Definitions, Equations and Examples 11
(A) State whether A is a metal or non -metal.
Answer:
Since A belongs to group 17 and the number of valence electrons is 7, it has a valency of 1 it will gain one electron to complete its octet. Therefore, A is a non-metal.

(B) State whether C is more reactive or less reactive than A.
Answer:
C is less reactive than A because as we move down in a group, the reactivity of non-metals decreases. This is because, as we move in a group, the atomic size increases as a new shell is added due to which the distance between the nucleus and valence electrons increases, and hence electronegativity decreases.

(C) Will C be larger or smaller in size than B?
Answer:
C is smaller in size than B because B and C both are placed in the same period and the size decreases as one moves from left to right in a period due to an increase in effective nuclear charge.

(D) Which type of ion, cation or anion, will be formed by element A?
Answer:
A will form anion because it is a non-metal and will gain one electron to complete its octet.

Merits of the Modern Periodic Table

It is based on the atomic number of elements which is the most fundamental property of elements.
It helps us understand why elements in a group show similar properties but elements in different groups show different properties.
It explains the reasons for the periodicity in properties of elements.
The modern periodic table tells us why the properties of elements are repeated after 2, 8,18, and 32 elements.
There are no anomalies in the arrangement of elements in the modern periodic table.

Advantages of the Periodic Table:

The periodic table has made the study of chemistry systematic and easy.
It is easier to remember the properties of an element if its position in the periodic table is known.
The type of compounds formed by an element can be predicted by knowing its position in the periodic table.
A periodic table chart is used as a teaching aid in chemistry in schools and colleges.

Class 10 Science Notes

Mendeleev’s Periodic Table Definitions, Equations and Examples

September 7, 2021

Mendeleev’s Periodic Table

The main credit for classifying elements goes to Dmitri Ivanovich Mendeleev, a Russian chemist. He was the most important contributor to the early development of a Periodic Table of elements wherein the elements were arranged on the basis of their fundamental property, the atomic mass, and also on the similarity of chemical properties.

When Mendeleev started his work, 63 elements were known.
He examined the relationship between the atomic masses of the elements and their physical and chemical properties.
Among chemical properties, Mendeleev concentrated on the compounds formed by elements with oxygen and hydrogen.
He selected hydrogen and oxygen as they are very reactive and formed compounds with most elements, me formulae of the hydrides and oxides formed by an element were treated as one of the basic properties of an element for its classification.
He then took 63 cards and on each card he wrote down the properties of one element.
He sorted out the elements with similar properties and pinned the cards together on a wall.
He observed that most of the elements got a place in a Periodic Table and were arranged in the order of their increasing atomic masses.
It was also observed that there occurs a periodic recurrence of elements with similar physical and chemical properties.

Mendeleev Periodic Law: ‘The properties of elements are the periodic function of their atomic masses’.
Mendeleev's Periodic Table Definitions, Equations and Examples 1

Features of Mendeleev’s Periodic Table

Mendeleev’s Periodic Table contains verticaL columns called ‘groups’ and horizontal rows called ‘periods’.
This table contains 8 groups and 6 periods.
The formula for oxides and hydrides are written at the top of the columns of Mendeleev’s periodic table, where the letter ‘R’ is used to represent any of the elements in the group. For example, the hydride of carbon, CH4, is written as RH4, and the oxide CO2, as RO2.

Achievements of Mendeleev’s Periodic Table
1. Mendeleev’s periodic law predicted the existence of some elements that had not been discovered at that time. Mendeleev Left some gaps in his Periodic Table. Mendeleev named them by prefixing a Sanskrit numeral, Eka (one) to the name of preceding element in the same group.

For example: Scandium, gallium and germanium, discovered later, have properties similar to Eka-boron, Eka-aluminium and Eka-silicon, respectively.

The properties of Eka-Aluminium predicted by Mendeleev and those of the element, gallium which was discovered later and replaced Eka aluminum, are listed as follows.
Mendeleev's Periodic Table Definitions, Equations and Examples 3

2. Mendeleev’s periodic table could predict the properties of several elements on the basis of their positions ¡ri the periodic table.

