Question

(i) Differentiate between a physical and a chemical change. Write any two differences. Classify the following as physical or a chemical change :
(a) Water freezes to form ice
(b) Sugar is dissolved in water
(c) Burning of paper
(d) Rusting of an iron nail.
(ii) Give an example where physical and chemical changes can take place simultaneously.

CBSE Class IX Science LA (5 Marks)

Answer 1

I) Physical change:-
1)The change is most likely reversible
2) The substance obtained retain its properties
Chemical change:-
1)The change is irreversible
2)The substance obtain have totally different properties.

Physical change:-
a) water freezes to ice
b) sugar is dissolved in water

Chemical change:-
a)burning of candle
b)rusting of iron nail

II) EG - Burning of candle. Mealting of candle wax is physical change but burning of wick is chemical change.

Answer 2

(i)  Difference between physical and chemical changes :

S.No.                      Physical change                           Chemical Change

(i)                These are reversible changes             These are irreversible                       and their chemical composition            changes and the chemical
                  do not change.                                 composition also changes.

(ii)      No new substance is formed. e.g.,     New substance is formed. e.g.,             Tearing of paper.                                 Burning a match stick.

(a)  Water freezes to form ice ------Physical
(b)  Sugar is dissolved in water----Physical
(c)  Burning of paper                ----chemical
(d) Rusting of an iron nail        ----chemical

(ii) In burning of wax both physical and chemical change is taking place simultaneously.