Very short and easy experiment to explain surface tension to kids. Pour water on a plate, sprinkle glitter on top, dip finger in dish soap and watch the glitter floating away from the finger.
Why: water molecules cling toghether and they arrange themselves to create a force/energy called surface tension. Glitter does not mix with water and it is light to sit on the water without breaking the surface tension. When you add the soap – it breaks the tension and because water molecules like to stick together, they spread away from the soap taking with them the glitter sitting on top.
Explore more surface tension experiments here.