3. It could accommodate nobte gases when these gases were discovered in a new group without disturbing the existing order.

Limitations of Mendeleev’s Classification

Position of Hydrogen
The electronic configuration of hydrogen resembles that of alkaLi metals. Like alkali metals, hydrogen combines with halogens, oxygen, and sulfur to form compounds having similar formulae. On the other hand, just like halogens, hydrogen also exists as diatomic molecules and it combines with metals and non-metals to form covalent compounds.
Thus, a correct position couLd not be assigned to hydrogen in the periodic table.

Position of Isotopes

The position of isotopes could not be explained since the elements are arranged according to their atomic masses and isotopes are atoms of the same element having similar chemical properties but different atomic masses.

Compounds of H	Compounds of Na
HCl	NaCl
H₂O	Na₂S
H₂S	Na₂S

The position of isotopes, which were discovered much later, could not be explained as they were placed in the same group.

Wrong Order of Atomic Masses

There were a few instances where Mendeleev had to place an element with a slightly greater atomic mass before an element with a slightly lower atomic mass. The sequence was inverted so that elements with similar properties could be grouped together.
For example, cobalt (atomic mass 58.9) appeared before nickel (atomic mass 58.7).
The wrong order of atomic masses of some elements could not be explained.

Non-uniform Variation of Atomic Masses

Another problem was that the atomic masses do not increase in a regular manner in going from one element to the next. So it was not possible to predict how many elements could be discovered between two elements especially when we consider the heavier elements.

Class 10 Science Notes

Early Attempts at Classification of Elements Definitions, Equations and Examples

September 7, 2021

Early Attempts at Classification of Elements

The number of elements known to us is around 118. But around the year 1800, only 30 elements were known and their properties were also not known much. With the discovery of more elements, scientists gathered more and more information about the properties of these elements and looked for ways to organize them on the basis of similarities in their properties.

The earliest attempt to classify the elements resulted in grouping the then-known elements as metals and non-metals. Later further classifications were tried out as our knowledge of elements and their properties increased.

Dobereiner’s Triads:

In the year 1817, Johann Wolfgang Dobereiner, a German chemist, identified some groups having three elements each of which he called ‘triads’.

Dobereiner showed that when the three elements in a triad were written in the order of increasing atomic masses, the atomic mass of the middle element was roughly the average of the atomic masses of the other two elements.
Early Attempts at Classification of Elements Definitions, Equations and Examples 1
Example: Consider the triad consisting of lithium (Li), sodium (Na), and potassium (K) with the respective atomic masses 6.9, 23.0, and 39.0. The atomic mass of sodium (23) is the mean of the masses of lithium and potassium.

Achievements of Dobereiner’s Triads:

This was a great step in predicting the atomic mass and properties of middle elements. The triads identified by Dobereiner are placed in the same group even in the Modern Periodic Table.

Example 1.
What were the limitations of Dobereiner’s classification?
Answer:
All the elements discovered at that time could not be grouped into triads as Dobereiner could identify only three triads from amongst the elements known at that time.

Take the example of N, P and As. Atomic mass of P (31.0) is not an arithmetic mean of atomic masses of N (14.0) and As (74.9), which is 44.4.

Newlands’ Law of Octaves

In 1866, John Newlands, an English scientist, arranged the then-known elements in the order of increasing atomic masses. He started with the element having the lowest atomic mass (hydrogen) and ended at thorium which was the 56th element.

He found that every eighth element had properties similar to that of the first. He compared this to the octaves found in music. Therefore, he called it the ‘Law of Octaves’. It is known as ‘Newlands’ Law of Octaves’. In Newlands’ Octaves, the properties of lithium and sodium were found to be the same. Sodium is the eighth element after lithium. Similarly, beryllium and magnesium resemble each other.
Early Attempts at Classification of Elements Definitions, Equations and Examples 2

Limitations of Newland’s Law of Octaves

1. The Law of Octaves was applicable only up to calcium, as after calcium every eighth element did not possess properties similar to that of the first.

