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Maths NCERT solution class 10 chapter 3 Pairs of linear equations in two variables

Maths NCERT solution class 10 chapter 3 Pairs of linear equations in two variables

  • Exercise 3.1
  • Exercise 3.2
  • Exercise 3.3
  • Exercise 3.4
  • Exercise 3.5
  • Exercise 3.6

Maths NCERT solution class 10 chapter 4 quadratic equations: view

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Maths NCERT solution class 10 chapter 1 Real Numbers

Maths NCERT solution class 10 chapter 1 Real Numbers in this chapter.

All proofs need to be given in a non-didactic manner, allowing the learner to see the flow of reason by maths NCERT solution class 10 for real numbers. The focus should be on proofs where a short and clear argument reinforces mathematical thinking and reasoning. Whenever possible, more than one proof is to be given by maths ncert solution. Proofs and solutions need to be used as vehicles for helping the learner develop a clear and logical way of expressing her arguments. All geometric constructions should be accompanied by an analysis of the construction and a proof for the steps taken to do the required construction. Accordingly, the children would be trained to do the same while doing constructions.

Maths NCERT solution class 10 chapter 1 Real Numbers

  1. Exercise 1.1
  2. Exercise 1.2
  3. Exercise 1.3
  4. Exercise 1.4

Motivational Stories: Read here

The matter needs to be linked to what the child has studied before, and to Her experiences. The language used in the post, including that for ‘word problems’, must be Clear, simple and unambiguous. Concepts/processes should be introduced through situations from the Children’s environment.

For each concept/process give several examples and exercises, but not of The same kind. This ensures that the children use the concept/process again And again, but in varying contexts. Here ‘several’ should be within reason, Not overloading the child. Encourage the children to see, and come out with, diverse solutions to Problems. As far as possible, give the children motivation for results used

Maths NCERT solution class 10 chapter 2 polynomials: view

Chemistry: chemical reactions and equations Class 10 chapter 1

Chemical Reactions and Equations: Chapter 01 Class 10 Chemistry

Contents:Chemical Reactions and Equations: Chapter 01 Class 10 Chemistry

  1. Chemical Reactions and Equations: Chapter 01 Class 10 Chemistry. Chemical Reactions Involve Chemical Changes Formation of New Substances by the Rearrangement of Atoms Reactants and Products.
  2. Characteristics of Chemical Reactions: Evolution of a Gas, Formation of a Precipitate, Change in Colour, Change in Temperature and Change in State.
  3. Chemical Equations : Short-Hand Method of Representing a Chemical Reaction.
  4. Balanced Chemical Equations and Unbalanced Chemical Equations.
  5. Balancing of Chemical Equations to Satisfy the Law of Conservation of Mass in Chemical Reactions.
  6. To Make Chemical Equations More Informative : By Indicating the Physical States of Reactants and Products in the Equation (Solid, Liquid, Aqueous Solution and Gas), By Indicating the Heat Changes in the Equation (Exothermic Reactions and Endothermic Reactions), and by Indicating the Conditions Under Which the Reaction Takes Place (Heat, Catalyst, Pressure and Temperature).
  7. Important Examples on Writing of Balanced Chemical Equations.
  8. Types of Chemical Reactions : Combination Reactions, Decomposition Reactions, Displacement Reactions, Double Displacement Reactions, and, Oxidation and Reduction Reactions, Oxidising Agents and Reducing Agents.
  9. Uses of Decomposition Reactions: Decomposition Reactions in Our Body, Effects of Oxidation Reactions in Everyday Life, Corrosion of Metals and Rancidity of Food, Prevention of Rancidity of Food : Adding Anti-Oxidants, Packaging in Nitrogen Gas, Keeping in a Refrigerator, Storing in Air-Tight Containers, and Away From Light.
Chemical reactions and equations

Chemical Reactions and Equations: Chapter 01 Class 10 Chemistry

Chemical reactions are the processes in which new substances with new properties are formed. During a chemical reaction, atoms of one element do not change into those of another element. Only a rearrangement of atoms takes place in a chemical reaction.

