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:
- No new substances are formed.
- Properties of a substance doesn’t change.
- These changes are reversible.
Que:List the characteristics of chemical change?
Ans:
Following are the characteristics of chemical change:
- Properties of products are different from reactants.
- Most of the chemical changes are irreversible.
- 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.
