Explore topic-wise InterviewSolutions in Current Affairs.

The National Commission of Rural Labour in its reports in 1990s found that uneven development and regional disparity triggered and accelerated seasonal migration.

(a) Hardening of cement

The correct answer is Man-made.

Seasonal migrants are not only poor but have little or no land at their native place.

(d) The ring changes its shape and the change cannot be reversed.

(d) expands first, then on cooling contracts and fits onto the wooden wheel.

Changes (i), (iii) and (iv) cannot be reversed, change (ii) can be reversed.

(d) mixing of salt in water is a change that can be reversed by evaporation.

The rural seasonal migrants work in agriculture and plantations, brick kilns, quarries, construction sites and fish processing.

In chemical changes, we get new substance.

Melting of wax in (c), which on cooling changes back to solid wax.

(i) Wax was melting. 

(iv) Melted wax was getting solidified. 

Decaying of plants is associated with slow change and chemical change.

Cold milk is heated and it becomes hot is a Reversible.

Yes, I observed many times.

A) Distress caused in rural areas

(a) Boiling 

(b) Water in the kettle gets converted into vapour 

(c) Endothermic 

(d) Water vapour converted into liquid (condensation)

Evaporation.

Yes, I can. It is a physical (reversible) change.

Service sector produce No goods

1. (c) 

2. (d) 

3. (a) 

4. (b)

No, we will find the crystals at the bottom of the beaker.

No get original substance by reversing the conditions.

When a solute is dissolved in a solvent, it forms a solution. 

Solute + solvent → solution

Yes. We get them through crystallization.

(a) I observe sugar solution is there. 

(b) The sugar is dissolved in the water.

(c) The sugar particle is mixed with water molecules. 

(d) The solute is sugar. 

(e) The solvent is water 

(f) Yes.

Changes which take place over a long period of time (hours/days/months/years) are known as slow changes.

1. Sugar is basically Sucrose. 

2. The molecular formula of Sugar is C₁₂ H₂₂ O₁₁ (or) C₁₂ (H₂O)₁₁ .

3. When sugar is heated, it loses all water molecules and decomposes to carbon. 

4. Chemical change; 

5. Irreversible change

Yes you seen large crystals of sugar (Missrf) or crystal salt.

Catalysts are substances that speed up the process of a chemical change and it will not undergo any change during the course of the reaction. For example, yeast acts as the catalyst in the fermentation of sugar.

A) a soluble solid from the solution.

1. Plastic decomposition 

2. Acid rains 

3. Global warming 

4. Oil spills in seas and rivers 

5. Earthquakes and 

6. Floods are some of the harmful physical and chemical changes in environment.

Nickel, platinum or palladium.

Physical and chemical changes occur all around us. These changes are essential parts of our daily lives. However a few of the physical and chemical changes that occur daily are harmful to the environment. For example 

1. Plastic decomposition, global warming, effects of acid rain and oil spills, earthquakes, floods etc. 

2. Plastic waste is a widely recognised source of pollution. Most plastics are nonbiodegradable. They take hundreds of years to decompose. Hence their disposal causes pollution. 

3. Global warming is due to drastic increase in the emission of carbon dioxide by the burning of fossil fuels. The climate change affects not only the atmosphere and living things on land but also creatures of ocean. 

4. Acidic gases are produced when fossil fuels such as coal and oil are burned in power station, factories and homes. 

5. Oil spills occur when liquid petroleum is released into the environment by human interference causing damage to creatures of ocean. 

6. Changes are quite common in nature. Human beings are misusing the natural re-sources for their needs. 

7. But we should take care that our needs should not bring drastic changes that causes harm to the nature and mankind.

A change can occurs in a substance by an alteration in the properties such as colour, texture and the state of the substance since there is formation of a new substance.

When water is added to soap powder we feel hot. When water is added to glucose we feel cold.

Explosion of a firework is a chemical change. This explosion produces heat,Tight, sound andampleasant gases that pollute the atmosphere.

When sugar is heated continuously then a black powdery substance is formed. This is a chemical change.

Correct option is D) all of these

Physical change: 

When the material undergoes a change in shape, size, colour or state, it is called a physical change. 

Eg: 

Heating ice, filling air into Balloons Chemical change: When a material undergoes a change in shape and size and a new material is formed, then we call it a chemical change. 

Eg: 

1. Burning of crackers 

2. Change of milk into curd 

3. Burning a piece of wood.

Physical contact of the substances, heat, light, electricity and pressure.

Physical changes: 

1. Chopping wood 

2. Mixing sand and water

3. Crushing a can

4. Mixtures of different coloured buttons

Chemical changes: 

1. Rusting of iron 

2. Digestion of food 

3. Boiling egg 

4. Rotting banana 

5. Burning of wood

The process of evaporation is not a good technique because the soluble impurites do not get removed in the process of evaporation.

Correct option is B) Chemica

The changes in which new substances with new chemical properties are formed are called chemical changes. 

Ex:- Reaction between washing soda and lemon juice in which CO₂ and other substance are formed.

1. I absolutely agree with this statement. 

2. It is because, when water is heated, water vapours are formed. Once water vapours are cooled water can be obtained again. 

1. Changes which are taken place by the involvement of human beings are called man made changes. 

2. Examples for man made changes are cooking of rice, construction of buildings, preparation of laddu.