The true descriptions for chemical changes are:
- The chemical and physical properties change during a chemical reaction.
- There are the same number of atoms before and after the change.
The first statement about cutting down a tree is not a chemical change, as it primarily involves a physical change (removing the tree) rather than altering its chemical structure. The statement about the identity of the substance staying the same is also false for chemical changes, as the identity of the substances involved can change.