The air we breathe is not considered by chemists to be an element. why not

Explanation:

An element is a substance that cannot be broken down by an ordinary physical process. An element is made up of atoms having the same atomic number. There is a periodic table of elements that has all the elements arranged according to there atomic number.

Air is not an element because it actually contains atoms of more than one element (including oxygen, nitrogen and noble gases). Air also contains compounds such as CO₂. These substances that air contains are physically combined, hence air is a mixture.

answers: to make sure that all of the broken pieces of tablet were added to the water, to allow for fair comparison of all three trials, with different particle sizes to avoid experimental error