Surface Tension
Surface Tension is the thin, stretchy skin that forms on top of water because water pulls itself together.
Water has a thin, stretchy layer on its surface, like plastic wrap stretched across a bowl. Small, light things like a paper clip can rest on top without sinking. The water at the top pulls toward itself, forming a skin that holds the weight. Push through that skin, and the object drops to the bottom.
Explaining surface tension by grade level
Water has a thin skin on top. That skin is strong enough to hold up small things. When you add soap to water, it breaks that skin. That is why soap bubbles pop when the skin gets too weak.
Projects that explore surface tension
Water pulls itself together into a thin, stretchy skin — and a soap bubble is that skin shaped into a sphere. How long the bubble lasts depends on what you add to the soap solution. You prepare five mixtures, each with a different additive: corn syrup, glycerin, sugar, lemon juice, and plain soap as a control. Blow a bubble from each, start a stopwatch, and record how long it holds before it pops.
Water molecules cling tightly together, forming a thin, stretchy skin on the surface. That pull — called surface tension — keeps oil floating in a separate layer on top. You add vegetable oil to a jar of water and watch the two layers stay apart. Then you add liquid soap and stir. The soap breaks the surface tension, and as a result the oil blends in.