  • (i) The substances which take part in a chemical reaction are called reactants.
  • (ii) The new substances produced as a result of chemical reaction are called products.

The burning of magnesium in air to form magnesium oxide is an example of a chemical reaction.

  • before burning in air, the magnesium ribbon is cleaned by rubbing with a sand paper. This is done to remove the protective layer of magnesium oxide from the surface of magnesium ribbon .

Some daily life example of chemical reactions

  • Souring of milk (when left at room temperature during summer).
  • Formation of curd from milk, Cooking of food, Digestion of food in our body.
  • Process of respiration.
  • Fermentation of grapes.
  • Rusting of iron (when left exposed to humid atmosphere).
  • Burning of fuels (like wood, coal, kerosene, petrol and LPG).
  • Burning of candle wax.
  • Ripening of fruits are all chemical changes which involve chemical reactions.

Characteristics of Chemical Reactions

  • In a chemical reaction, the substances known as reactants are converted into new substances called products. The conversion of reactants into products in a chemical reaction is often accompanied by some features which can be observed easily. The easily observable features (or changes) which take place as a result of chemical reactions are known as characteristics of chemical reactions. The important characteristics of chemical reactions are :
  • (i) Evolution of a gas
  • (ii) Formation of a precipitate
  • (iii) Change in colour
  • (iv) Change in temperature, and
  • (v) Change in state

1. Evolution of a Gas

  • Some chemical reactions are characterised by the evolution of a gas.
  • the chemical reaction between zinc and dilute sulphuric acid is characterised by the evolution of hydrogen gas
  • chemical reaction between sodium carbonate and dilute hydrochloric acid is characterised by the evolution of carbon dioxide gas.
Evaluation of gas

2. Formation of a Precipitate

  • Some chemical reactions are characterised by the formation of a precipitate.
  • The chemical reaction in which the solid substance is deposited in the base of a container is called a precipitation
  • the chemical reaction between potassium iodide and lead nitrate is characterised by the formation of a yellow precipitate of lead iodide.
  • the chemical reaction between sulphuric acid and barium chloride solution is characterised by the formation of a white precipitate of barium sulphate.

3. Change in Colour

  • Some chemical reactions are characterised by a change in colour.
  • the chemical reaction between citric acid and purple coloured potassium permanganate solution is characterised by a change in colour from purple to colourless.
  • the chemical reaction between sulphur dioxide gas and acidified potassium dichromate solution is characterised by a change in colour from orange to green.

4. Change in Temperature

  • Some chemical reactions are characterised by a change in temperature
  • the chemical reaction between quicklime and water to form slaked lime is characterised by a change in temperature (which is rise in temperature).
  • the chemical reaction between zinc granules and dilute sulphuric acid is also characterised by a change in temperature (which is rise in temperature).
  • the chemical reaction between barium hydroxide and ammonium chloride to form barium chloride, ammonia and water is characterised by a change in temperature (which is fall in temperature).
  • So there are two type of reactions when temperature changes occurred.

Exothermic Reactions: heat producing reactions

Endothermic Reactions: heat absorbing reaction

5. Change in State

  • Some chemical reactions are characterised by a change in state.
  • the combustion reaction of candle wax is characterised by a change in state from solid to liquid and gas (because wax is a solid, water formed by the combustion of wax is a liquid at room temperature whereas carbon dioxide produced by the combustion of wax is a gas).
  • There are some chemical reactions which can show more than one characteristics.
  • For example, the chemical reaction between zinc granules and dilute sulphuric acid shows two characteristics : evolution of a gas (hydrogen gas) and change in temperature (rise in temperature). Similarly, the chemical reaction between potassium iodide solution and lead nitrate solution shows two characteristics : formation of a precipitate (lead iodide precipitate) and change in colour (from colourless to yellow).

Chemical Reactions and Equations: Chapter 01 Class 10 Chemistry

CHEMICAL EQUATIONS

  • The method of representing a chemical reaction with the help of symbols and formulae of the substances involved in it is known as a chemical equation.

