1. Physical changes are changes affecting the form of a chemical substance, but not it’s chemical composition.
2. A usually irreversible chemical reaction involving the rearrangement of the atoms of one or more substances.
—— remember a physical change you can see the desperate piece in a mix, such as a salad. A chemical change is when you cannot, like if you mix to salad dressings together, you cannot pick them apart again.—-
3. States that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations.
4. ^^^ example after question 2.
5. Chemical - you cannot reverse the change — separate the two salad dressings — physical- you can pick pieces apart — you can remove the tomatoes from the lettuce in a salad.
6. The majority of the log has been turned to ash, therefore making most of it into a gaseous form, which is irreversible and much lighter.
7. All are chemical. Those are all changes you cannot reverse.
8. Once you burn a paper into nothing, you cannot reverse the change and make it into paper again.
9. This would still be a physical change. The pieces are only separated, but the object did not chemically change.
Hope this helped!!