NOTES Class 10 Science

 

                  DR OMAR CLASSES KAMPUR

Access Answers to NCERT Class 10 Science Chapter 1 – Chemical Reactions and Equations

In-text questions set 1 Page number – 6

1. Why should a magnesium ribbon be cleaned before burning in air?

Solution:

Magnesium ribbon should be cleaned before burning in air because Magnesium metal reacts with the atmospheric oxygen and forms Magnesium Oxide (MgO) layer which is a very stable compound. In order to prevent further reactions with Oxygen, it is therefore necessary to clean the ribbon by to remove the layer of MgO.

2. Write a balanced equation for the following chemical reactions.

i) Hydrogen + Chloride —-> Hydrogen chloride

ii) Barium chloride + Aluminium sulphate —-> Barium sulphate + Aluminium chloride

iii) Sodium + Water —-> Sodium hydroxide + Hydrogen

Solution:

i) H2 + Cl2 → 2HCl

ii) 3BaCl2 + Al2(SO4)3 →3BaSO4 + 2AlCl3 

iii) 2Na + 2H2O → 2NaOH + H2

3. Write a balanced chemical equation with state symbols for the following reactions

i) Solutions of Barium chloride and Sodium sulphate in water react to give insoluble Barium sulphate and solution of Sodium chloride.

ii) Sodium hydroxide solution in water reacts with hydrochloric acid solution to produce Sodium chloride solution and water.

Solution:

i) BaCl2 + Na2SO4 → BaSO4 + 2NaCl

ii) NaOH + HCl → NaCl + H2O

In-text questions set 2 Page number – 10

1. A solution of a substance ‘X’ is used for whitewashing.

(i) Name the substance ‘X’ and write its formula.

(ii) Write the reaction of the substance ‘X’ named in (i) above with water.

Solution:

i) The substance ‘X’ which is used in whitewashing is quick lime or Calcium Oxide and its formula is CaO.

ii) CaO + H2O → Ca(OH)2

2. Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas

Solution:

In activity 1.7, gas collected in one of the test tubes is double of the amount collected in the other because water gets hydrolysed to release H2 and O2 gas. Here, after electrolysis two molecules of Hydrogen and one molecule of oxygen gas is released, hence the amount of Hydrogen collected would be double than that of oxygen.

In-text questions set 3 Page number – 13

1. Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

Solution:

When an iron nail dipped in the copper sulphate solution, iron displaces copper from the copper sulphate because iron is more reactive than copper. Therefore the colour of the copper sulphate solution changes. The reaction is:

Fe + CuSO4 → FeSO4 + Cu

2. Give an example of a double displacement reaction other than the one given in Activity 1.10.

 Solution:

Reaction Between silver nitrate (AgNO3) and Sodium chloride (NaCl) is an example of double displacement reaction. During the reaction negative and positive ions trade positions as a result in the formation of white silver chloride precipitate. The chemical reaction is given below.

Ag+ + NO3– + Na+ + Cl– → AgCl + Na+ + NO3–

3. Identify the substances that are oxidized and that are reduced in the following equation.

i) 4Na(s) + O2(g) → 2Na2O(s)

ii) CuO(s) + H2(g) → Cu(s) + H2O(l)

Solution:

The Sodium (Na) in the first equation is getting oxidized with the addition of Oxygen (O2) and the Copper (Cu) in the second equation is reduced due to the addition of Hydrogen (H2)

Exercise Questions Page number – 14-16

1. Which of the statements about the reaction below are incorrect?

2PbO(s) + C(s) → 2Pb(s) + CO2(g)

(a) Lead is getting reduced

(b) Carbon Dioxide is getting oxidised

(c) Carbon is getting oxidised

(d) Lead oxide is getting reduced

       (i) (a) and (b)

       (ii) (a) and (c)

       (iii) (a), (b) and (c)

       (iv) all

Solution:

(i) (a) and (b)

Explanation: (a) because Oxygen is being removed and (b) because the removed oxygen from Lead is added to the elemental Carbon.

2.  Fe2O3 + 2Al → Al2O3 + 2Fe

The above reaction is an example of a

1. Combination reaction.
2. Double displacement reaction.
3. Decomposition reaction.
4. Displacement reaction.

Solution:

Answer is 4. Displacement reaction.

Explanation: The Oxygen from the Ferrous oxide is getting displaced to the Aluminium metal to form Aluminium Oxide. In this reaction Aluminum is more reactive metal than Fe. Therefore Al will displace Fe from its oxide. This type of chemical reactions in which one of the elements displace another is called displacement reaction. Here less reactive metal is displaced by more reactive metal. Since one-time displacement is occurring, therefore, it is called a single displacement reaction.

3. What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer.

1. Hydrogen gas and Iron chloride are produced.
2. Chlorine gas and Iron hydroxide are produced.
3. No reaction takes place.
4. Iron salt and water are produced.

Solution:

1. Hydrogen gas and Iron chloride are produced.

Explanation: The Chlorine from Hydrogen chloride is displaced by the Iron fillings to undergo the following reaction.

2HCl + Fe → FeCl2 + H2

4. What is a balanced chemical equation? Why should a chemical equation be balanced?

Solution:

A balanced equation is the one in which number of different atoms on both the reactant and product sides are equal. Balancing chemical equation is necessary for the reaction should obey The Law of Conservation of mass. Balancing the chemical equation has no defined method and is purely a trial and error attempt.

c)  Unbalanced:

BaCl2 + Al2(SO4)3 → AlCl3 + BaSO4

Balanced: 3BaCl2 + Al2(SO4)3 → 2AlCl3 + 3BaSO4

(d) Unbalanced: K + H2O → KOH + H2

Balanced:  2K + 2H2O → 2KOH + H2

6. Balance the following chemical equations.

(a) HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O

(b) NaOH + H2SO4 → Na2SO4 + H2O

(c) NaCl + AgNO3 → AgCl + NaNO3

(d) BaCl2 + H2SO4 → BaSO4 + HCl

Solution:

(a) 2HNO3 + Ca(OH)2 → Ca(NO3)2 + 2H2O

(b) 2NaOH + H2SO4 → Na2SO4 + 2H2O

(c) NaCl + AgNO3 → AgCl + NaNO3

(d) BaCl2 + H2SO4 → BaSO4 + 2HCl

7. Write the balanced chemical equation for the following reactions.

Calcium hydroxide + Carbon dioxide —-> Calcium carbonate + Water

Zinc + Silver nitrate —-> Zinc nitrate + Silver

Aluminium + Copper chloride —-> Aluminium chloride + Copper

Barium chloride + Potassium sulphate —-> Barium sulphate + Potassium chloride

Solution:

2Ca(OH)2 + 2CO2 → 2CaCO3 + 2H2O

Zn + 2AgNO3 → Zn(NO3)2 + 2Ag

2Al + 3CuCl2 → 2AlCl3 + 3Cu

BaCl2 + K2SO4 → BaSO4 + 2KCl

8. Write a balanced chemical equation for the following and identify the type of reaction of each case

KBr + BaI2 → KI + BaBr2

ZnCO3 → ZnO + CO2

H2 + Cl → HCl

Mg + HCl → MgCl2 + H2

Solution:

2KBr + BaI2 → 2KI + BaBr2 (Double Displacement Reaction)

ZnCO3 → ZnO + CO2 (Decomposition Reaction)

H2 + Cl → 2HCl (Combination Reaction)

Mg + 2HCl → MgCl2 + H2 (Displacement Reaction)

9. What is meant by exothermic and endothermic reactions? Give examples.

Solution:

An endothermic reaction occurs when energy is absorbed from the surroundings in the form of heat.(Example: Photosynthesis, melting of ice, evaporation). Conversely, an exothermic reaction is one in which energy is released from the system into the surroundings. (Example: Explosions, concrete setting, nuclear fission and fusion).

10. Why is respiration considered to be an exothermic reaction?

Solution:

For the survival of life, we require energy. We obtain this energy from the food we eat. The food molecules, through the process of digestion, is broken down into a simpler molecule like glucose. These substances come in contact with the Oxygen present in our body cells to form Carbon dioxide and water along with a certain amount of energy (Respiration process). Since the energy is in the form of heat (that maintains our body temperature) the respiration is considered to be an exothermic reaction. The reaction taking place is:

C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy

11. Why are decomposition reactions called the opposite of Combination reactions? Write equations for decomposition reactions.

Solution:

Combination reaction is said to be the reaction between two or more molecules to form a larger molecule; whereas the decomposition reaction is defined as the splitting of larger molecules into two or more smaller molecules. This essentially explains that the decomposition reaction is the opposite of the combination reaction.

In most of the cases the decomposition reaction is endothermic since heat from the surrounding or induced heat is used to break the bonds of the larger molecule. Few examples of decomposition reactions are:

ZnCO3 → ZnO + CO2

CaCO3 + Energy → CaO + CO2

2HgO → 2Hg + O2

12. Write one equation each for decomposition reactions in which energy is supplied in the form of heat, light or electricity.

Solution:

(a) Thermal decomposition reaction (Thermolysis)

Decomposition of potassium chlorate: When heated strongly, potassium chlorate decomposes into potassium chloride and oxygen. This reaction is used for the preparation of oxygen.

2KClO3 + Heat → 2KCl + 3O2

(b) Electrolytic decomposition reaction (Electrolysis)

Decomposition of sodium chloride: On passing electricity through molten sodium chloride, it decomposes into sodium and chlorine.

(c) Photodecomposition reaction (Photolysis)

Decomposition of hydrogen peroxide: In the presence of light, hydrogen peroxide decomposes into water and oxygen.

13.  What is the difference between displacement and double displacement reactions? Write relevant equations for the above.

Solution:

A displacement reaction is the one when a more reactive substance displaces a less reactive one from its salt solution whereas a double displacement reaction is the one where a mutual exchange of ions happens between two compounds.

In a displacement reaction, only a single displacement takes place whereas in the double displacement reaction, as the name suggests two displacement takes place between the molecules.

