A wire ring 10 cm in diameter has a flexible loop of thread tied to it. It is dipped into a soap solution and removed. A thin film is formed in which the thread floats freely. If the soap film inside the loop of thread is punctured, the thread promptly spreads out into a circular shape.
A cork and sinker are connected by a stiff wire to a wire ring. In a large beaker filled with water, the set is buoyant with the ring high above the water. Now push the set down into the water and allow it to rise again, slowly. When it reaches the surface, the ring will not break the surface: it will remain submerged due to the water's surface tension.
There are two sets of four interconnected capillary tubes of varying diameters. One set is filled with colored water, the other set is filled with mercury. They show the dependence on the height of the capillary rise of liquids on the tube bore. Water rises higher in the smaller diameter tubing, whereas mercury is lowered in the smaller diameter tubing.
A large beaker filled with water is placed on a rotating platform. When the platform rotates, centripetal force acting on the water's surface will cause it to form a paraboloid.