2. Aristotle-->e, Cavendish-->c, Lavoisier-->f, Priestley-->b, Proust-->d, Gay-Lussac-->a

4. Chemical, chemical, chemical, physical, chemical, chemical, chemical

6. No. Oxygen and hydrogen are both gasses at room temperature, but when combined form a liquid (water).

8. MgCl₂

11. nonpolar, nonpolar, polar

14. Water molecules are polar while methane molecules are not. Polar molecules stick together better than nonpolar molecules.

15. O with F-->covalent, Ca with Cl-->ionic, Na with Na-->metallic, U with Cl-->ionic.

16. ammonium cyanide, diammonium sulfate.

17. Pour the sand/salt mixture into water, the salt will dissolve into the water. Pour the water/sand/salt mixture throuth a filter, to filter out the sand. Finally, boil the water away to get the salt.

Melt the iron.

1. 25 grams of hydrogen will combine with 200 grams of oxygen to form 225 grams of water. 25 grams of oxygen will be left over. Recall 8 grams of O will bond with 1 gram of H.