Physical and chemical changes occur around us all the time - lakes melt, fires burn, and pots of water boil.
During a physical change, an object changes its appearance but remains the same chemically that it was before the change.
An example of a physical change is ice cubes melting. The water in the ice cubes changes from solid to liquid but the chemical formula of the water remains the same (H2O).
A chemical change occurs when a substance undergoes a reaction that changes its chemical makeup.
When a fire in a fireplace burns, the wood is transformed into carbon dioxide and water. The material in the wood undergoes a chemical change because water and carbon dioxide have different chemical properties than wood.