V K Sally and S. K. Aggarwal Solutions for Chapter: Changes Around Us, Exercise 1: EXERCISES

Choose the correct words from the list given below :
List: solution, expands, irreversible, reversible. You may use a word/words more than once.

Distillation of petroleum to form petrol is a _____ change.

How does the solubility of a substance change with fall in temperature?

You have accidentally dropped a glass tumbler, which breaks. Is the change reversible? Give reason.

Give four examples of the change which cannot be reversed   

Give four examples of the change which can be reversed.

A thick coating of plaster of Paris paste is applied on a bandage on a fractured bone. The paste becomes hard on drying. Can this change be reversed?

You have boiled some milk on a hot summer day. On cooling it you forgot to place it in the fridge. What kind of change will take place in the milk after 12 hours and why?

On cold chilly day Rakesh tried to open the metallic cap of an ink bottle. He found that metallic cap is struck. His mother told him to pour hot water on it. He poured hot water on the cap for a minute. He again tried to open the metallic cap. Now the metallic cap opened easily. He surprised and asked his observation to his elder brother Samir. Being a student of science Samir explained such things properly.
Answer the following questions based on above information :
   (i) What are the values displayed by Samir?
   (ii) Why was it easy to open metallic cap when warmed with water?
   (iii) What kind of change does take place in the cap of bottle and why?