We have already learned about different kinds of angles:- right angles, acute and obtuse angles. To make a spray you need to be able to make right angles and acute angles with two straws. Before we tried this, we loved predicting what would happen. (You can't make a spray if the two straws make an obtuse angle. In this case the air you breathe will rush down the straw and just make bubbles in the water below). By blowing the air at the top of the straw you create a vacuum. The air and then the water in the straw rush up to take the place of the air blown away. This water gets blown into a spray.