Important Question:

Que: Give two examples of irreversible changes.

Ans:

(a) Milk to cheese

(b) Cooking of food.

Que: Give two examples of slow changes.

Ans:

(i) Growing of plants

(ii) Ripening of fruits

Qur: Give one example of change in size.

Ans: Stretching of a spring.

Que: What changes the direction of a body?

Ans: Force.

Que: What kind of change is breaking of wood - reversible or irreversible?

Ans: Irreversible.

Que: Give an example of reversible change.

Ans: Melting is an example of reversible change.

Que: Growing of nails is an example of which type of change?

Ans: Slow change.   

Que: Name the process in which solid directly changes into vapour.

Ans: Sublimation.

Que: Water turns into which state when it becomes ice?

Ans: Solid state.

Que: Give an example of natural change.

Ans: Growth of a baby.

Que: Rusting of an iron is which type of change?

Ans: Irreversible change.

Que: When ice changes into water, which type of change occurs in it?

Ans: Change of state.

Que: Give an example of physical change.

Ans: Cooling of molten wax.

Que: Give an example of chemical change.

Ans: Burning of wax.

Que: What is change?

Ans: An alteration in the physical or chemical properties of a matter due to effect of some kind of energy is called change.

Que: What are the different forms of changes noticed?

Ans: The various type of changes noticed are:

1. Change in shape

2.Change in size

3. Change in colour

4. Change in state

5. Change in direction

Que: Define reversible change.

Ans.The changes in which it is possible to get back to the original product again is called reversible change.

Que: State the list of changes caused due to heating.

Ans: The changes caused due to heating are:

• Expansion
• Change in state
• Combustion

Que: What is chemical change?

Ans: The result which leads to the formation of new substance is called chemical change.

Que: What do you mean by combustion?

Ans: The property of a substance by which substance start burning on heating is called combustion.

Que: Define evaporation.

Ans: The process of conversion of liquids into its vapour state by heating is called evaporation.

Que: What do you mean by expansion?

Ans: Solids, liquids and gases occupy more space when they are heated. This is called expansion.

Que: Define fast changes with two examples.

Ans: The type of change which takes short time to complete is known as fast change. e.g.,

(i) Burning of forest.

(ii) Striking of a matchstick.

Que:List the characteristics of physical change?
Ans:

Following are the characteristics of physical change:

1. No new substances are formed.
2. Properties of a substance doesn’t change.
3. These changes are reversible.

Que:List the characteristics of chemical change?

Ans:

Following are the characteristics of chemical change:

1. Properties of products are different from reactants.
2. Most of the chemical changes are irreversible.
3. Loss or gain of energy occurs in a chemical change.

Que:Define melting?

Ans:The process by which solid substances melt and turn into liquid is known as melting.

Que:Define contraction?

Ans:It is the phenomenon in which a substance shrinks or changes its shape.

Que:Why the stretching of a rubber band is reversible change?

Ans:The stretching of a rubber band is a reversible change because after we leave the rubber, it gets back to its original position automatically.

Que:Why the burning of paper is an irreversible change?

Ans:
Burning of paper is an irreversible change because after burning, the paper, it is not possible to get back the same paper which was burnt.