Example:

Displacement reaction

Mg + 2HCl → MgCl2 + H2

Double displacement reaction

2KBr + BaI2 → 2KI + BaBr2

14. In the refining of Silver, the recovery of silver from Silver nitrate solution involves displacement reaction by Copper metal. Write down the reaction involved.

Solution:

Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s)

15. What do you mean by a precipitation reaction? Explain by giving examples.

Solution:

When two solutions containing soluble salts are combined, a double displacement reaction takes place in which the ions are exchanged between the compounds. When one of such compounds formed is in solid form (that is insoluble in aqua) then it settles down at the bottom of the container. This solid is known as the precipitate and the respective reaction is termed as the precipitation reaction. Few examples of precipitation reactions are:

CdSO4(aq) + K2S(aq) → CdS(s) + K2SO4(aq)

2NaOH(aq) + MgCl2(aq) → 2NaCl(aq) + Mg(OH)2(s)

16. Explain the following in terms of gain of oxygen with two examples each.

(a) Oxidation

(b) Reduction

Solution:

(a) In a chemical reaction, when the oxygen is added to the element to form its respective oxide it is the element being oxidised. Example:

4Na(s) + O2(g) → 2Na2O(s)

H2S + O2 → H2O + SO2

(b) In a chemical reaction, when the oxygen is being removed from the compound then it is said to be reduced. Example:

CuO(s) + H2(g) → Cu(s) + H2O(l)

2HgO → 2Hg + O2

17. A shiny brown coloured element ‘X’ on heating in the air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.

Solution:

The shiny brown coloured element is the Copper metal (Cu). When the metal is heated in air, it reacts with atmospheric oxygen to form copper oxide. Hence, the black coloured compound is the copper oxide.

2Cu(s) + O2(g) → 2CuO(s)

18) Why do we apply paint on iron articles?

Solution:

Iron articles are painted to prevent them from rusting. When left unpainted, the metal surface comes in contact with the atmospheric oxygen and in the presence of moisture it from Iron(III) oxide. But if painted the surface does not come in contact with moisture and air thus preventing Rusting.

19) Oil and Fat containing food items are flushed with Nitrogen. Why?

Solution:

The main purpose of flushing Nitrogen into food packets that contain oil and fat items is to prevent Rancidity which occurs when the oil or fat reacts with the oxygen letting out an unpleasant smell and taste. Therefore, by flushing Nitrogen, an unreactive surrounding is created thus preventing rancidity.

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20) Explain the following terms with one example each.

(a) Corrosion

(b) Rancidity

Solution:

(a) Corrosion is a process where a refined metal is oxidised by atmospheric oxygen to form a more stable compound such as oxides. The metal gradually degrades during the corrosion process. Rusting of iron is a good example of corrosion where the iron is converted to Iron oxide. Millions of dollars are spent annually in preventing rusting from bridges and other monuments.

(b) The condition produced by the aerial oxidation of the oil and fat present in the food material that produces an unpleasant taste and smell. The rancidity is retarded when the food is kept inside the refrigerator since the low temperature does not promote the oxidation reaction.

                DR OMAR CLASSES BARRA KANPUR

CBSE Class 10 Science Notes Chapter 2 Acids Bases And Salts:

Introduction to Acids, Bases and Salts

Classification of matter

On the basis of
a) composition –  elements, compounds and mixtures
b) state – solids, liquids and gases
c) solubility – suspensions, colloids and solutions

Types of mixtures – homogeneous and heterogeneous
Types of compounds – covalent and ionic

To know more about Classification of Matter,

What Is an Acid and a Base?

Ionisable and non-ionisable compounds

An ionisable compound when dissolved in water or in its molten state, dissociates into ions almost entirely. Example: NaCl, HCl, KOH, etc.
A non-ionisable compound does not dissociate into ions when dissolved in water or in its molten state. Example: glucose, acetone, etc.

Arrhenius theory of acids and bases

Arrhenius acid – when dissolved in water, dissociates to give H⁺ (aq) or H₃O⁺ ion.
Arrhenius base – when dissolved in water, dissociates to give OH⁻ ion.

Examples

Acids 

• Hydrochloric acid (HCl)
• Sulphuric acid  (H₂SO₄)
• Nitric acid (HNO₃)

Bases

• Sodium hydroxide (NaOH)
• Potassium hydroxide (KOH)
• Calcium hydroxide (Ca(OH)₂)

To know more about Arrhenius Theory,

Bronsted Lowry theory

A Bronsted acid is an H⁺ (aq) ion donor.
A Bronsted base is an H⁺ (aq) ion acceptor.

Example

In the reaction: HCl (aq) + NH₃ (aq) → NH⁺₄(aq) + Cl⁻ (aq)
HCl – Bronsted acid and Cl⁻ : its conjugate acid
NH₃ – Bronsted base and NH⁺₄ : its conjugate acid

To know more about Bronsted Lowry Theory,

Physical test

Given are two possible physical tests to identify an acid or a base.

a. Taste

An acid tastes sour whereas a base tastes bitter.
The method of taste is not advised as an acid or a base could be contaminated or corrosive.

b. Effect on indicators by acids and bases

An indicator is a chemical substance which shows a change in its physical properties, mainly colour or odour when brought in contact with an acid or a base.
Below mentioned are commonly used indicators and the different colours they exhibit:

a) Litmus
In a neutral solution – purple
In acidic solution – red
In basic solution – blue

Litmus is also available as strips of paper in two variants – red litmus and blue litmus.
An acid turns a moist blue litmus paper to red.
A base turns a moist red litmus paper to blue.

b) Methyl orange
In a neutral solution – orange
In acidic solution – red
In basic solution – yellow

c) Phenolphthalein
In a neutral solution – colourless
In acidic solution – remains colourless
In basic solution – pink

Acid-Base Reactions

Reactions of acids and bases

a) Reaction of acids and bases with metals

Acid + active metal →  salt + hydrogen + heat

2HCl + Mg → MgCl₂ + H₂ (↑)

Base + metal → salt + hydrogen + heat

2NaOH + Zn → Na₂ZnO₂ + H₂ (↑)

A more reactive metal displaces the less reactive metal from its base.

2Na + Mg (OH) ₂ → 2NaOH + Mg

b) Reaction of acids with metal carbonates and bicarbonates

Acid + metal carbonate or bicarbonate →  salt + water + carbon dioxide.

2HCl + CaCO₃ → CaCl₂ + H₂O + CO₂
H₂SO₄ + Mg (HCO₃)₂ → MgSO₄ + 2H₂O + 2CO₂

Effervescence indicates liberation of CO₂ gas.

c) Neutralisation reaction

1. Reaction of metal oxides and hydroxides with acids
Metal oxides or metal hydroxides are basic in nature.
Acid + base → salt + water + heat

H₂SO₄ + MgO → MgSO₄ + H₂O
2HCl + Mg (OH) ₂ → MgCl₂ + 2H₂O

2. Reaction of non-metal oxides with bases

Non-metal oxides are acidic in nature
Base + Nonmetal oxide →  salt + water + heat

2NaOH + CO₂→ Na₂CO₃ + H₂O

To know more about Properties of Acids and Base

Water

Acids and bases in water

When added to water, acids and bases dissociate into their respective ions and help in conducting electricity.

Difference between a base and an alkali

Base:

• Bases undergo neutralisation reaction with acids.
• They are comprised of metal oxides, metal hydroxides, metal carbonates and metal bicarbonates.
• Most of them are insoluble in water.

Alkali:

• An alkali is an aqueous solution of a base, (mainly metallic hydroxides).
• It dissolves in water and dissociates to give OH⁻ ion.
• All alkalis are bases, but not all bases are alkalis.

To know more Difference between a base and an alkali,

Hydronium ion

Hydronium ion is formed when a hydrogen ion accepts a lone pair of electrons from the oxygen atom of a water molecule, forming a coordinate covalent bond.

 

Dilution

Dilution is the process of reducing the concentration of a solution by adding more solvent (usually water) to it.
It is a highly exothermic process.
To dilute acid, the acid must be added to water and not the other way round.

Strength of acids and bases

Strong acid or base: When all molecules of a given amount of an acid or a base dissociate completely in water to furnish their respective ions, H⁺(aq) for acid and OH⁻(aq) for base).
Weak acid or base: When only a few of the molecules of a given amount of an acid or a base dissociate in water to furnish their respective ions, H⁺(aq) for acid and OH⁻(aq) for base).
Dilute acid: contains less number of H⁺(aq) ions per unit volume.
Concentrated acid: contains more number of H⁺(aq) ions per unit volume.

 

Universal indicator

A universal indicator has a pH range from 0 to 14 that indicates the acidity or alkalinity of a solution.
A neutral solution has pH=7

pH

pH=−log₁₀[H⁺]
In pure water, [H⁺]=[OH⁻]=10⁻⁷ mol/L. Hence, the pH of pure water is 7.
The pH scale ranges from 0 to 14.
If pH < 7 → acidic solution
If pH > 7→ basic solution

 

pH scale

Importance of pH in everyday life

1. pH sensitivity of plants and animals

Plants and animals are sensitive to pH. Crucial life processes such as digestion of food, functions of enzymes and hormones happen at a certain pH value.

2. pH of a soil

The pH of a soil optimal for the growth of plants or crops is 6.5 to 7.0.

3. pH in the digestive system

The process of digestion happens at a specific pH in our stomach which is 1.5 to 4.
The pH of the interaction of enzymes, while food is being digested, is influenced by HCl in our stomach.

4. pH in tooth decay

Tooth decay happens when the teeth are exposed to an acidic environment of pH 5.5 and below.

5. pH of self-defence by animals and plants

Acidic substances are used by animals and plants as a self-defence mechanism. For example, bee and plants like nettle secrete a highly acidic substance for self-defence. These secreted acidic substances have a specific pH.

