What is it called when a gas is converted into a liquid

What is the formula that this ionic compounds could form sr2+p3-o2-

Between 2014 and 2016, more than 25,000 children in flint, michigan, drank water that was contaminated with lead from lead pipes. during this time, the city claimed the water was safe to drink. which of these actions could the city have taken to ensure that the drinking water was free from lead?

Choose all the answers that apply. as ocean depth increases, temperature decreases temperature increases pressure increases pressure decreases salinity increases density increases