A WAY to categorize chemical reactions is by looking at the heat involved in the change. 

EXOTHERMIC reactions release heat as they occur.  A common example is a burning fire...

This is clearly a chemical change because of the obvious new substances that are formed... the atoms present in the wood combine with oxygen from the air to produce gases, smoke, and release heat.

ENDOTHERMIC reactions absorb heat as they occur.  Without adding heat, they will not happen.  A common example of an endothermic reaction is cooking food...

IS IT CLEAR to you that cooking food is really a chemical change?  Can you easily get back your raw eggs once they're fried?  The atoms have become rearranged while absorbing heat.