To know more about pH,

Manufacture of Acids and Bases

Manufacture of acids and bases

a) Nonmetal oxide + water → acid

SO₂(g) + H₂O(l) → H₂SO₃(aq)
SO₃(g) + H₂O(l) → H₂SO₄(aq)
4NO₂(g) + 2H₂O(l) + O₂(g) → 4HNO₃(aq)

Non-metal oxides are thus referred to as acid anhydrides.

b) Hydrogen + halogen → acid

H₂(g) + Cl₂(g) → 2HCl(g)
HCl(g) + H₂O(l) → HCl(aq)

c) Metallic salt + conc. sulphuric acid → salt + more volatile acid
2NaCl(aq) + H₂SO₄(aq) → Na₂SO₄(aq) + 2HCl(aq)
2KNO₃(aq) + H₂SO₄(aq) → K₂SO₄(aq) + 2HNO₃(aq)

d) Metal + oxygen → metallic oxide (base)
4Na(s) + O₂(g) → 2Na₂O(s)
2Mg(s) + O₂(g) → 2MgO(s)

e) Metal + water → base or alkali + hydrogen
Zn(s) + H₂O(steam) → ZnO(s)+ H₂(g)

f) Few metallic oxides + water → alkali
Na₂O(s) + H₂O(l) → 2NaOH(aq)

g) Ammonia + water → ammonium hydroxide
NH₃(g) + H₂O(l) → NH₄OH(aq)

Salts

Salts

A salt is a combination of an anion of an acid and a cation of a base.

Examples – KCl, NaNO₃ ,CaSO₄, etc.

Salts are usually prepared by the neutralisation reaction of an acid and a base.

Common salt

Sodium Chloride (NaCl) is referred to as common salt because it’s used all over the world for cooking.

Family of salts

Salts having the same cation or anion belong to the same family. For example, NaCl, KCl, LiCl.

pH of salts

A salt of a strong acid and a strong base will be neutral in nature. pH = 7 (approx.).
A salt of a weak acid and a strong base will be basic in nature. pH > 7.
A salt of a strong acid and a weak base will be acidic in nature. pH < 7.
The pH of a salt of a weak acid and a weak base is determined by conducting a pH test.

To know more about Salt, 

Preparation of Sodium hydroxide

Chemical formula – NaOH
Also known as – caustic soda

Preparation (Chlor-alkali process):
Electrolysis of brine (solution of common salt, NaCl) is carried out.
At anode: Cl₂ is released
At cathode: H₂ is released
Sodium hydroxide remains in the solution.

Bleaching powder

Chemical formula – Ca(OCl)Cl or CaOCl₂
Preparation – Ca(OH)₂(aq)+Cl₂(g)→CaOCl₂(aq)+H₂O(l)

On interaction with water – bleaching powder releases chlorine which is responsible for bleaching action.

Baking soda

Chemical name – Sodium hydrogen carbonate
Chemical formula – NaHCO₃

Preparation (Solvay process):
a. Limestone is heated: CaCO₃→CaO+CO₂
b. CO₂ is passed through a concentrated solution of sodium chloride and ammonia:
NaCl(aq)+NH₃(g)+CO₂(g)+H₂O(l)→NaHCO₃(aq)+NH₄Cl(aq)

Uses:
1. Textile industry
2. Paper industry
3. Disinfectant

Washing soda

Chemical name – Sodium hydrogen carbonate
Chemical formula – NaHCO₃
Preparation (Solvay process) – 
a. Limestone is heated: CaCO₃ → CaO + CO₂
b. CO₂ is passed through a concentrated solution of sodium chloride and ammonia:
NaCl(aq) + NH₃(g) + CO₂(g) + H₂O(l) → NaHCO₃(aq) + NH₄Cl(aq)

Uses
1. In glass, soap and paper industries
2. Softening of water
3. Domestic cleaner

Crystals of salts

Certain salts form crystals by combining with a definite proportion of water. The water that combines with the salt is called water of crystallisation.

Plaster of paris

Gypsum, CaSO₄.2H₂O (s) on heating at 100°C (373K) gives CaSO₄. ½ H₂O and 3/2 H₂O
CaSO₄. ½ H₂O is plaster of paris.
CaSO₄. ½ H₂O means two formula units of CaSO₄ share one molecule of water.
Uses – cast for healing fractures.

To know more about Plaster of Paris, Baking Soda and Washing Soda,

Frequently Asked Questions on Acids, Bases and Salts

When dissolved in water, Arrhenius base is a compound that ……….?

An Arrhenius base is a compound that increases the concentration of OH­^– ions that are present when added to water.

A solution X has a pH value of 2 and another solution Y has a pH value of 1. What can be inferred regarding the difference in hydrogen ion concentration between them?

pH is a measure of hydrogen ion concentration in a solution. Higher the hydrogen ion concentration, lower is the pH. Acids which give rise to more hydrogen ions are more acidic than the acids which give less hydrogen ions. Thus, lower the pH, higher is the acidic nature of the solution. Thus, Y has more hydrogen ion concentration than X.

Dilute hydrochloric acid (HCl) reacts with metals to evolve __ gas along with the formation of corresponding metal salt.

Acids react with metals to produce the respective metal salt along with hydrogen gas. Therefore, when hydrochloric acid (HCl) reacts with metals it evolve hydrogen gas along with the formation of corresponding metal salt.

 

                      DR OMAR CLASSES BARRA KANPUR

NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts

NCERT Solutions For Class 10 Science Chapter 2 Acids And Bases:  In this article, we will provide you with NCERT Solutions For Class 10 Science Chapter 2 Acids And Bases. Having proper knowledge of the theories, sufficient practice of the reactions, equations and formulas, and solving questions from the NCERT Chemistry books are very important if you want to score well in Science for Class 10 board exams as well as JEE and NEET. Going through the step-wise solutions for every question too is highly important to bag a good score.

Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts

NCERT Solutions For Class 10 Science Chapter 2 Notes for Acids And Bases has been provided by India’s topmost Chemistry teachers. Also in this article, you will find the Step-wise explanation for each and every question. Going through them will help you in getting a better understanding of how to solve problems. Read on to find out NCERT Solutions for Class 10 Science Chapter 2 Exercise and Extra Questions.

NCERT Solutions for Class 10 Science Chapter 2 Acids and Bases

Before getting into the details of NCERT Solutions For Class 10 Science Chapter 2 Acids And Bases, let’s have an overview of topics & subtopics under NCERT Solutions for Class 10 Science Chapter 2 Activities:

1.    Acids, Bases And Salts

2.    Understanding The Chemical Properties Of Acids And Bases

3.    What Do All Acids And All Bases Have In Common?

4.    How Strong Are Acid Or Base Solutions?

5.    More About Salts

Free download NCERT Solutions for Class 10 Science Chapter 2 Acids And Bases PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

NCERT Solutions for Class 10 Science Chapter

Page Number: 18

Question 1
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube ?
Answer:
(i) Put the red litmus paper in all the test tubes, turn by turn. The solution which turns red litmus to blue will be a basic solution. The blue litmus paper formed here can now be used to test the acidic solution.
(ii) Put the blue litmus paper obtained above in the remaining two test-tubes, turn-by-turn. The solution which turns the blue litmus paper to red will be the acidic solution.

(iii) The solution which has no effect on any litmus paper will be neutral and hence it will be distilled water.

Page Number: 22

Question 1
Why should curd and sour substances not be kept in brass and copper vessels ?
Answer:
Curd and sour substances should not be kept in brass and copper vessels because these and other sour food-stuffs contain acids which can react with the metal of the vessel to form poisonous metal compounds which can cause food poisoning and affect our health adversely.

Question 2
Which gas is usually liberated when an acid reacts with a metal ? Illustrate with an example. How will you test for the presence of this gas ?
Answer:
(i) Hydrogen (H₂) gas is liberated when an acid reacts with a metal.
(ii) Illustration : Set up the apparatus as shown in the given figure. Take some zinc granules in the test tube. Add about 5 mL dilute hydrochloric acid slowly. Soon the reaction between zinc and hydrochloric acid starts and hydrogen gas is evolved.

(iii) Test for H₂ gas :
H₂ gas is not soluble in water. When passed through soap solution, it gets trapped into bubbles.
Bring a burning candle near the soap bubble filled with gas. The soap bubble bursts and hydrogen gas burns with a pop sound.

Question 3
Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.
Answer:
As the end product is calcium chloride and the gas formed is carbon dioxide, the metal compound A must be calcium carbonate. Therefore, the reaction between calcium carbonate and hydrochloric acid is

Page Number: 25

Question 1
Why do HCl, HNO₃, etc show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character ?
Answer:
H⁺ ions in aqueous solution are responsible for acidic character. HCl, HNO₃, etc. give H⁺ ions in water while alcohol and glucose do not give H⁺ ion in water. Therefore, alcohol and glucose do not show acidic character.

Question 2
Why does an aqueous solution of an acid conduct electricity ?
Answer:
The aqueous solution of an acid conducts electricity due to the presence of charged particles called ions in it.

Question 3
Why does dry HCl gas not change the colour of the dry litmus paper ?
Answer:
Dry HCl gas does not give H⁺ ions and therefore does not change the colour of dry litmus paper.

Question 4
While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid ?
Answer:
While diluting an acid it is recommended that the acid should be added to water and not water to the acid because if water is added to concentrated acid to dilute it, then a large amount of heat is evolved at once. This heat changes some of the water to steam explosively which can splash the acid on one’s face or clothes and cause acid burns.

Question 5
How is the concentration of hydronium ions (H₃O⁺) affected when a solution of an acid is diluted ?
Answer:
When a given amount of an acid is added to water, there is a fixed number of hydronium ions per volume of the solution. On dilution, the number of hydronium ions per volume decreases and concentration decreases.

Question 6
How is the concentration of hydroxide ions (OH^–) affected when excess base is dissolved in a solution of sodium hydroxide ?
Answer:
The concentration of hydroxide ions will increase when excess base is dissolved in a solution of sodium hydroxide, but it happens to a limited extent only after which the concentration becomes almost constant.

Page Number: 28

Question 1
You have two solutions A and B. The pH of solution A is 6 and pH of solution B is 8. Which solution has more hydrogen ion concentration? Which of this is acidic and which one is basic ?
Answer:
A pH value of less than 7 indicates an acidic solution, while greater than 7 indicates a basic solution. Since solution A has more hydrogen ion concentration, solution A is acidic and solution B is basic.

