In a chemical change the original substance is changed into one or more different substances with different properties. When a candle burns it becomes shorter. Some wax may melt down the side candle but some seems to disappear. What happens is when the wax burns some of the wax particles react with the oxygen around them to produce water vapour, carbon dioxide gas, heat and light. the wax particles that look like they are disappearing are actually just changing into other substances. You might be wondering why i have a picture of fireworks on a chemical change page. What happens with fire works are two substances get shot up into the sky and at the perfect moment when the meet an explosion happens. The difference between a physical change and a chemical change is that in a physical change it is the same substance just in a different state but with a chemical change the original substance is changed into one or more substances.