When a candle is lit, it undergoes both physical and chemical changes:Physical change: wax melting, melted wax vapourisationChemical change: The combustion of wax vapours produces carbon dioxide, heat, and light.When LPG flows out of the cylinder and is transformed from liquid to gaseous state, a physical change occurs, and a chemical change occurs when gas burns in the air.To do well in tests, you should go through all of the NCERT questions and obtain a thorough understanding of all of the Chapter 6 of Class 7 Science provided by Vedantu on its website(vedantu.com) or mobile app.