The substances which combine or react are known as reactants

The new substances produced in a reaction are known as products

chemical equation is a short-hand method of representing a chemical reaction.

Balanced and Unbalanced Chemical Equations

  1. A balanced chemical equation has an equal number of atoms of different elements in the reactants and products. a balanced chemical equation has equal masses of various elements in reactants and products
  2. An unbalanced chemical equation has an unequal number of atoms of one or more elements in the reactants and products. an unbalanced equation has unequal masses of various elements in reactants and products.

the law of conservation of mass, “matter can neither be created nor destroyed in a chemical reaction”.

To Make Equations More Informative

The chemical equations can be made more informative in three ways :

  1. By indicating the “physical states” of the reactants and products.
  2. By indicating the “heat changes” taking place in the reaction.
  3. By indicating the “conditions” under which the reaction takes place.

1. To Indicate the Physical States of Reactants and Products in an Equation

  • Solid state is indicated by the symbol (s)
  • Liquid state is indicated by the symbol (l)
  • Aqueous solution (solution made in water) is indicated by the symbol (aq)
  • Gaseous state is indicated by the symbol (g)

2. To Indicate the Heat Changes in an Equation.

There are two types of reactions on the basis of heat changes involved : exothermic reactions and endothermic reactions.

Those reactions in which heat is evolved are known as exothermic reactions

Those reactions in which heat is absorbed are known as endothermic reactions.

3. To Indicate the Conditions Under Which the Reaction Takes Place.

If heat is required for a reaction to take place, then the heat sign delta (∆) is put over the arrow of the equation. If the reaction takes place in the presence of a catalyst, then the symbol or formula of the catalyst is also written above or below the arrow sign in the equation.

TYPES OF CHEMICAL REACTIONS

important types of chemical reactions are :

  • 1. Combination reactions,
  • 2. Decomposition reactions,
  • 3. Displacement reactions,
  • 4. Double displacement reactions, and
  • 5. Oxidation and Reduction reactions.

1. COMBINATION REACTIONS

  • Those reactions in which two or more substances combine to form a single substance, are called combination reactions.

2. DECOMPOSITION REACTIONS

  • Those reactions in which a compound splits up into two or more simpler substances are known as decomposition reactions. a decomposition reaction is just the opposite of a combination reaction.

When a decomposition reaction is carried out by heating, it is called ‘thermal decomposition’.

3. DISPLACEMENT REACTIONS

  • Those reactions in which one element takes the place of another element in a compound, are known as displacement reactions. more reactive element displaces a less reactive element from its compound.

4. DOUBLE DISPLACEMENT REACTIONS

  • Those reactions in which two compounds react by an exchange of ions to form two new compounds are called double displacement reactions.

5. OXIDATION AND REDUCTION REACTIONS (REDOX Reactions)

Oxidation :

  1. (i) The addition of oxygen to a substance is called oxidation.
  2. (ii) The removal of hydrogen from a substance is also called oxidation.

Reduction :

  • (i) The addition of hydrogen to a substance is called reduction.
  • (ii) The removal of oxygen from a substance is also called reduction.

the process of reduction is just the opposite of oxidation. Moreover, oxidation and reduction occur together

Oxidising agent :

  • (i) The substance which gives oxygen for oxidation is called an oxidising agent.
  • (ii) The substance which removes hydrogen is also called an oxidising agent.

Reducing agent :

  • (i) The substance which gives hydrogen for reduction is called a reducing agent.
  • (ii) The substance which removes oxygen is also called a reducing agent. The oxidation and reduction reactions are also called redox reactions

There is another concept of oxidation and reduction in terms of metals and non-metals.

  • (i) The addition of non-metallic element (or removal of metallic element) is called oxidation.
  • (ii) The addition of metallic element (or removal of non-metallic element) is called reduction.

EFFECTS OF OXIDATION REACTIONS IN EVERYDAY LIFE

  • there are two common effects of oxidation reactions which we observe in daily life. These are :
  • 1. Corrosion of metals , and
  • 2. Rancidity of food.

