Describe an experiment to explain the difference between melting and burning.
Burning of candle is the best experiment which shows both melting of wax and burning of wax.
On heating wax it melts but when we cool it down we get back the solid wax, while if we take the case of wick in the candle then it decomposes to give water and carbon di-oxide, which makes it irreversible and hence a chemical change
When a candle burns, the wax does two things. First it melts, and then it burns. What burns is actually melted wax! The heat of the candle melts the nearby wax, and that melted wax is absorbed by the candle's wick. The melted wax burns on the wick -- the wick itself isn't burning, just the wax on it. However, as the candle burns down, what happens is there isn't enough wax nearby to melt, and so the end of the wick does burn a little, which is why it slowly gets shorter (at the same speed as the candle gets shorter). It is a chemical change because there is new matter (buring of the wax resulting in the formation of carbon dioxide and water vapour) created but flammability is more of a property than a chemical change. A physical change is still the same matter but is in a different form like cutting paper. Its still paper. But if you burn paper, that's a chemical change because its new matter now and its really hard to change back