2. Newlands assumed that only 56 elements existed in nature and no more elements would be discovered in the future. But, later on, several new elements were discovered, whose properties did not fit into the Law of Octaves.

3. In order to fit elements into his Table, Newlands adjusted two elements in the same sLot, but also put some unlike elements under the same note. Example:

Cobalt and nickel are in the same slot and these are placed in the same column as fluorine, chlorine, and bromine which have very different properties than these elements.
Iron, which resembles cobalt and nickel in properties, has been placed far away from these elements.

4. Newlands’ Law of Octaves worked well with lighter elements only.

Example 2.
Did Dobereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
Answer:
Yes, Dobereiner’s triads also exist in the columns of Newlands’ Octaves. For example, Li, Na and K form Dobereiner’s triads and they also exist in Newland’s octaves under the same note or column.

Class 10 Science Notes

Soaps and Detergents Definitions, Equations and Examples

September 7, 2021

Soaps

The molecules of soap are sodium or potassium salts of long-chain carboxylic acids.

A soap molecule has:

Ionic (hydrophilic) part
Long hydrocarbon chain (hydrophobic) part

Soaps and Detergents Definitions, Equations and Examples 1

Structure of soap molecule

Example 1.
What change will you observe if you test soap with litmus paper (red and blue)?
Answer:
When soap is tested with blue and red litmus paper, it changes the colour of red litmus to blue but has no effect on blue litmus paper as soap is alkaline in nature.

Micelles:

Most dirt is oily in nature and as we know, oil does not dissolve in water.
Soaps are molecules in which the two ends have differing properties, one is hydrophilic, that is, it dissolves in water, while the other end is hydrophobic, that is, it dissolves in hydrocarbons.
When soap is at the surface of water, the hydrophobic ‘tail’ of soap will not be soluble in water and the soap will align along the surface of water with the ionic end in water and the hydrocarbon ‘tail’ protruding out of water.
Inside water, these molecules have a unique orientation that keeps the hydrocarbon portion out of the water.
The soap molecules, thus form structures called micelles (Figure) where one end of the molecules is towards the oil droplet while the ionic-end faces outside.
This forms an emulsion in water. The soap micelle thus helps in dissolving the dirt in water and we can wash our clothes clean (Figure below).

Soaps and Detergents Definitions, Equations and Examples 2

Cleansing Action of Soap

Soap in theforn, of a micelle is able to clean, since the oily dirt wiLt be collected in the centre of the micelle.
The micelles stay in soLution as a colloid and will not come together to precipitate because of on ion repulsion.
Thus, the dirt suspended in the micelles is also easily rinsed away. The soap micelles ore large enough to scatter Light. Hence a soap solution appears cloudy.

Cleansing Action of Soap

Detergents

Detergents are sodium salts of sulphonic acids or ammonium salts with chlorides or bromide ions. Examples of synthetic detergents are: Sodium n-dodecyl benzene sulphonate and Sodium n-dodecyl sulphate.

Example 2.
Case Based:
Two students performed the activities to study the action of soap and detergents in soft and hard water. The first student took about 10 mL of distilled water (or rainwater) and 10 mL of hard water (from a tubewell or hand-pump) in separate test tubes and added a couple of drops of soap solution to both. He then shook the test tubes vigorously for an equal period of time. The second student took two test tubes with about 10 mL of hard water in each and added five drops of soap solution to one and five drops of detergent solution to the other and shook both test tubes for the same period.
(A) The observations recorded by the first student on adding a few drops of soap solution to 10 mL distilled water and hard water in separate test tubes is given below:

Distilled Water	Hard Water
1. Lot of foam observed	1. Lot of foam observed
2. Curdy precipitate observed	2. Lot of foam observed
3. Lot of foam observed	3. Curdy precipitate observed
4. Curdy precipitate observed	4. Curdy precipitate observed

Select the correct observation
Answer:
(c) Distilled water: Lot of foam observed; Hard water: Curdy precipitate observed Explanation: Soap forms lot of foam with distilled water but forms a curdy white precipitate known as scum when mixed with hard water. This is because the soap molecules react with the calcium and magnesium ions present in hard water to form the scum.