Corrosion

  • Corrosion is the process in which metals are eaten up gradually by the action of air, moisture or a chemical (such as an acid) on their surface. Corrosion is caused mainly by the oxidation of metals by the oxygen of air. Rusting of iron metal is the most common form of corrosion.

Rancidity

  • The condition produced by aerial oxidation of fats and oils in foods marked by unpleasant smell and taste is called rancidity.

1. Rancidity can be prevented by adding anti-oxidants to foods containing fats and oils

2. Rancidity can be prevented by packaging fat and oil containing foods in nitrogen gas

3. Rancidity can be retarded by keeping food in a refrigerator

4. Rancidity can be retarded by storing food in air-tight containers.

5. Rancidity can be retarded by storing foods away from light.

NCERT Solution

Chemical Reactions and Equations: Chapter 01 Class 10 Chemistry

Page No 6:

Question 1:

Why should a magnesium ribbon be cleaned before it is burnt in air?

ANSWER:

Magnesium is an extremely reactive metal. When stored, it reacts with oxygen to form a layer of magnesium oxide on its surface. This layer of magnesium oxide is quite stable and prevents further reaction of magnesium with oxygen. The magnesium ribbon is cleaned by sand paper for removing this layer so that the underlying metal can be exposed to air.

Page No 6:

Question 2:

Write the balanced equation for the following chemical reactions.

  • (i) Hydrogen + Chlorine → Hydrogen chloride
  • (ii) Barium chloride + Aluminium sulphate → Barium sulphate +Aluminium chloride
  • (iii) Sodium + Water → Sodium hydroxide + Hydrogen

ANSWER:

  • (i) H2 (g) + Cl2 (g) → 2HCl (g)
  • (ii) 3BaCl2 (s) + Al2(SO4)3 (s) → 3BaSO4 (s) + 2AlCl3 (s)
  • (iii) 2Na(s) + 2H2O (l) → 2NaOH (aq) + H2 (g)

Page No 6:

Question 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 the solution of sodium chloride.
  • (ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.

ANSWER:

  • (i) BaCl2 (aq) + Na2SO4 (aq) → BaSO4(s) + 2NaCl (aq)
  • (ii) NaOH (aq) + HCl (aq) → NaCl (aq) + H2O (l)

Page No 10:

Question 1:

A solution of a substance ‘X’ is used for white washing.

  • (i) Name the substance ‘X’ and write its formula.
  • (ii) Write the reaction of the substance ‘X’ named in (i) above with water.

ANSWER:

(i) The substance ‘X’ is calcium oxide. Its chemical formula is CaO.

(ii) Calcium oxide reacts vigorously with water to form calcium hydroxide (slaked lime).

Page No 10:

Question 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.

ANSWER:

Water (H2O) contains two parts hydrogen and one part oxygen. Therefore, the amount of hydrogen and oxygen produced during electrolysis of water is in a 2:1 ratio. During electrolysis, since hydrogen goes to one test tube and oxygen goes to another, the amount of gas collected in one of the test tubes is double of the amount collected in the other.

Page No 13:

Question 1:

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

ANSWER:

When an iron nail is placed in a copper sulphate solution, iron displaces copper from copper sulphate solution forming iron sulphate, which is green in colour.

Therefore, the blue colour of copper sulphate solution fades and green colour appears.

Page No 13:

Question 2:

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

ANSWER:

Sodium carbonate reacts with calcium chloride to form calcium carbonate and sodium chloride.

In this reaction, sodium carbonate and calcium chloride exchange ions to form two new compounds. Hence, it is a double displacement reaction.

Page No 13

Question 3:

Identify the substances that are oxidised and the substances that are reduced in the following reactions.

(i) 4Na (s) + O2 (g) → 2Na2O (s)
(ii) CuO (s) + H2 (g) → Cu (s) + H2O (l)

ANSWER:

(i) Sodium (Na) is oxidised as it gains oxygen and oxygen gets reduced.

(ii) Copper oxide (CuO) is reduced to copper (Cu) while hydrogen (H2) gets oxidised to water (H2O).

Chemical Reactions and Equations: Chapter 01 Class 10 Chemistry

Page No 14

Question 1

Which of the statements about the reaction below are incorrect?

