The first scientific concept is that of density of liquids. Notice that the oil sits on top of the water. Is water lighter or heavier than the oil? What happens to the paint?
The next concept is that of the reaction once the tablet is dropped into the cup. This is what creates the awesome snow storm effect. The tablet contains both an acid and a base that when mixed with water, creates the bubbles. The bubbles are a result of the carbon dioxide gas that is released during the chemical reaction. To make the snow effect, the bubbles pick up the white paint and carry it to the surface. Once the bubbles reach the surface they pop and the paint/water mixture drops back down.