(B) The second student recorded the following observations after adding five drops of soap solution and detergent solution to two test tubes containing hard water.
(I) Both the test tube had an equal amount of foam
(II) The test tube in which soap was added had less amount of foam
(III) The test tube in which detergent was added had less amount of foam
(IV) A curdy solid was formed in the test tube in which soap was added
Select the incorrect observations. I and III
(a) Both (I) and (III)
(b) Both (I) and (IV)
(c) Both (II) and (IV)
(d) Both (III) and (IV)
Answer:
(a) Both (I) and (III)
Explanation: Soaps form an insoluble precipitate in hard water Whereas detergents are effective even in hard water as they do not form insoluble precipitates with the calcium and magnesium ions in hard water.

(C) What will be observed while using soap in water containing calcium sulfate?
Answer:
When we use soap in water containing calcium sulfate, soap forms foam with difficulty but forms an insoluble substance called scum as soap molecules react with the calcium salt found in hard water.

(D) How are soaps and detergents different structurally?
Answer:
The molecules of soap are sodium or potassium salts of long-chain carboxylic acids whereas detergents are generally ammonium or sulphonate salts of long-chain carboxylic acids.

(E) Assertion (A): Soaps are not effective in hard water
Reason (R): The charged ends of detergents do not form insoluble precipitates with the calcium and magnesium ions in hard water.
For the following questions, two statements are given one labeled Assertion (A) and the other labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Answer:
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the (A).

Explanation: Soaps are not effective in hard water as soap molecules react with the calcium and magnesium salts present in hard water, such as CaSO₄, MgSO₄, CaCl₂ and MgCl₂, and forms an insoluble substance known as scum.

However, as the structure of detergents is different from that of soap, the charged ends of detergents do not form insoluble precipitates with the calcium and magnesium ions in hard water.

Effectiveness of Soaps and Detergents in Hard Water

Soap is not effective in hard water as soap reacts with the calcium and magnesium salts, which cause the hardness of water, and forms foam with difficulty and an insoluble substance (scum) remains after washing with water.

Detergents are effective in hard water as the charged ends of these compounds do not form insoluble precipitates with the calcium and magnesium ions in hard water. Thus, they remain effective in hard water. Detergents are usually used to make shampoos and products for cleaning clothes.

Differences between Soaps and Detergents
Soaps and Detergents Definitions, Equations and Examples 4

Class 10 Science Notes

Some Important Carbon Compounds Definitions, Equations and Examples

September 7, 2021

Ethanol

Ethanol is an alcohol and is obtained by the fermentation of molasses which are obtained from sugarcane juice. Its molecular formula is C₂H₅OH. Alcohols are carbon compounds containing – OH group attached to a carbon atom. It can also be considered as derived from an alkane by replacing a hydrogen atom with a hydroxyl group (OH).

Physical Properties of Ethanol

Ethanol is a liquid at room temperature.
Ethanol is commonly called alcohol and is the active ingredient of all alcoholic drinks.
It is used in medicines such as tincture iodine, cough syrups, and many tonics because it is a good solvent.
Ethanol is also solubLe in water in all proportions.
Long-term consumption of alcohol leads to many health problems.

Chemical Properties of Ethanol

Some Important Carbon Compounds Definitions, Equations and Examples 1

Effect of Alcohol on Living Beings:

When large quantities of ethanoL are consumed, it tends to slow metabolic processes and to depress the central nervous system.
This results in lack of coordination, mental confusion, drowsiness, lowering of the normal inhibitions, and finally stupor.
The individual may feel relaxed but does not realise that his sense of judgement, sense of timing, and muscular coordination have been seriously impaired.

Effect of Methanol

Intake of methanol in very small quantities can cause death.
Methanol is oxidised to methanal in the liver.
Methanol reacts rapidly with the components of cells. It causes the protoplasm to get coagulated, in much the same way an egg is coagulated by cooking.
Methanol also affects the optic nerve, causing blindness.

