NCERT Question 5 - Chapter 6 Class 7 - Physical and Chemical Changes

When a candle burns, both physical and chemical changes take place. Identify these changes. Give another example of a familiar process in which both the chemical and physical changes take place.

Answer:

When a candle burns, both physical and chemical changes take place.

• Physical change - Melting of wax
• Chemical change - Burning of wick

Another example that can be considered is of LPG. 

• The gas we use in the kitchen is called liquefied petroleum gas (LPG). 
• In the cylinder it exists as a liquid .
• When it comes out from the cylinder it becomes a gas (Physical change) and then it burns (Chemical change) producing vapour and smoke.