Question

Sarita while helping her mother in kitchen work noticed that the slices of potato and brinjal have acquired a brown colour. She asked her mother reason behind this change. Her mother said whenever we keep cut pieces of these vegetables open for long time they acquire such colour.

(a) Are cutting vegetables and change in colour, physical or chemical changes?

(b) Why vegetables acquired brown colour?

(c) Do this brown colouration indicate that the vegetables are spoilt. Can

we reverse this process? Why?

(d) Can you suggest ways to avoid this colouration of vegetables? (e) What value of Sarita is shown here?

Q2. When we keep a piece of iron in the open area for few days, a brownish, flaky substance, called rust, is deposited on it.

(a) Is rust different from iron?

(b) Is formation of rust from iron a chemical change? (c) Can you change rust back into iron by some simple method?

(c) Give some other examples of a similar type of changes.

Q3. Give an example of a chemical reaction for each of the following situations: (a) A change in colour is observed.

(b) A gas is evolved.

(c) Sound is produced. (d) Heat is produced.

(e) Change in taste is observed

Answer 1

Change in taste is observed