Question 2
What effect does the concentration of H⁺ (aq) ions have on the nature of the solution ?
Answer:
More the concentration of H⁺ ions, higher the acidic nature of the solution.

Question 3
Do basic solutions also have H⁺ (aq) ions ? If yes, then why are these basic ?
Answer:
Basic solutions have H⁺ (aq) ions. But these are far less in number than OH^– ions that is responsible for their basic nature.

Question 4
Under what soil condition do you think a farmer would treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate) ?
Answer:
If the soil is too acidic (having low pH) then it is treated with materials like quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate).

Page Number: 33

Question 1
What is the common name of the compound CaOCl₂ ?
Answer:
Bleaching powder.

Question 2
Name the substance which on treatment with chlorine yields bleaching powder.
Answer:
Slaked lime Ca (OH)₂.

Question 3
Name the sodium compound which is used for softening hard water.
Answer:
Sodium carbonate.

Question 4
What will happen if a solution of sodium hydrogen carbonate is heated. Give the equation of the reaction involved ?
Answer:
Solution of sodium hydrogen carbonate on heating gives sodium carbonate and carbon dioxide gas is evolved.

Question 5
Write an equation to show the reaction between plaster of Paris and water.
Answer:

NCERT Solutions for Class 10 Science Chapter 2 Textbook Chapter End Questions

Question 1
A solution turns red litmus blue, its pH is likely to be
(a) 1
(b) 4
(c) 5
(d) 10
Answer:
(d) 10

Question 2
A solution reacts with crushed-egg shells to give a gas that turns lime water milky. The solution contains
(a) NaCl
(b) HCl
(c) LiCl
(d) KCl
Answer:
(b) HCl

Question 3
10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HC1. If we take 20 mL of the same solution of NaOH, the amount of HC1 solution (the same solution as before) required to neutralise it will be
(a) 4 mL
(b) 8 mL
(c) 12 mL
(d) 16 mL
Answer:
(d) 16 mL

Question 4
Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic
Answer:
(c) Antacid

Question 5
Write word equations and then balanced equations for the reaction taking place when
(a) dilute sulphuric acid reacts with zinc granules
(b) dilute hydrochloric acid reacts with magnesium ribbon
(c) dilute sulphuric acid reacts with aluminium powder
(d) dilute hydrochloric acid reacts with iron filing
Answer:
(a) Zinc + dilute sulphuric acid → Zinc sulphate + Hydrogen
Zn (s) + H₂SO₄ (aq) → ZnSO₄ (aq) + H₂ (g)

(b) Magnesium ribbon + dil. Hydrochloric acid → Magnesium chloride + Hydrogen
Mg (s) + 2 HCl (aq) → MgCl₂ (aq) + H₂ (g)

(c) Aluminium powder + dil. Sulphuric acid > Aluminium sulphate + Hydrogen
2Al (s) + 3H₂SO₄ (aq) → Al₂ (SO₄)₃ (aq) + 3H₂ (g)

(d) Iron filings + Dilute hydrochloric acid > Ferric chloride + Hydrogen
2Fe (s) + 6HCl (aq) → 2FeCl₃ (aq) + 3H₂ (g)

Question 6
Compounds such as alcohol and glucose also contain hydrogen but are not categorised as acids. Describe an activity to prove it.
Answer:
Though compounds like alcohol and glucose contain hydrogen but they do not ionise in the solution to produce H⁺ ions on passing current through them.
(i) Take solutions of alcohols and glucose.
(ii) Fix two nails on a cork, and place the cork in 100 mL beaker.
(iii) Connect the nails to the two terminals of a 6 volt battery through a bulb and a switch, as shown in the given Figure.

(iv) Now pour alcohol in the beaker and switch on the current.
(v) The bulb does not glow.
(vi) Repeat the experiment with glucose. The bulb does not glow in this case also.
(vii) This means no ions or H+ ions are present in the solution.
This shows that alcohols and glucose are not acids.

Question 7
Why does distilled water not conduct electricity, whereas rainwater does ?
Answer:
Distilled water does not conduct electricity because it does not contain any ionic compound (like acids, bases or salts) dissolved in it.
Rainwater, while falling to the earth through the atmosphere, dissolves an acidic gas carbon dioxide from the air and forms carbonic acid (H₂CO₃). Carbonic acid provides hydrogen ions, H⁺ (aq) and carbonate ions, CO(aq)₃²to rainwater. Hence, due to the presence of carbonic acid which provides ions to rainwater, the rainwater conducts electricity.

Question 8
Why do acids not show acidic behaviour in the absence of water ?
Answer:
The acidic behaviour of acids is due to the presence of hydrogen ions, [H⁺ (aq) ions], in them. The acid produces hydrogen ions only in the presence of water. So in the absence of water, an acid will not form hydrogen ions and hence will not show its acidic behaviour.

Question 9
Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9 respectively. Which solution is
(a) Neutral
(b) Strongly alkaline
(c) Strongly acidic
(d) Weakly acidic
(e) Weakly alkaline
Arrange the pH in increasing order of hydrogen ion concentration.
Answer:
(a) D
(b) C
(c) B
(d) A
(e) E
Increasing order of hydrogen ion concentration
11 < 9 < 7 < 4 < 1
i. e., C < E < D < A < B

Question 10
Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH₃COOH) is added to test tube B. In which test tube will the fizzing occur more vigorously and why ?
Answer:
Fizzing will occur more vigorously in test tube A. Hydrochloric acid (HCl) is a strong acid whereas acetic acid (CH₃COOH) is a weak acid. Being strong acid, the hydrochloric acid solution contains a much greater amount of hydrogen ions in it due to which the fizzing will occur more vigorously in test tube A (containing hydrochloric acid). The fizzing is due to the evolution of hydrogen gas which is formed by the action of acid on the magnesium metal of magnesium ribbon.

Question 11
fresh milk has a pH of 6. How do you think the pH will change as it turns into curd ? Explain your answer.
Answer:
pH of milk falls below 6 as it turns into curd due to the formation of lactic acid during this process. Lactic acid present in it reduces its pH value.

Question 12
A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline ?
(b) Why does this milk take a long time to set as curd ?
Answer:
(a) Milk is made slightly alkaline so that it may not get sour easily due to the formation of lactic acid in it.
(b) The alkaline milk takes a longer time to set into curd because the lactic acid being formed has to first neutralise the alkali present in it.

Question 13
Plaster of Paris should be stored in a moisture proof container. Explain why?
Answer:
Plaster of Paris should be stored in a moisture proof container because the presence of moisture can cause slow setting of plaster of Paris by bringing about its hydration. This will make the plaster of Paris useless after sometime.

Question 14
What is a neutralisation reaction ? Give two examples.
Answer:
The reaction between an acid and a base to form salt and water is called a neutralisation reaction.
Examples:

Question 15
Give two important uses of washing soda and baking soda.
Answer:
Uses of washing soda :
(i) Washing soda is used in glass, soap and paper industries.
(ii) It is used for removing permanent hardness of water.

Uses of baking soda :
(i) Baking soda is used as an antacid in medicines to remove acidity of the stomach.
(ii) Baking soda is used for making baking powder (used in making cakes, bread, etc.).

NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases, and Salts

NCERT Solutions for Class 10 Science (Chemistry) Chapter 2 Acids, bases, and salts are part of NCERT Solutions for Class 10 Science. Here we have given Class 10 Science NCERT Solutions Chapter 2.

Question 1
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
Solution:
The contents of each test tube would be identified by change in colour of red litmus paper. For example, when we wet the red litmus paper with the basic solution, it changes into blue colour. Put the changed blue litmus paper in the solution which turns the blue to red will be the acidic solution. The solution, which has no effect on any litmus paper, will be neutral and hence it will be distilled water.

Question 2
Why should curd and sour substances not be kept in brass and copper vessels?
Solution:
Curd and other sour foodstuffs contain acids, which can react with the metal of the vessel to form poisonous metal compounds which can cause food poisoning and damage our health.

Question 3
Which gas is usually liberated when an acid reacts with a metal?
Solution:
When an acid reacts with metal, a salt and hydrogen gas is formed. i.e

Question 4
Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.
Solution:
The gas that extinguishes a burning candle is carbon dioxide, which is formed by the action of dilute hydrochloric acid on a metal carbonate and produces effervescence. Now, since one of the compounds formed is calcium chloride, it shows that the metal compound is calcium carbonate. Thus, the metal compound A is calcium carbonate (CaCO₃). Calcium carbonate reacts with dilute hydrochloric acid to form calcium chloride, carbon dioxide and water. This can be written as:

Question 5
Why do HCl, HNO₃, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?
Solution:
An acid is a substance, which dissociates on dissolving in water to produce hydrogen ions [H⁺(aq) ions]. The acids like HCl, H₂SO₄, HNO₃ and CH₃COOH, etc., show acidic character because they dissociate in aqueous solutions to produce hydrogen ions, H+(aq) ions.
The compounds such as glucose and alcohol also contain hydrogen but they do not show acidic character. The aqueous solutions of glucose and alcohol do not show acidic character because the hydrogen in them does not separate out as hydrogen ions [H⁺ (aq) ions] on dissolving in water.

Question 6
Why does an aqueous solution of acid conduct electricity?
Solution:
The aqueous solution of an acid conducts electricity due to the presence of charged particles called ions in it.

Question 7
Why does dry HCl gas not change the colour of the dry litmus paper?
Solution:
Dry HCl gas does not contain any hydrogen ions in it, so it does not show acidic behaviour. In fact, dry HCl gas does not change the colour of dry litmus paper as it has no hydrogen ions [H⁺(aq) ions] in it.

Question 8
While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
Solution:
Diluting an acid should be done by adding concentrated acid to water gradually with stirring and not by adding water to concentrated acid.
The heat is evolved gradually when a concentrated acid is added to water for diluting an acid and the large amount of water is easily absorbed.
If, however, water is added to concentrated acid to dilute it, a large amount of heat is evolved at once. The heat generated may cause the mixture to splash the acid on our face or clothes and cause acid burns.