(i) (a) and (b)

  • (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

ANSWER:

(i)(a) and (b)

Page No 14

Question 2:

The above reaction is an example of a

  1. (a) combination reaction.
  2. (b) double displacement reaction.
  3. (c) decomposition reaction.
  4. (d) displacement reaction.

ANSWER:

(d) The given reaction is an example of a displacement reaction.

Page No 15

Question 3:

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

  1. (a) Hydrogen gas and iron chloride are produced.
  2. (b) Chlorine gas and iron hydroxide are produced.
  3. (c) No reaction takes place.
  4. (d) Iron salt and water are produced.

ANSWER:

(a) Hydrogen gas and iron chloride are produced. The reaction is as follows:

Page No 15

Question 4:

What is a balanced chemical equation? Why should chemical equations be balanced?

ANSWER:

A reaction which has an equal number of atoms of all the elements on both sides of the chemical equation is called a balanced chemical equation.

The law of conservation of mass states that mass can neither be created nor destroyed. Hence, in a chemical reaction, the total mass of reactants should be equal to the total mass of the products. It means that the total number of atoms of each element should be equal on both sides of a chemical equation. Hence, it is for this reason that chemical equations should be balanced.

Page No 15

Question 5:

Translate the following statements into chemical equations and then balance them.

(a) Hydrogen gas combines with nitrogen to form ammonia.

(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.

(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.

(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

ANSWER:

(a) 3H2 (g) + N2 (g) → 2NH3 (g)
(b) 2H2S (g) + 3O2 (g) → 2H2O (l) + 2SO2 (g)
(c) 3BaCl2 (aq) + Al2(SO4)3 (aq) → 2AlCl3 (aq) + 3BaSO4 (s)
(d) 2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g)

Page No 15

Question 6

Balance the following chemical equations.

(i) HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O
(ii) NaOH + H2SO4 → Na2SO4 + H2O
(iii) NaCl + AgNO3 → AgCl + NaNO3
(iv) BaCl2 + H2SO4 → BaSO4 + HCl

ANSWER:

(i) 2HNO3 + Ca(OH)2 → Ca(NO3)2 + 2H2O
(ii) 2NaOH + H2SO4 → Na2SO4 + 2H2O
(iii) NaCl + AgNO3 → AgCl + NaNO3
(iv) BaCl2 + H2SO4 → BaSO4 + 2HCl

Page No 15

Question 7

Write the balanced chemical equations for the following reactions.

(a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water

(b) Zinc + Silver nitrate → Zinc nitrate + Silver

(c) Aluminium + Copper chloride → Aluminium chloride + Copper

(d) Barium chloride + Potassium sulphate → Barium sulphate +

Potassium chloride

ANSWER:

(a) Ca(OH)2 + CO2 → CaCO3 + H2O
(b) Zn + 2AgNO3 → Zn(NO3)2 + 2Ag
(c) 2Al + 3CuCl2 → 2AlCl3 + 3Cu
(d) BaCl2 + K2SO4 → BaSO4 + 2KCl

Page No 15

Question 8:

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

(a)Potassium bromide (aq) + Barium iodide (aq)­ → Potassium iodide (aq) +

Barium bromide(s)

(b) Zinc carbonate (s) → Zinc oxide (s) + Carbon dioxide (g)

(c) Hydrogen (g) + Chlorine (g) → Hydrogen chloride (g)

(d) Magnesium (s) + Hydrochloric acid (aq) → Magnesium chloride (aq) + Hydrogen (g)

ANSWER

(a) Double displacement reaction

(b) Decomposition reaction

(c) Combination reaction

(d) Displacement reaction

Page No 15

Question 9:

What does one mean by exothermic and endothermic reactions? Give examples.

ANSWER:

Chemical reactions that release energy in the form of heat, light, or sound are called exothermic reactions.

Example: Mixture of sodium and chlorine to yield table salt

In other words, combination reactions are exothermic.

Reactions that absorb energy or require energy in order to proceed are called endothermic reactions.