Uses of Ethanol

It is one of the most important organic chemicals and is used as a solvent for lacquers, varnishes, perfumes medicines, etc.
It is used for sterilizing wounds as it is a good antiseptic.
It is used as a fuel in internal combustion engines and as a substitute for petrol in motor cars under the name ‘power alcohol’.
It is used for making antifreeze mixtures, which are used in the radiators of motor vehicles in cold countries.

Tests for Alcoholic Group:

Sodium metal test: When a small piece of sodium metal is added to the organic liquid, bubbles of hydrogen gas are produced, indicating the presence of the alcoholic group.
Ester test: When the organic liquid to be tested is warmed with some glacial acetic acid and a few drops of cone. H₂SO₄, a sweet-smelling substance is formed.

Denatured Alcohol

Ethanol is an important industrial chemical and is subjected to very small excise duty. To prevent its misuse for drinking purposes, the alcohol supplied for industrial, purposes is rendered unfit for drinking by mixing it with some poisonous substances, such as methanol, pyridine, copper sulphate etc. It is known as denatured alcohol.
Rectified spirit: Ethanol containing 5 per cent water is known as rectified spirit.

Harmful effects of drinking alcohol:

Alcohol is an intoxicant. The person loses all senses of discrimination under its influence.
If a person drinks alcohol regularly, he/she becomes dependent on it and becomes an addict.
The body loses its control and gradually one loses one’s consciousness if the dose of alcohol is increased.
It may even cause death if consumed in large quantities as it damages the liver.
It worsens the economic condition of a family.
It has a very bad effect on the psychological development of children.

Ethanoic Acid

Ethanoic acid (CH₃COOH) is commonly known as acetic acid. Its dilute solution in water (5-8%) is known as vinegar and is used for preserving food. The melting point of pure ethanoic acid is 290 Kand hence it often freezes during winter in cold climates. This gave rise to its name glacial acetic acid.

Physical Properties of Ethanoic Acid

It is a colourless, pungent-smelling liquid having a boiling point of 391 K.
It is miscible with water in all proportions.

Chemical Properties of Ethanoic Acid

Some Important Carbon Compounds Definitions, Equations and Examples 2

Uses of Ethanoic Acid

It is used for making synthetic vinegar which is used for preserving food.
It is used as a reagent in a laboratory.
It is used for making white lead [2PbCO₃. Pb(OH)₂] which is used as white paint.

Example 1.
How would you distinguish experimentally between alcohol and o carboxylic acid?
Answer:
Alcohol and o carboxylic acid can be distinguished experimentally by reaction with sodium carbonate (Na₂CO₃) or sodium hydrogen carbonate (NaHCO₃) as alcohol does not react with NaHCO₃ whereas carboxylic acid reacts with NaHC03 and gives a salt, water and brisk effervescence of carbon dioxide gas.

Example: CH₃COOH + NaHCO₃ → CH₃COONa + CO₂ + H₂O

Saponification Reaction

Esters are sweet-smelling substances, These are used in making perfumes and as flavouring agents. Esters react in the presence of an acid or a base to give back the alcohol and carboxylic acid. This reaction is known as saponification because it is used in the preparation of soap.

Class 10 Science Notes

Chemical Properties of Carbon Compounds Definitions, Equations and Examples

September 7, 2021

Combustion:

Carbon, in all its allotropic forms, burns in oxygen to give carbon dioxide along with the release of heat and light. Most carbon compounds also release a large amount of heat and light on burning.

