See explanation below
Chemical changes are changes that, simply put, indicate some kinds of chemical reaction. Some signs of chemical changes are:
- Release of heat.
- Formation of new compounds, with new chemical properties.
- Releasing of a gas (ties in with #2).
- Color change.
The most significant property of chemical changes, however, is #2 - that you form new compounds with different chemical properties. All the others are often indicators of chemical change, but could just as easily be indicating a physical change - in which there is no change in chemical properties.
Hope that helped :)