Question 9
How is the concentration of hydronium ions (H₃O+) affected when a solution of an acid is diluted?
Solution:
When the concentrated solution of an acid is diluted by mixing water, the concentration of hydronium ions H₃O+ per unit volume decreases.

Question 10
How is the concentration of hydroxide ions (OH-) affected when excess base is dissolved in water?
Solution:
When the solution of a base is diluted by mixing more water in it, the concentration of hydroxide ions (OH^– ions) per unit volume decreases.

Question 11
You have two solutions A and B. The pH of solution A is 6 and pH of solution B is 8.
i. Which solution has more hydrogen ion concentration?
ii. Which of this is acidic and which one is basic?
Solution:
The pH of a solution is inversely proportional to its hydrogen ion concentration. This means that the solution having lower pH will have more hydrogen ion concentration. In this case, solution A(having a lower pH of 6) will have more hydrogen ion concentration.Solution A is acidic and solution B is basic.

Question 12
What effect does the concentration of H⁺(aq) ions have on the nature of the solution?
Solution:
Acids produce hydrogen ions in water. So, when an acid is added to water, the concentration of hydrogen ions in water increases. The solution of acid thus formed will have more of hydrogen ions and it will be acidic in nature.

Question 13
Do basic solutions also have H⁺(aq) ions? If yes, why are these basic?
Solution:
No, the basic solution doesn’t have H⁺ ions as the solution has excess of hydroxide ions.

Question 14
Under what soil condition do you think a farmer would treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate)?
Solution:
Most often the soil in the fields is too acidic. If the soil is too acidic (having low pH), it is treated with materials like quicklime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate). Thus, a farmer should add lime or slaked lime in his fields when the soil is too acidic.

Question 15
What is the common name of the compound CaOCl₂?
Solution:
The common name of the compound CaOCl₂ is bleaching powder.

Question 16
Name the substance that on treatment with chlorine yields bleaching powder.
Solution:
Calcium hydroxide is the substance that on treatment with chlorine yields bleaching powder.

Question 17
Name the sodium compound, which is used, for softening hard water.
Solution:
Sodium carbonate (washing soda) is used for softening hard water.

Question 18
What will happen if a solution of sodium hydro carbonate is heated? Give the equation of the reaction involved.
Sodium carbonate and carbon dioxide are evolved when sodium hydro carbonate is heated.

Question 19
Write an equation to show the reaction between plaster of Paris and water.
Solution:
Plaster of Paris has a very remarkable property of setting into a hard mass on wetting with water. So, when water is added to plaster of Paris, it sets into a hard mass in about half an hour. The setting of plaster of Paris is due to the hydration crystals of gypsum, which set to form a hard, solid mass.

Question 20
Why does distilled water not conduct electricity, whereas rainwater does?
Solution:
Distilled water does not conduct electricity because it does not contain any ionic compound (like acids, bases or salts) dissolved in it. On the other hand, rain water conducts electricity. This can be explained as follows: Rain water, while falling to the earth through the atmosphere, dissolves an acidic gas carbon dioxide from the air and forms carbonic acid (H₂CO₃). Carbonic acid provides hydrogen ions, H⁺(aq), and carbonate ions, CO^2-₃ (aq), to rain water. So, due to the presence of carbonic acid (which provides ions to rain water), the rain water conducts electricity.

Question 21
Why do acids not show acidic behaviour in the absence of water?
Solution:
The acidic behaviour of acid is due to the presence of hydrogen ions. The acids will not show its acidic behaviour in the absence of water, this is because the acids produce hydrogen ions only in the presence of water.

Question 22
Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9 respectively. Which solution is?
(i) Neutral?
(ii) Strongly alkaline?
(iii) Strongly acidic?
(iv) Weakly acidic?
(v) Weakly alkaline? Arrange the pH in increasing order of hydrogen-ion concentration.
Solution:

Question 23
Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test-tube A while acetic acid (CH₃COOH) is added to test-tube B. In which test-tube will fizzing occur more vigorously and why?
Solution:
Acetic acid (CH₃COOH) is a weak acid whereas hydrochloric acid (HCl) is a strong acid. Fizzing occurs in the test tube due to the evolution of hydrogen gas by the action of acid on magnesium ribbon. Since hydrochloric acid is a strong acid a large amount of hydrogen gas is liberated in the test tube A. So fizzing occurs more vigorously in test tube A .
Question 24
Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain.
Solution:
The pH will change to below 6, as lactic acid is formed when milk turns into curd.

Question 25
Plaster of Paris should be stored in a moisture-proof container. Why?
Solution:
The presence of moisture can affect the slow setting of plaster of Paris by bringing about its hydration. This will make the plaster of Paris useless after some time.
Question 26
What is a neutralization reaction? Give two examples.
Solution:
The reaction of an acid and a base, giving rise to the corresponding salt and water is called neutralization reaction.
Examples:
NaOH + HCl → NaCl + H₂O
Mg(OH)₂ + H₂CO₃ → MgCO₃ + 2H₂O

Question 27
Give two important uses of washing soda and baking soda.
Solution:
Washing soda
1. It is often used as an electrolyte.
2. Domestically it is used as a water softener during laundry.
Baking soda
1. It is used to test garden soil for acidity. If it develops bubbles, the soil is too acidic.
2. Washing a car with it can remove dead bug bodies without damaging the paint.

NCERT Solutions for Class 10 Science Chapter 2 (MCQs) [1 Mark each]

Question 1.
Equal pieces of zinc granules are dropped in four test tubes. Following substances are poured in all the four test tubes. The reaction will be vigorous with [CCE 2014]
(a) CH₃COOH
(b) HCl
(c) sodium bicarbonate solution
(d) lemon juice
Answer:
(b) Strong adds like HCl react vigorously with active metals like Zn and form metal salt and evolve H₂ gas.

Question 2.
Which of the following statements shows the property of an acid? [CCE 2014]
(a) It turns blue litmus to red
(b) It is sour in taste
(c) It has no effect on red litmus
(d) All of the above
Answer:
(d) An acid turns blue litmus red. Thus, it has no effect on red litmus and acids are sour in taste.

Question 3.
A drop of a liquid sample was put on the pH paper. It was observed that the colour of the pH paper turned blue. The liquid sample is [CCE 2014]
(a) lemon juice
(b) sodium bicarbonate solution
(c) distilled water
(d) hydrochloric acid
Answer:
(b) The liquid sample is of sodium bicarbonate (NaHC₃) solution. It is a basic solution. And we know that a basic solution turns pH paper blue.

Question 4.
Two solutions X and Y were found to have pH value of 4 and 10 respectively. The inference that can be drawn is [CCE 2014]
(a) X is a base and Y is an acid
(b) Both X and Y are acidic solutions
(c) X is an acid and Yis a base
(d) Both X and Y are bases
Answer:
(c) Any solution having pH > 7 will be a base while the solution having pH < 7 will surely be an acid. Hence, it can be concluded that X is an acid (pH=4, i.e. < 7) and Yis a base (pH =10, i.e. > 7).

Question 5.
A student was asked to collect apparatus from lab store, for doing experiment of pH of given sample. Identify the article which he is not supposed to pick. [CCE 2014]
(a) pH paper
(b) Dropper
(c) Litmus paper
(d) Petri dish
Answer:
(d) Petri dish is not required for doing experiment of pH.

Question 6.
Which one of the following would you need to identify the gas that evolve when you heat NaOH solution with zinc metal? [CCE 2014]
(a) Red litmus solution
(b) Blue litmus solution
(c) A burning splinter / matchstick
(d) Lime water
Answer:
(c) When a base like NaOH is treated with any active metal like Zn, it produces H₂ gas. And the presence of the hydrogen gas can be tested by bringing a burning splinter/ matchstick near the gas produced. The gas will burn with a pop sound confirming the presence of hydrogen gas.

Question 7.
A solution has pH value of 5. On adding 10 mL of NaCl to it, what will be the pH of the new solution?
(a) More than 5
(b) Less than 5
(c) Only seven
(d) No change in pH
Answer:
(d) As NaCl is a neutral solution due to its complete ionization in H₂O and has pH = 7. Thus, it will not affect the pH of the solution. Hence, the pH of the solution will remain unaffected.

Question 8.
A salt is dissolved in water. The pH of this salt solution was found to be 7 by measuring the pH with a universal indicator paper. The salt is most likely to be
(a) Na₂CO₃
(b) KCl
(c) NH₄Cl
(d) CH₃COONa
Answer:
(b) Salts which are completely ionisable in water are said to be neutral salts and their pH is equal to 7. Among the given salts, only KCl is completely ionisable in the following manner: KCl (aq) → K⁺ + Cl
Hence, the pH of KCl will be 7.

Question 9.
A student performed an experiment using zinc granules and sodium carbonate with sodium hydroxide and hydrochloric acid under different
conditions as shown below.

In which set up, no gas is evolved?
(a) I
(b) II
(c) III
(d) IV
Answer:
(d) Gas will not evolve in the case of IV set up as NaOH does not react with sodium carbonate.

Question 10.
Four set ups as given below are arranged to identify the gas evolved when dilute hydrochloric acid was added to zinc granules. Which is the most appropriate set up?

(a) I
(b) II
(c) IV
(d) III
Answer:
(c) The gas evolved can be tested as shown in IV set up because to evolve H₂ gas delivery tube, should not dip in the acid.

Question 11.
Four students I, II, III and IV were asked to examine the changes for blue and red litmus paper strips with dil. HCl (Solution A) and dil. NaOH (Solutions). The following observations were reported by the 4 students. The sign …………. indicates no colour change. [CCE 2015 ]

	Litmus	A	B	Litmus	A	B
I	Blue	—	red	Blue	red	—
II	Red	—	blue	Red	—	blue
III	Blue	red	red	Blue	blue	blue
IV	Red	blue	blue	Red	red	red

The correct observation would be of student
(a) I
(b) II
(c) III
(d) IV
Answer:
(c) The correct observation is taken by student III because HCl (solution A) is an acid which turns blue litmus red and dil. NaOH (solution B) is a base which turns red litmus blue.