C + O₂ → CO₂ + heat and light
CH₄ + 2O₂ → CO₂ + 2H₂O + heat and light
CH₃CH₂OH + O₂ → CO₂ + H₂O + heat and light

Example 1.
Case-Based:
Two students performed the following activities to study the combustion of hydrocarbons.
The first student took, some carbon compounds (naphthalene, camphor, alcohol) one by one on a spatula and burned them with the teacher’s assistance. He observed the nature of the flame and whether smoke is produced. He then placed a metal plate above the flame and noted down his observations.
The second student lighted a bunsen burner and adjusted the air hole at the base to get different types of flames/presence of smoke.
(A) The observations recorded by the first student are given below:
(I) Naphthalene burns with a yellow flame
(II) Camphor burns with a blue flame
(III) Alcohol burns with a blue flame
(IV) No smoke is produced when these substances are burnt Which of the observations are correct?
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (I) and (III)
(d) (I), (II) and (IV)
Answer:
(c) Both (I) and (III)

Explanation: When alcohol, camphor and naphthalene are taken in a spatula and burnet separately, the yellow coloured flame is observed in the case of camphor and naphthalene as they both are unsaturated hydrocarbons. Whereas, alcohol burns with a blue flame as it is a saturated hydrocarbon

(B) The second student recorded his observations which are given as follows:

Air supply (by adjusting air holes at the base of the burner)	Colour of Flame
(a) Sufficient	Sooty and yellow
(b) Insufficient	Clean and yellow
(c) Insufficient	Sooty and blue
(d) Sufficient	Clean and blue

Select the correct observation.
Answer:
(d) Air supply: Sufficient: Colour of flame: Clean and blue

Explanation: When the air supply is sufficient then, the burns with a clean blue flame as it undergoes complete combustions. However, when the air supply is insufficient, the fuel burns with a sooty yellow flame as all the carbon particles do not burn completely. So, the unburnt carbon particles deposit as soot.

(C) Which out of the following hydrocarbons will give a clean flame when burnt: C₄H₁₀ or C₄H₈?
Answer:
The hydrocarbon C₄H₁₀ or butane will give a clean flame when burnt as it is an aLkane, which is a saturated hydrocarbon containing only single covalent bonds between carbon atoms.

(D) Do saturated hydrocarbons always burn with a blue flame?
Answer:
No, saturated hydrocarbons burn with a blue flame in sufficient supply of oxygen and burn with a yellow sooty flame when supply of oxygen is insufficient.

(E) Assertion (A): Burning of camphor results in a sooty deposit on a metal plate kept over the flame.
Reason (R): Saturated hydrocarbons always burn with a sooty flame.
(a) Both (A) and (R) are true and (R) is the correct explanation of the (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the (A).
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Answer:
(c) (A) is true, but (R) is false.

Explanation: When camphor is burned and a metal plate is kept over the flame, it burns with a yellow sooty flame and a sooty deposit is formed on the metal plate. This is because camphor is an unsaturated hydrocarbon and all unsaturated hydrocarbons burn with a sooty flame due to the incomplete combustion of carbon particles.

Saturated hydrocarbons burn with a clean flame insufficient supply of oxygen.

Colour of Flame on Burning Hydrocarbons

Saturated hydrocarbons will generally give a clean blue flame while unsaturated carbon compounds will give a yellow flame with lots of black smoke.

However, Limiting the supply of air results in incomplete combustion of even saturated hydrocarbons giving a sooty flame.

The gas/kerosene stove used at home has inlets for air so that a sufficiently oxygen-rich mixture is burnt to give a clean blue flame.

If the bottoms of cooking vessels are getting blackened, it means that the air holes are blocked and fuel is getting wasted.

Fuels such as coal and petroleum have some amount of nitrogen and sulphur in them. Their combustion results in the formation of oxides of sulphur and nitrogen which are major pollutants in the environment.

Burning substances and flames: A flame is only produced when gaseous substances burn. When wood or charcoal is ignited, the volatile substances present vapourise and burn with a flame in the beginning.

A luminous flame is seen when the atoms of the gaseous substance are heated and start to glow. The colour produced by each element is a characteristic property of that element.

Formation of Coal and Petroleum

Coal and petroleum have been formed from biomass which has been subjected to various biological and geological processes. Coal is the remains oftrees, ferns, and other plants that lived milLions of years ago. These were crushed into the earth, perhaps by earthquakes or volcanic eruptions. They were pressed down by layers of earth and rock. They slowly decayed into coal.

