Classify the following as a physical or a chemical change. Give reasons:
a) drying of a shirt in the sun
b) burning of kerosene in a lantern
c) burning of a candle
Answers
a) drying of a shirt in the sun is a physical change because no new substance is formed, the water in the shirt is evaporating and evaporation is a reversable change
b) burning of kerosene in a lantern it is a chemical change because when kerosene burns it produce co2 and other gases here new substance(co2) is formed which is not reversable
c) burning of a candle When a candle burns, both physical & chemical changes occur.
Physical Changes in Burning Candle: On heating, candle wax melts and form liquid wax. It is a physical change. Since it again turns into solid wax on cooling. This is a reversible change.
Chemical Changes in Burning Candle: When you light the candle, the wax present near the wick will melt. Wick absorbs the liquid wax. The liquid wax vaporizes due the heat produced by the flame. This wax vapor near to flame burns and gives new substances like Carbon Dioxide,(wax + O2 → CO2(g)+ heat +light)