Across
- 1. animals need to breathe ___________.
- 3. elements can stick together to form __________.
- 6. when you mix two elements, there is a chemical ___________.
- 7. elements are special because they are made of one kind of ___________.
- 8. today is _____________ class.
Down
- 2. the periodic table has many ___________.
- 4. __________ is a compound of hydrogen and oxygen.
- 5. even the _______ in your cells is a compound.