Oil and gas are the remains of millions of tiny plants and animals that lived in the sea. When they died, their bodies sank to the sea bed and were covered by silt. Bacteria attacked the dead remains, turning them into oil and gas under the high pressures they were being subjected to.

Oxidation

Oxidation is the reaction in which oxygen is added and hydrogen is removed from alcohol. When alcohol is heated with an oxidizing agent such as alkaline potassium permanganate or acidified potassium dichromate, they undergo oxidation and form a carboxylic acid.

AlkaLine potassium permanganate or acidified potassium dichromate are known as oxidising agents as they oxidise alcohols to acids, that is, add oxygen to the starting material

Addition Reaction

The reaction in which an atom or a group of atoms is added to a molecule is known as an addition reaction. Unsaturated hydrocarbons add hydrogen in the presence of catalysts such as palladium or nickel to give saturated hydrocarbons. This reaction is commonly used in the hydrogenation of vegetable oils using a nickel catalyst. Vegetable oils generally have long unsaturated carbon Chains while animal fats have saturated carbon chains.
Chemical Properties of Carbon Compounds Definitions, Equations and Examples 2

Hydrogenation of Vegetable Oils

Oils (such as vegetable, olive, sunflower) are liquids at room temperature. In the food industry, hydrogen is added to oils (in a process called hydrogenation) to make them more solid, or ‘spreadable’. The hydrogenation of oils helps to prolong the sheLf-life of the food and maintain flavour stability.

Since the process of hydrogenation adds hydrogen atoms to oil, it will reduce the number of unsaturated fatty acids and increase the number of saturated fatty acids in the oil.

Animal fats generally contain saturated fatty acids which are said to be harmfuLfor health. Oils containing unsaturated fatty acids should be chosen for cooking.

Example 2.
Which of the following hydrocarbons undergo additional reactions:
C₂H₆, C₃H₈I C₃H₆I C₂H₂ and CH₄.
Answer:
Unsaturated hydrocarbons (alkenes and alkynes) undergo additional reactions as they have double and triple covalent bonds which are the site of chemical reactivity. The general formula of alkenes is C_nH_2n and of alkynes is C_nH_2n-2.

Out of the given hydrocarbons, C₂H₆, C₃H₈ and CH₄ are alkanes as they have the general formula C_nH_2n+2. Hence they will not undergo addition reaction.

C₃H₆ is an alkene (ethene) and will undergo additional reaction.
C₂H₂ is an alkyne (ethyne) and will also undergo additional reaction.

Example 3.
Give a test that can be used to differentiate chemically between butter and cooking oil.
Answer:
Butter contains saturated compounds and cooking oil contains unsaturated compounds. As unsaturated hydrocarbons undergo addition reaction whereas saturated hydrocarbons do not undergo addition reaction, we will use bromine water test to differentiate chemically between butter and cooking oil.

Bromine water (reddish-brown in colour) is decolourized by unsaturated hydrocarbons as they will undergo addition reaction with bromine.
CH₂ = CH₂ + Br₂ → CH₂Br—CH₂Br

Whereas, the brown colour of bromine will be retained on reacting with a saturated hydrocarbon. So, when a small amount of butter and cooking oil are taken and treated with bromine water, cooking oil wilL decolourize the bromine water whereas butter will not have any effect on it.

Substitution Reaction

The reaction in which an atom replaces another atom or a group of atoms from a molecule is called a substitution reaction.

Saturated hydrocarbons are fairly unreactive and are inert in the presence of most reagents. In the presence of sunlight, chlorine is added to hydrocarbons in a very fast reaction. Chlorine can replace the hydrogen atoms one by one. It is called a substitution reaction because one type of atom or a group of atoms takes the place of another. A number of products are usually formed with the higher homologues of alkanes.
CH₄ + Cl₂ → CH₃Cl + HCl (In the presence of sunlight)

Class 10 Science Notes

Homologous Series Definitions, Equations and Examples

September 7, 2021

Homologous Series

A homologous series is a group of organic compounds having similar structures and similar chemical properties in which the successive compounds differ by CH₂ group.

