Fill a glass of water to the rim, allowing a slightly convex shape to the water's surface. Slowly bring quarters to the center of the glass above the water. To minimize disruption to the surface, place the narrow edge of each quarter into the water and let go. Continue filling the water with quarters as the convex shape of the water becomes more pronounced, thus illustrating surface tension.
Again, fill a glass of water to the rim. Place a sewing needle on a fork and carefully lower it into the glass of water. Pull the fork out of the water, leaving the needle to float. As long as the needle stays dry, this will work, but if the needle becomes wet, it will sink. This may require some practice to remove the fork in such a way that the needle will not get wet.
Coat the large end of a funnel by dipping it into a detergent solution. Then, using the small end of the funnel, blow a bubble that is at least 12 inches in diameter. Place your thumb over the small end of the funnel, trapping the bubble. Bring the funnel toward a lit candle with the small end facing the candle. Remove your thumb from the end of the funnel. This will allow the surface tension of the soap bubble to contract, forcing air out through the funnel and extinguishing the candle.
Cut a fish shape from a piece of paper. Then cut a hole in the center of the fish with a narrow channel of paper trimmed away through the tail end of the fish. The result should look like a fish with a keyhole shape cut out of it. Float the fish on top of a full dish of water. Place one drop of vegetable oil or liquid detergent into the hole in the center of the fish. The oil or detergent will disrupt the surface tension of the water and, after a few seconds, the fish will appear to move across the water.