Explain how mass and energy are conserved when water evaporates.

The water molecules that are evaporationg absorb heat energy from the surrounding environment, which causes the evaporation. If 5 grams of water evaporate, then there will be 5 grams of water vapor in the air.

Mass is conserved  as the water which evaporates appears, heat is needed for the evaporation is taken from a liquid and is conserved 

Density and pressure

So what you would do is go through and add 3 teaspoons(tsp) 6 times because of the 6 tablespoons(tbsp). which will give you an answer of 18. another way is to multiply 3x6=18.