Characteristics of Homologous Series

All the members of a homologous series can be represented by the same general formula.
Any two adjacent homologues differ by -CH₂ or 1 carbon atom and 2 hydrogen atoms in their molecular formula.
The difference in the molecular masses of any two adjacent homologues is 14 u.
All the compounds belonging to the same homologous series have similar chemicaL properties since these are determined solely by the functional group.
The members of a homologous series show a gradual change in their physical properties with an increase in molecular mass. This is because the melting and boiling points increase with increasing molecular mass.

Nomenclature of Carbon Compounds

The names of compounds in a homologous series are based on the name of the basic carbon chain modified by a “prefix” “phrase before” or “suffix” “phrase after” indicating the nature of the functional group.

Naming a carbon compound can be done by the following method:
1. Identify the number of carbon atoms in the compound. A compound having three carbon atoms would have the name propane.

2. In case a functional group is present, it is indicated in the name of the compound with either a prefix or a suffix

3. If the name of the functional group is to be given as a suffix, the name of the carbon chain is modified by deleting the final ‘e’ and adding the appropriate suffix. For example, a three-carbon chain with a ketone group would be named in the following manner – Propane – ‘e’ = propane + ‘one’ = propanone.

4. If the carbon chain is unsaturated, then the final ‘ane’ in the name of the carbon chain is substituted by ‘ene’ or ‘yne’. For example, a three-carbon chain with a double bond would be called propene and if it has a triple bond, it would be called propyne.
Homologous Series Definitions, Equations and Examples 1

Example 1.
How would you name the following compounds?
Homologous Series Definitions, Equations and Examples 3
Answer:
(A) Bromoethane
(B) Methanal
(C) 1-hexyne (as the triple bond is between the first and second carbon atom when numbered from right)

Category: Notes

Transportation

Functions of Blood

The Human Heart

Double circulation:

Functions of lymph

Transportation in Plants

Transport of Water

Transpiration

Importance of transpiration:

Transport of Food and other Substances

Respiration

Mechanism of Respiration

Respiration in Plants

Respiration in Animals

Rate of Breathing in Aquatic Organisms

Organs of Respiratory System in Humans

Mechanism of Breathing

Exchange of Gases in Tissues

Transport of Respiratory Gases in Human Beings

Autotrophic Nutrition

Photosynthesis

Cross-section of a Leaf:

The function of Chlorophyll:

Exchange of Gases in Plants

Raw Materials for Photosynthesis

Heterotrophic Nutrition

Nutrition in Amoeba

Nutrition in Paramecium:

Nutrition in Human Beings

Peristaltic Movements

Digestion in Mouth

Digestion in Stomach

Digestion in Small Intestine

Role of the liver:

End Products of Digestion

Reason for shorter small intestines in carnivores:

Absorption of Food

Assimilation

Egestion of Food

Life Processes

Nutrition

Enzymes

Respiration

Oxidation-Reduction Reactions

Transportation

Excretion

The Modern Periodic Table

Features of Modern Periodic Table

Period

Groups

Explanation of the Anomalies of Mendeleev’s Classification of Elements

Trends in the Modern Periodic Table Valency

Atomic size

Metallic and Non-metallic Character

Chemical Reactivity

Nature of Oxides

Merits of the Modern Periodic Table

Advantages of the Periodic Table:

Mendeleev’s Periodic Table

Features of Mendeleev’s Periodic Table

Limitations of Mendeleev’s Classification

Position of Isotopes

Wrong Order of Atomic Masses

Non-uniform Variation of Atomic Masses

Early Attempts at Classification of Elements

Dobereiner’s Triads:

Achievements of Dobereiner’s Triads:

Newlands’ Law of Octaves

Limitations of Newland’s Law of Octaves

Soaps

Micelles:

Cleansing Action of Soap

Detergents

Effectiveness of Soaps and Detergents in Hard Water

Ethanol

Physical Properties of Ethanol

Chemical Properties of Ethanol

Effect of Alcohol on Living Beings:

Effect of Methanol