1.

Classify the following as physical and chemical changes. Give reason for your answer. (a) Burning of candle.(b) Melting of ice.(c ) Burning of petrol in an engine.(d) Change of colour of iron bar on strong heating(e) Churning of milk to get butter.

Answer»

Solution :(a) Chemical change :
(b) Physical change : When WATER formed as a result of melting of ice is cooled to `0^(@)C`,it changes back to ice.
(c ) Chemical change : Petrol is a mixture of different hydrocarbons. They undergo oxidation or combustion upon burning to FORM carbon dioxide and water vapours ALONG with heat energy. Therefore, it is a chemical change.
(d) Physical change : Iron bar regains its colour on cooling.
(e) Physical change : There is only a change of physical state and no NEW SUBSTANCE is formed.


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