Question 12.
A sample of soil is mixed with water and allowed to settle. The clear supernatant solution turns the pH paper yellowish orange. Which of the following would change the colour of this pH paper to greenish blue? [NCERT Exemplar]
(a) Lemon juice
(b) Vinegar
(c) Common salt
(d) An antacid
Answer:
(d) As pH paper turns greenish blue for weakly basic compound and antacids contain weak base like Mg(OH)₂. So, an antacid would change the colour of this pH paper to greenish blue. Other options (a) and (b) contain acids and option (c) is a neutral salt.

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Life Process

Introduction Life

 Earth happens to be the only known planet having life. There are beings which live, die and become part of nature again. The living organism can be differentiated from the inanimate entities on various parameters of life processes.

Life Process

 Maintenance of living organism is essential even if they are moving, resting or even sleeping. The processes which together perform the function of maintenance of 'life' are called as life processes. Nutrition, respiration, circulation, excretion are the examples of essential life processes. In unicellular organisms, all these processes are carried out by that single cell. In multicellular organisms, well-developed systems are present to carry out the processes.

Nutrition

The process of acquiring food that is needed for nourishment and sustenance of the organism is called nutrition. There are two main modes of nutrition, autotrophic and heterotrophic. Heterotrophic nutrition has subtypes as holozoic, saprophytic and parasitic nutrition.

Autotrophic Nutrition

If an organism can nourish itself by making its own food using sunlight or chemicals such mode of nutrition is called as autotrophic nutrition. Plants photosynthesize (use light energy) and are called photoautotrophs. Few bacteria use chemicals to derive energy and are called chemoautotrophs.

Photosynthesis

Photosynthesis is the important process by which food is formed. Life Processes The plants make food using sunlight and water, which provides nourishment to other organism and themselves. Chlorophyll present in the green parts absorbs light energy. This light energy is used to split water into hydrogen and oxygen. Hydrogen is then used to reduce carbon dioxide into carbohydrates, typically glucose. Chlorophyll is essential for photosynthesis and stomata facilitate intake of carbon dioxide.

 

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Stomata

 Stomata are pores on the leaves that help in exchange of gases. They are mostly found on the underside of the leaf. Each stoma is guarded by guard cells, which control the opening and closing of the pore. The water content of the guard cells is responsible for their function.

 Stoma in open and closed state(Diagramm)

Saprophytic Nutrition

 Some organism feed on dead and decaying organic matter. This mode of nutrition is called saprophytic nutrition. The food is partially digested outside the body and then it is absorbed. E.g. Fungi are saprophytes.

Parasitic Nutrition

Some organisms feed on the expense of another organism and in turn causing it harm. This is called parasitic mode of nutrition. These organisms live on the body or in the body of a host organism and derive the nutrients directly from the body of the host. E.g. Leech is an ectoparasite while Ascaris is an endoparasite. Cuscuta is a parasitic plant.

Nutrition in Amoeba

Amoeba feeds by holozoic mode of nutrition. It engulfs the food particle using pseudopodia, the process is called as phagocytosis. The engulfed food gets enclosed in a food vacuole. As the food vacuole passes through the cytoplasm, digestion, absorption and assimilation take place. When the food vacuole opens to outside, egestion of undigested food takes place.

 Holozoic Nutrition in Amoeba(Diagramm)

Nutrition in Paramoecium

 Paramoecium also exhibit holozoic nutrition. However, they have cilia that help them to engulf the food through the oral groove. A food vacuole is created enclosing the food. It moves through the cytoplasm, the process is called cyclosis. Food digested in the food vacuole is absorbed by the cytoplasm. Undigested food is given out to a tiny pore called anal pore or cytopyge.

 Intracellular digestion in Paramecium(Diagramm)

 

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Nutrition in Humans

Humans are omnivores, they can eat plant-based food as well as animal-based food. Being more complex, humans have a very complicated nutrition system. The digestive system has an alimentary canal and associated digestive glands, which together function to nourish the body. There are five stages in human nutrition; Ingestion, Digestion, Absorption, Assimilation and Egestion. Four stages i.e. ingestion, digestion, absorption and egestion take place in the alimentary canal while assimilation of food takes place in the whole body

Alimentary Canal

Alimentary canal in humans is a long tube of varying diameter.  It starts with mouth and ends with the anus. Oesophagus, stomach, small intestine and large intestine are the parts of the alimentary canal.

Mouth

 It is the opening of the alimentary canal and helps in ingestion of food. The buccal cavity which is present behind the mouth is also commonly referred as mouth. The buccal cavity has teeth and tongue. The set of teeth helps in mastication of food. The tongue has taste buds on it and thus helps in tasting the food. The salivary glands open also in the buccal cavity and pour saliva which initiates the process of digestion.

Teeth

 Teeth are the hard structures present in the buccal cavity. They help us to cut, shear and masticate the food we eat. Vertical section of a tooth shows four layers as enamel, dentine, cement and dental pulp. Enamel is outermost, shiny, highly mineralized and hardest part of the human body. Dentine makes the bulk of the tooth and contains 70% inorganic salts. Cement is present at the lining of a tooth and bony socket. Dental pulp is the central soft part of a tooth and contains nerve endings, blood and lymph vessels along with connective tissue. There are four types of teeth in humans, Incisors, canines, molars and premolars, each with a specific function. Incisors cut the food, canines tear the food while molars and premolars crush it. The dental formula in adult humans is 2:1:2:3.

 Structure of a Tooth(Diagramm)

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Oesophagus & Stomach

Oesophagus

 The swallowed food passes into the oesophagus. It is a muscular tube, about 25 cm long, with a sphincter (valve/opening) at each end. Its function is to transport food and fluid, after being swallowed, from the mouth to the stomach. Food is pushed down by peristaltic movements.

Stomach

The stomach is thick-walled bag-like structure. Its receives food from the oesophagus at one end and opens into the small intestine at the other end. The inner lining of the stomach secretes mucus, hydrochloric acid and digestive juices. Food is churned into semi-solid mass in the stomach and is called chyme. Enzymes present in the gastric juice break down the food. Hydrochloric acid helps in partial digestion of proteins and also kills harmful bacteria. Mucus secreted by the wall of stomach resists the action of HCl on itself.

Small Intestine

The small intestine is the longest part of the alimentary canal, about 20 feet long in humans. It has regions, duodenum, the region which follows stomach, jejunum is the middle part and ileum is the later region which continues further into the large intestine. The internal surface of the small intestine is folded into finger-like projections called villi.  A common pancreatic duct from pancreas and liver opens into the duodenum. Most of the chemical digestion and absorption takes place in the small intestine.

Large Intestine

 Large intestine in humans is about 5 feet long. It has two regions, colon ( about 1.5 m) and rectum (10 cm in length in the adult). The region of large intestine after ileum is called colon while the last part is called rectum. Colon has three regions as, ascending colon, transverse colon and descending colon. At the base of ascending colon, a small finger-like out-growth is seen and is called an appendix. It houses many useful bacteria required for digestion of food. Rectum opens to outside by anus. The anus has internal and external anal sphincters. Small and Large Intestine(Diagramm)

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Peristalsis

A constant wave-like movement of the alimentary canal right from the oesophagus to the small intestine is called as peristalsis. Muscles present in the wall of the alimentary canal are responsible for peristalsis. This movement helps to push the food through the alimentary canal.

Digestive Glands

Several glands produce digestive juices that help in digestion of the food. Salivary glands, Gastric glands, Liver, Gallbladder, Pancreas are few to name. Salivary glands secrete saliva which initiates digestion in the mouth itself. Gastric glands present in the wall of the stomach secrete hydrochloric acid and enzyme pepsin. The liver secretes bile which is stored in the gallbladder. Bile helps in digestion of fats. The pancreas secretes many digestive enzymes and its secretion is called as pancreatic juice. Enzymes like trypsin, chymotrypsin, lipase, amylase are present in the pancreatic juice.

Pancreas

 The pancreas is a long, flat gland present behind the stomach in humans. It is one of the major digestive glands and is of mixed nature i.e. endocrine as well as exocrine. As an endocrine organ, it secretes two hormones called insulin and glucagon which maintain the blood sugar level. As an exocrine gland, it secretes pancreatic juice which is nothing but a mixture of many digestive enzymes. The digestive enzymes secreted by pancreas include trypsin and chymotrypsin and proteases which digest proteins. It also includes amylase which digests the starch content of the food. Pancreatic lipases are the pancreatic enzymes that help in digestion of fats. 

 Anatomy of Human Pancreas(Diagramm)

Holozoic Nutrition

 The mode of nutrition in which animals take their food as a whole is called as holozoic nutrition. In holozoic nutrition, food passes through five steps as ingestion, digestion, absorption, assimilation and egestion.

 

 

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Physiology of Digestion

Mechanical digestion of food takes place in the buccal cavity where teeth masticate the food, saliva gets mixed and it turns into a bolus. Digestion of starch starts in the buccal cavity itself, with the action of salivary amylase present in the saliva. Salivary amylase converts starch into maltose. In the stomach, the churning of food takes place due to the muscular contraction and relaxation of its wall. It breaks down the food into simpler substances. Digestion of proteins starts in the stomach with the action of pepsin. Proteins are broken down into smaller fragments called peptide by the action of pepsin. The bolus after mixing with gastric juice, turn into a fine soluble form known as the chyme. Chyme enters into the small intestine where complete digestion takes place due to the action of various enzymes present in the pancreatic juice, bile and intestinal juice. The digested food is completely absorbed by the villi and microvilli of the small intestine. Undigested food then enters into the large intestine.  Colon is responsible for absorption of water and salts whereas rectum stores the undigested food temporarily before defaecation

Digestive System in Other Animals

Digestive systems in different animals vary in structure and function. The structure of the digestive system depends on the food habits of the animal. Alimentary canal in herbivores is long as the cellulose content of their plant-based diet takes a long time to digest. On the other hand, alimentary canal of carnivorous animals is comparatively shorter because meat gets digested faster.

