A chemical change occurs when the chemical composition of a substance changes. For example, when you burn a piece of paper, the paper undergoes a chemical change and turns into ash.

When you open a soda can, you are not changing the chemical composition of the soda. The soda is still made up of the same molecules as it was before you opened the can.

The only thing that changes when you open a soda can is the physical state of the soda. The soda changes from a liquid to a gas. This is a physical change, not a chemical change.