The true descriptions for chemical changes are:
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The chemical and physical properties change during a chemical reaction - This is true, as a chemical change involves reactions that result in new substances with different properties.
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There are the same number of atoms before and after the change - This is also true, as the law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction, so the number of atoms remains constant.
The other statements are false:
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The identity of the substance stays the same - This is false because a chemical change results in new substances with different identities.
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Cutting down a tree is an example of a chemical change - This is false because cutting down a tree is a physical change; it alters the physical state of the tree but does not change its chemical structure.
So, the correct answers are:
- The chemical and physical properties change during a chemical reaction
- There are the same number of atoms before and after the change
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