Anatomy of Digestive Tract

Alimentary canal in humans approximately 30 feet (9m) long. It starts with mouth and ends in the anus. Between these two openings, alimentary canal is the tube of varying diameter. Oesophagus, stomach, small intestine (divided into three regions as duodenum, jejunum and ileum) and large intestine(having two regions as colon and rectum) are the parts of the alimentary canal. Salivary glands, pancreas and liver act as major digestive glands. Glands present in the wall of the stomach and small intestine also contribute towards digestion of food.

 

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Role of HCl

 Hydrochloric acid in the stomach is secreted by the gastric glands present in its wall. pH of the gastric acid is usually between 1.5 to 3.5 This acid serves following functions: 1. Converts inactive pepsinogen and pro-rennin into active pepsin and rennin respectively. 2. Provides acidic medium for protein digestion. 3. Kills bacteria entered through food and prevents infection. 4. Prevents putrefaction of food in the stomach. A thick layer of mucus secreted by the mucus glands of the stomach prevent itself from the action of the gastric acid. Excess acid damages gastric mucosa and causes gastric and duodenal ulcers.

Salivary Glands

Salivary glands are the exocrine glands that secrete saliva and through a system of ducts, it is poured into the mouth. In humans, three major pairs of salivary glands are present, parotid, submandibular and sublingual. In healthy individuals between 0.5 to 1.5 litres of saliva is produced per day. Saliva serves following functions in the oral cavity. 1. It lubricates and protects the soft and hard tissues of the oral cavity 2. It also gives protection from dental caries 3. Saliva prevents microbial growth in the oral cavity. 4. Saliva can encourage soft tissue repair by decreasing clotting time and increasing wound contraction 5. Saliva contains the enzyme amylase that hydrolyses starch into maltose and dextrin. Hence saliva allows digestion to occur before the food reaches the stomach 6. Saliva acts as a solvent in which solid particles can dissolve in and enter the taste buds located on the tongue.

Salivary glands in Human(Diagramm)

Heterotrophic Nutrition

 When an organism depends on others for food, such a mode of nutrition is called as a heterotrophic mode of nutrition. These organisms depend on autotrophs for their nutritional requirements. E.g. Animals which eat plants as their food are called herbivores. Animals which eat other animals as their food are called carnivores. Holozoic, saprophytic and parasitic nutrition are all types of heterotrophic nutrition.

 

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Glandular Epithelium

Many small glands present in the inner layer of stomach and intestine take part in the digestion of food. These glands are present in the epithelial lining of stomach and intestine.  The glands present in different regions of the stomach are called as gastric glands. They are responsible for the secretion of mucus, hydrochloric acid and enzymes like pepsinogen. The glands present in the epithelial lining of the small intestine and large intestine are called as intestinal glands. Glands of the small intestine are responsible for the secretion of intestinal juice also called as succus entericus. Intestinal juice contains hormones, digestive enzymes, alkaline mucus, substances to neutralize hydrochloric acid coming from the stomach. Intestinal juice completes the digestion started by pancreatic juice. Glands of the large intestine are associated with absorption of water and electrolytes

Villi and Micro Villi

Complete digestion and absorption of food take place in the small intestine. Pancreatic juice coming from the pancreas, bile from the liver and intestinal juice secreted by the intestinal glands complete the digestion of food material. All the digested nutrients are absorbed by the long finger-like projections present in the ileum of the small intestine. These small finger-like projections of the inner wall of intestine are called as villi (singular: villus). Each villus has its cell membrane of the lumen side again folded into microscopic processes, called microvilli. Villi increase the internal surface area of the intestinal walls making available a greater surface area for absorption. Digested nutrients pass into the semipermeable villi through diffusion. Villi also help in chemical digestion of food by secreting digestive enzymes. Villi and microvilli of the small intestine

 

 

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Liver

The liver is the largest and major digestive gland of humans Liver, in humans, is located in the upper right-hand portion of the abdomen. This organ is dark reddish brown in colour due to an extensive blood supply. Some of the important functions of the liver are as follows: 1. It secretes bile that helps in digestion. 2. It filters the blood coming from digestive tract before passing it to the rest of the body. 3. It detoxifies various metabolites and drugs 4. The liver makes proteins important for blood clotting and other functions. 5. It stores and releases glucose as needed. 6. It processes haemoglobin, from the dead and worn out RBCs, for the iron content (the liver stores iron). 7. Conversion of harmful ammonia to urea takes place in the liver.

Digestive Juices

Pancreatic juice, bile and intestinal juice (succus entericus) are collectively called as digestive juices. A common duct from digestive glands pours the secretions into the duodenum. Chyme enters into the small intestine where complete digestion takes place due to the action of various enzymes. In the duodenum, the acidity of chyme is turned to alkalinity by the action of bile coming from the liver. This is necessary for pancreatic enzyme action. Bile also emulsifies the fats into smaller globules. Pancreatic and intestinal amylases break down the carbohydrates into glucose. Trypsin and chymotrypsin are the proteases responsible for the breakdown of proteins finally into amino acids. Lipase is the enzyme which acts on the emulsified fats and breaks them down into glycerol and fatty acids.

Water Absorption in Large Intestine

 The large intestine is not involved in digestion of food or absorption of nutrients. The major function of the large intestine is to absorb water from the remaining indigestible food matter and make the stool solid. The large intestine also helps in absorption of vitamins made by bacteria that normally live in the large intestine. The innermost layer of the large intestine also acts as a barrier and protects from microbial infections and invasions. Rectum stores the undigested food temporarily until defaecation.

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Respiration

 Introduction to Respiration

 Respiration broadly means the exchange of gases.  Animals and plants have different means of exchange of gases. At a cellular level, respiration means the burning of the food at the for generating the energy needed for other life processes. Cellular respiration may take place in the presence or absence of oxygen.

A General Reaction of Respiration(Diagramm)

Respiration in Humans

The human respiratory system is more complex and involves breathing, exchange of gases and cellular respiration. A well defined respiratory system helps breathing and exchange of gases. Breathing involves inhalation of oxygen and exhalation of carbon dioxide. The gaseous exchange takes place in the lungs and oxygen is supplied to all cells of the body. Cellular respiration takes place in each and every cell.

Respiratory System

The human respiratory system involves the nose, nasal cavities, pharynx, larynx, trachea/windpipe, bronchi, bronchioles and alveoli. Bronchioles and alveoli are enclosed in a pair of lungs. Rib cage, muscles associated with the rib cage and diaphragm, all help in inhalation and exhalation of gases. Exchange of gases takes place between an alveolar surface and surrounding blood vessels. Alveoli provide a large surface area for exchange of gases.

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Physiology of Respiration

 Breathing in humans is facilitated by the action of internal intercostal and external intercostal muscles attached to the ribs and the diaphragm. When the dome-shaped diaphragm contracts and becomes flattened and the rib cage is expanded due to the action of intercostal muscles, the volume of the lungs increases, pressure there drops down and the air from outside gushes in. This is inhalation. To exhale, the diaphragm relaxes, becomes dome-shaped again, chest cavity contracts due to the action of intercostal muscles, the volume inside the lungs decreases, pressure increases and the air is forced out of the lungs. Inhaled air increases the concentration of oxygen in the alveoli,  so oxygen simply diffuses into the surrounding blood vessels. Blood coming from cells has more concentration of carbon dioxide than outside air and thus carbon dioxide simply diffuses out of the blood vessels into the alveoli. Thus, breathing takes place due to the combined action of intercostal muscles and diaphragm while the exchange of gases takes place due to simple diffusion.

 Breathing Mechanism in Human(Diagramm)

Inhalation and Exhalation

 The process of taking in air rich in oxygen is called inhalation. Similarly, the process of giving out air rich in carbon dioxide is called exhalation. One breath comprises one inhalation and one exhalation. A person breathes several times in a day. The number of times a person breathes in one minute is termed as his/her breathing rate.

Diffusion

 Diffusion is the movement of molecules from high concentration area to the low concentration area without spending any enrgy.

Diffusion of gas molecules(Diagramm)

Cellular Respiration

 Cellular respiration is set of metabolic reactions occurring inside the cells to convert biochemical energy obtained from the food into a chemical compound called adenosine triphosphate (ATP).  Metabolism refers to a set of chemical reactions carried out for maintaining the living state of the cells in an organism.

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These can be divided into two categories: Catabolism – the process of breaking molecules to obtain energy. Anabolism – the process of synthesizing all compounds required by the cells. Therefore, respiration is a catabolic process, which breaks large molecules into smaller ones, releasing energy to fuel the cellular activities. Glycolysis, Krebs cycle and electron transport chain are the important processes of the cellular respiration.

Interlinking of Breathing and Cellular Respiration(Diagramm)

Aerobic Respiration

Aerobic respiration is a process in which the food i.e. glucose is converted into energy in the presence of oxygen. The general equation of aerobic respiration as a whole is as given below

Glucose + oxygen ⇒Carbon-dioxide + Water + Energy

This type of respiration takes place in animals, plants and other living organisms.

Respiration in Lower Animals

Lower animals lack a sophisticated respiratory system like lungs, alveoli etc. Respiration in them takes place by simple exchange mechanisms. Animals like earthworms take in gases through their skin. Fishes have gills for gaseous exchange. Insects have a tracheal system, which is a network of tubes, through which air circulates and gaseous exchange takes place. Frogs breathe through their skin when in water and through their lungs when on land.

Respiration in Muscles

Respiration in muscles can be anaerobic when there is not enough oxygen. Glucose gets broken down to carbon dioxide and lactic acid. This results in the accumulation of lactic acid that makes the muscles sore. This type of anaerobic respiration is also known as lactic acid fermentation

ATP

 It is the energy currency of the cell. ATP stands for Adenosine Tri-Phosphate. This molecule is created as a result reaction like photosynthesis, respiration etc. The three phosphate bonds present in the molecule are high energy bonds and when they are broken, a large amount of energy is released. Such released energy is then used for other metabolic reactions. Structure of ATP(Diagramm)

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Respiration in Plants

Unlike animals and humans, plants do not have any specialized structures for gaseous exchange They have stomata (present in leaves) and lenticels (present in stems) which are involved in the exchange of gases.  Compared to animals, plant roots, stems, and leaves respire at a very lower rate.

