Question

1. How is metal rim fixed on a wooden wheel of a cart? How is the changes made in that metal?
2. Write whether the following changes are reversible or irreversible. Give reasons. a) Drying the wet clothes.
b) Liquid water into water vapour.
c) Breaking a toy.
d)Melting of ice cream.
e)Preparing curd from milk
f)Changing shape of cloth by folding it.
3. We dissolve salt in water. How can we reverse this change?
4. Sam took out porridge kept in a glass bowl from the refrigerator. As he wanted it hot, he put out it directly into the microwave oven for heating. To his surprise the glass bowl cracked !! Can you help him figure out why this had happened?

Answer 1

The metal rim is first heated so that it can expand and then the wooden wheel is inserted in it. Then it is allowed to cool and the in contracts and fits tightly

A-physical
B-physical
C-chemical
D-physical
E-chemical
F-physical

We can reverse it by the process of evaporation
Because the glass was contracted as it was cold but because of sudden heating it expanded and broke

Answer 2

1. The metal rim is heated and fixed on the wheel as heating causes expansion. To make the metal rim firm, it is cooled as cooling causes contraction.