Which material is a mixture? a water b methane c air d magnesium

Suppose you mix one mole of sulfuric acid (h2so4) with 1 mole of sodium hydroxide(naoh). why does the ph of the solution remain below 7? ( explain so i can get better understanding! )

What would happen to a volleyball left outside in the winter? o o o o a. it would expand. b. it would lose air. c. it would shrink. d. it would explode.

Acompound has the molecular formula c3h8. which class of organic compounds does it belong to?