Which will be more dense 30ml of a salt solution or 30ml of pure water?

When salt is dissolved in water, like the ocean, that dissolved salt adds to the mass of the water and makes the water denser than it would be without salt. This is why objects like ships float in the ocean, because objects float better on denser water rather than fresh water.

Therefore, your answer would be 30ml of salt water would be denser.

hope this helps!

It's a

Temperature and pressure