For example: In the process of photosynthesis, plants use the energy from the sun to convert carbon dioxide and water to glucose and oxygen.

Page No 15

Question 10:

Why is respiration considered an exothermic reaction? Explain.

ANSWER:

Energy is required to support life. Energy in our body is obtained from the food we eat. During digestion, large molecules of food are broken down into simpler substances such as glucose. Glucose combines with oxygen in the cells and provides energy. The special name of this combustion reaction is respiration. Since energy is released in the whole process, it is an exothermic process.

Page No 15

Question 11:

Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.

ANSWER:

Decomposition reactions are those in which a compound breaks down to form two or more substances. These reactions require a source of energy to proceed. Thus, they are the exact opposite of combination reactions in which two or more substances combine to give a new substance with the release of energy.

Decomposition reaction:

Combination reaction:

Page No 16

Question 12:

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

ANSWER:

(a) Thermal decomposition:

(b) Decomposition by light:

(c) Decomposition by electricity:

Page No 16

Question 13

What is the difference between displacement and double displacement reactions? Write equations for these reactions.

ANSWER:

In a displacement reaction, a more reactive element replaces a less reactive element from a compound.

where A is more reactive than B

In a double displacement reaction, two atoms or a group of atoms switch places to form new compounds.

For example:

Displacement reaction:

Double displacement reaction:

Page No 16

Question 14:

In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.

ANSWER:

2AgNO3 (aq) + Cu (s) → Cu(NO3)2 (aq) + 2Ag (s)
Silver Nitrate + Copper → Copper Nitrate + Silver

Page No 16

Question 15:

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

ANSWER:

A reaction in which an insoluble solid (called precipitate) is formed is called a precipitation reaction.

For example:

In this reaction, calcium carbonate is obtained as a precipitate. Hence, it is a precipitation reaction.

Another example of precipitation reaction is:

In this reaction, barium sulphate is obtained as a precipitate.

Page No 16

Question 16:

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

(a) Oxidation

(b) Reduction

ANSWER:

(a) Oxidation is the gain of oxygen.

For example:

(i)

(ii)

In equation (i), H2 is oxidized to H2O and in equation (ii), Cu is oxidised to CuO.

(b) Reduction is the loss of oxygen.

For example:

(i)

(ii)

In equation (i), CO2 is reduced to CO and in equation (ii), CuO is reduced to Cu.

Page No 16

Question 17:

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

ANSWER:


‘X’ is copper (Cu) and the black-coloured compound formed is copper oxide (CuO). The equation of the reaction involved on heating copper is given below.

Page No 16

Question 18

Why do we apply paint on iron articles?

ANSWER

Iron articles are painted because it prevents them from rusting. When painted, the contact of iron articles from moisture and air is cut off. Hence, rusting is prevented. So presence of air and moisture is essential for rusting to take place.

Page No 16

Question 19:

Oil and fat containing food items are flushed with nitrogen. Why?

ANSWER:

Nitrogen is an inert gas and does not easily react with these substances. On the other hand, oxygen reacts with food substances and makes them rancid. Thus, bags used in packing food items are flushed with nitrogen gas to remove oxygen inside the pack. When oxygen is not present inside the pack, rancidity of oil and fat containing food items is avoided.

Page No 16

Question 20:

Explain the following terms with one example each.

(a) Corrosion

(b) Rancidity

ANSWER

(a) Corrosion:

Corrosion is defined as a process where materials, usually metals, deteriorate as a result of a chemical reaction with air, moisture, chemicals, etc.

For example, iron, in the presence of moisture, reacts with oxygen to form hydrated iron oxide.

This hydrated iron oxide is rust.

(b) Rancidity:

The process of oxidation of fats and oils that can be easily noticed by the change in taste and smell is known as rancidity.

For example, the taste and smell of butter changes when kept for long.