Transpiration

Transpiration is a biological process in which water is lost in the form of water vapour from the aerial parts of the plants. This process occurs mainly through the stomata where the exchange of gases (oxygen and carbon dioxide) occurs.  Transpiration helps in transportation of water from roots to upper parts of plants and this is explained by 'transpirational pull theory'. Loss of water, especially from leaves, acts as straw effect and pulls water upwards from roots. Transpiration also acts as an excretoy mechanism in plants as it helps to get rid of excess water

Why Do We Need Lungs

In unicellular organisms like an amoeba exchange of gases takes place through a general body surface by osmosis. In lower animals like an earthworm, the gaseous exchange takes place through their moist skin. The requirement of oxygen is sufficiently met by these ways. But as the animal starts becoming more and more complex, for example, human, the requirement of oxygen cannot be met alone by diffusion. Moreover, diffusion will not be able to supply oxygen to the deep-seated cells. This difficulty has led to the evolution of a more complex mechanism of gaseous exchange and that is the development of lungs. The alveoli present in the lungs provide large surface area required for the necessary gas exchange.

Transportation in Human Beings

 Transportation

 All living organisms need few necessary components like air, water, and food for their survival. On our regular basis, animals ensure these elements by breathing, drinking and eating. The required elements are transported to their body cells and tissues by a  transportation system. In plants, vascular tissue is responsible for transporting the substances.

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Transportation in Humans

Transportation in humans is done by the circulatory system. The circulatory system in humans mainly consists of blood, blood vessels and heart. It is responsible for the supply of oxygen, nutrients, removal of carbon dioxide and other excretory products. It also helps to fight the infections.

Heart

The muscular organ which is located near the chest slightly towards the left in the thoracic region. The heart is the main pumping organ of the body. The human heart is divided into four chambers which are involved in the transportation of oxygenated and deoxygenated blood. The upper two chambers are called as atria whereas the lower two chambers are called as ventricles. Human Heart(Diagramm)

Blood Vessels

Blood vessels carry blood throughout the body. There three types of blood vessels; arteries, veins and blood capillaries. Arteries carry oxygenated blood and veins carry deoxygenated blood. Gaseous exchange takes place between blood and cells at capillaries.

Difference between Arteries and Veins                    

            Arteries                                                                                Veins

1 An artery carries blood away from heart               A vein carries blood towards the heart

2 An artery is thicker than a vein                                   A vein is comparitively thinner

3 The Pulmonary artery carries                                     The pulmonary vein carries  deoxygenated blood oxygenated blood

4 Arteries have rigid walls                                               Veins have comparitively thinner walls

5 Blood flows under pressure through an artery     Blood flow through vein is much calmer

6 Lumen of arteries is narrow                                       Lumen of veins is comparitively wider

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Class 10 Science Notes Chapter 7 Control and Coordination: 

.The Nervous System

Movement in organisms

The ability of organisms to move certain body parts is movement.

When they move from one place to another, it is called locomotion.

Organisms show movements in response to stimuli.

Introduction to control & coordination

• Organisms move in response to various kinds of stimuli like light, heat, nutrients/food, etc.
• All the activities in animals are controlled and coordinated by the nervous and endocrine system.
• Hormones are chemical messengers, which assist the nervous system in carrying out various functions. They are secreted by endocrine glands.
• Hormones in plants coordinate the movements.

THE NERVOUS SYSTEM

Neuron

Neuron is the structural and functional unit of the nervous system.

• Each neuron has three main parts: dendrites, cyton/soma/cell body and axon.
• Dendrites receive impulses from other neurons.
• Cyton/soma processes the impulse.
• Axon transmits the impulse, either to another neuron or to muscles/glands, etc.
• Axon may be myelinated or non-myelinated.
• The impulse transmission is faster in myelinated neurons.

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Central nervous system

The central nervous system (CNS) is made up of the brain and the spinal cord. Functions of different parts of the brain are:

• Cerebrum is responsible for reasoning, logic, emotions, speech, memory, visual processing, recognition of auditory and taste stimuli, etc.
• Cerebellum regulates and coordinates body movements, posture and balance.
• Pons relays signals from hindbrain to forebrain.
• Medulla Oblongata controls all involuntary movements like vomiting, sneezing, yawning, heartbeat, breathing, blood pressure, etc.
• Medulla oblongata continues as the spinal cord which runs through the vertebral column and it controls reflex actions.

Peripheral nervous system

• The nerves given out by the brain and the spinal cord form the peripheral nervous system (PNS).
• There are 12 cranial nerves and 31 spinal nerves in humans.

Somatic nervous system

• It forms a part of the PNS.
• The nerves of PNS that control the voluntary actions of the body form the somatic nervous system.

Autonomic nervous system

• All the nerves of the PNS that control the involuntary actions in the body form the autonomic nervous system.
•  

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• Two divisions of autonomic nervous system are: sympathetic and parasympathetic nervous system.
• The sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response, while the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.

Reflex action

Reflex action is a sudden, involuntary reaction of the body in response to stimuli.

Reflex arc

• It is the path followed by electrical impulse during a reflex action.
• The impulse travels from the receptor organ to the spinal cord/brain. It is processed there and the information is brought back to the concerned muscle to carry out the action.
• Thus, receptor organ, sensory/afferent neuron, interneuron, motor/efferent neuron and effector organ are the components of a reflex arc.

Protection of CNS

The brain is protected by 3 main layers –

• The bony skull (cranium)
• The cerebrospinal fluid
• The meninges (Dura mater, Arachnoid and Pia mater).

Plant Hormones and Movements

Plant hormones

Control and coordination in plants are carried out by hormones.

Plant Hormone	Function
Auxin	Helps in Growth of Plant Tissue
Cytokinin	Promotes Cell division, delays aging of cells
Gibberilins	Helps in growth of stems, initiates seed germination, promotes flowering, cell division and seed growth after germination
Abscisic acid	Inhibits growth and causes wilting of leaves, promotes dormancy of buds and seeds
Ethylene	This is a gaseous hormone which causes ripening of fruits

Growth independent movements

The movements which are not growth related are called nastic movements. These movements occur in response to environmental stimuli but the direction of response is not dependent on the direction of the stimulus.

• The movement in the touch-me-not plant is thigmonastic movement (movement in response to touch).

Growth-related movements in plants

The movements which are growth related are called tropic movements. These movements occur in response to environmental stimuli and the direction of the response is dependent on the direction of the stimulus.

Examples:

• Phototropic movement (light dependent)
• Geotropic movement (gravity dependent)
• Chemotropic movement (chemical dependent)
• Hydrotropic movement (water dependent)
• Thigmotropic movement (touch dependent)

Geotropism

Movement of plant parts in response to earth’s gravitational force is known as geotropism/gravitropism.

• Towards gravity – positive geotropism
• Away from gravity – negative geotropism
• Root grows towards gravity and shoot grows away from gravity

Phototropism

Movement of plant parts in response to light is known as phototropism.

• Towards light – positive phototropism
• Away from light – negative phototropism
• Stems move towards light and roots move away from light

\

Hydrotropism

Movement of plant parts in response to water or moisture.

• Towards water – positive hydrotropism
• Away from water – negative hydrotropism
• Again, root movement in search of water is positive hydrotropism

Chemotropism

Movement of plant parts in response to chemical stimuli is known as chemotropism.

• Towards chemical – positive chemotropism
• Away from chemical – negative chemotropism
• The growth of pollen tube towards the ovule is positive chemotropism

Thigmotropism

Movement of plant parts in response to touch is called as thigmotropism.

• Towards touch – Positive thigmotropism
• Away from touch – negative thigmotropism
• Movement of tendrils around the support is positive thigmotropism

The Endocrine System

Exocrine glands

Exocrine glands are glands that discharge secretions by means of  ducts, which open onto an epithelial surface.

 

Endocrine glands

Endocrine glands are the ductless glands which secrete hormones into the bloodstream in humans.

Pituitary gland

• It is a pea-sized gland located at the base of the brain.
• It is the master gland as it controls the secretions of all the other endocrine glands.
• It also secretes Growth Hormone (GH). Under-secretion of GH causes ‘Dwarfism’ and over-secretion causes ‘Gigantism’ in children and ‘Acromegaly’ in adults.

Thyroid gland

• It is a butterfly-shaped gland located in the throat.
• It secretes the hormone ‘Thyroxine’ which regulates the metabolism of the body.
• Iodine is required to synthesize thyroxine in the body.
• In case of iodine deficiency, under-secretion of thyroxine leads to goitre.

Pancreas

• It is a leaf-like gland present behind the stomach in the abdomen.
• It is an endocrine as well an exocrine gland.
• As an endocrine gland, it manufactures two hormones – Insulin and glucagon. Both these hormones act antagonistically and regulate the sugar level in the blood.
• As an exocrine gland, it secretes enzymes to break down the proteins, lipids, carbohydrates and nucleic acids in food.
• Insufficient amount of insulin from pancreas leads to diabetes.

Adrenal gland

• Occurs in pair above each kidney.
• It decreases in size with age.
• Secrets the hormone adrenaline which helps in flight and fight response.
• Also secretes nor adrenaline

Gonads

• Gonads are the gamete-producing organs – testes in males and ovaries in females.
• The testes produce the male hormone testosterone and ovaries produce the female hormones oestrogen and progesterone.
• Testosterone and oestrogen help in producing gametes and are responsible for the sexual characteristics in males and females respectively.
• Progesterone is the pregnancy hormone..

Other endocrine organs

• The other endocrine organs include the hypothalamus, parathyroid, pineal and thymus glands.

Frequently asked Questions on CBSE Class 10 Science Notes Chapter 7: Control and Coordination

What is the function of the Central nervous system?

The central nervous system (CNS) controls most functions of the body and mind. It consists of two parts: the brain and the spinal cord. The brain is the center of our thoughts, the interpreter of our external environment, and the origin of control over body movement.

What are some facts about the human brain?

1. 60% of the human brain is composed of fat 2. Brain contains about 100 billion neurons and 100 trillion connection 3. The texture of brain is siilar to that of firm jelly

How many parts does the human eye have?

The human eye totally consists of 7 parts that work together.