1) Consider the law of conservation of mass as you answer this problem. When ammonium nitrate (Nh4NO3) breaks down explosively, it forms nitrogen gas (N2), oxygen gas (O2), and water (H2O). When 40 grams of ammonium nitrate explode, 14 grams of nitrogen and 8 grams of oxygen are formed. How many grams of water are formed?

2) Hydrogen and Oxygen react chemically to form water. How much water would be formed if 4.8 grams of hydrogen reacted with 38.4 grams of oxygen?

I read somewhere that you had to use moles but is there another method because I have not learned about moles yet.

3) State several physical or chemical properties that could be used to distinguish between each of the following pairs of substances and mixtures.
a. gasoline and water
b. copper and silver
c. water and a saltwater solution
d. aluminium and steel

I put for:
a. color, odor, composition?
b. color, composition, hardness?
c. taste, odor?
d. color, hardness?