Rancidity can be avoided by:

  • Storing food in air tight containers
  • Storing food in refrigerators
  • Adding antioxidants
  • Storing food in an environment of nitrogen

Chemical Reactions and Equations: Chapter 01 Class 10 Chemistry

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ACIDS, BASES AND SALTS: Chapter 02 Class 10 Chemistry

Science for Tenth Class 10 X standard Physics CCE pattern Part 1 CBSE NCERT Value Based Question Answers Lakhmir Singh Manjit Kaur S Chand pdf

Science for Tenth Class 10 X standard Biology CCE pattern Part 3 CBSE NCERT Value Based Question Answers Lakhmir Singh Manjit Kaur S Chand pdf

Science for Tenth Class 10 X standard Chemistry CCE pattern Part 2 CBSE NCERT Value Based Question Answers Lakhmir Singh Manjit Kaur S Chand pdf

Social and Political Life: Social Science class 6

CONTENTS

UNIT I DIVERSITY

Chapter 1 Understanding Diversity

Chapter 2 Diversity and Discrimination

UNIT II GOVERNMENT

Chapter 3 What is Government?

Chapter 4 Key Elements of a Democratic Government

UNIT III LOCAL GOVERNMENT AND ADMINISTRATION

Chapter 5 Panchayati Raj

Chapter 6 Rural Administration

Chapter 7 Urban Administration

UNIT IV LIVELIHOODS

Chapter 8 Rural Livelihoods

Chapter 9 Urban Livelihoods

SCIENCE TEXTBOOK FOR CLASS VI

CONTENTS

C H A P T E R    1 FOOD: WHERE DOES IT COME FROM? 1

C H A P T E R    2 COMPONENTS OF FOOD 8

C H A P T E R    3 FIBRE TO FABRIC 18

C H A P T E R    4 SORTING MATERIALS INTO GROUPS 26

C H A P T E R    5 SEPARATION OF SUBSTANCES 35

C H A P T E R    6 CHANGES AROUND US 46

C H A P T E R    7 GETTING TO KNOW PLANTS 52

C H A P T E R    8 BODY MOVEMENTS 66

C H A P T E R    9 THE LIVING ORGANISMS AND THEIR SURROUNDINGS 79

C H A P T E R    10 MOTION AND MEASUREMENT OF DISTANCES 95

C H A P T E R    11 LIGHT, SHADOWS AND REFLECTIONS 107

C H A P T E R    12 ELECTRICITY AND CIRCUITS 116

C H A P T E R    13 FUN WITH MAGNETS 125

C H A P T E R    14 WATER 136

C H A P T E R    15 AIR AROUND US

C H A P T E R    16 GARBAGE IN, GARBAGE OUT

OUR PASTS-I TEXTBOOK IN HISTORY FOR CLASS VI Social Science

1. WHAT, WHERE, HOW AND WHEN? 1

2. ON THE TRAIL OF THE EARLIEST PEOPLE 11

3. FROM GATHERING TO GROWING FOOD 22

4. IN THE EARLIEST CITIES 32

5. WHAT BOOKS AND BURIALS TELL US 43

6. KINGDOMS, KINGS AND AN EARLY REPUBLIC 54

7. NEW QUESTIONS AND IDEAS 65

8. ASHOKA, THE EMPEROR WHO GAVE UP WAR 75

9. VITAL VILLAGES, THRIVING TOWNS 87

10. TRADERS, KINGS AND PILGRIMS 99

11. NEW EMPIRES AND KINGDOMS 111

12. BUILDINGS, PAINTINGS AND BOOKS 122

Mathematics class 6

Contents

CHAPTER  1 KNOWING OUR NUMBERS

CHAPTER  2 WHOLE NUMBERS

CHAPTER  3 PLAYING WITH NUMBERS

CHAPTER  4 BASIC GEOMETRICAL IDEAS

CHAPTER  5 UNDERSTANDING ELEMENTARY SHAPES

CHAPTER  6 INTEGERS

CHAPTER  7 FRACTIONS

CHAPTER  8 DECIMALS

CHAPTER  9 DATA HANDLING

CHAPTER  10 MENSURATION

CHAPTER  11 ALGEBRA

CHAPTER  12 RATIO AND PROPORTION

CHAPTER  13 SYMMETRY

CHAPTER  14 PRACTICAL GEOMETRY

ANSWERS