Ship!!!

Place a half-dollar or 10 new pence on the table and on one side of the coin a small cork disk. How can you move the cork to the exact centre of the coin without touching it!

Pour water on to the coin - drop wise, so that it does not spill over - to form a water mountain over the surface. At first the force of gravity holds the cork on the edge of the slightly curved water surface. If you now pour on more water, the pressure of the water on the edge increases, while it remains constant on the top. So the cork moves up the hill to the middle, which is the region of lowest pressure.

Mountain Of Water

Fill a dry glass just full with tap water, without any overflowing. Slide coins carefully into the glass, one after the other, and notice how the water curves above the glass.

It is surprising how many coins you can put in without the water spilling over. The water mountain is supported by surface tension, as though it is covered by a fine skin. Finally, you can even shake the contents of a salt cellar slowly into the glass. The salt dissolves without the water pouring out.

Water knots

An empty two-lb. can is pierced five times just above the lower edge with a thin nail. The first hole should be just over an inch from the fifth. Place the tin under a running tap, and a jet will flow from each hole. If you move your finger over the holes, the jets will join together. The water particles are attracted to one another and produce a force acting into the interior of the liquid, the surface tension. It is also this force which holds a water droplet together. In our experiment the force is particularly clear, and it diverts the jets into a sideways are and knots them.

String of pearls

Let a fine jet of water pour on a finger held about two inches under the tap. If you look carefully, you will see a strange wave-like pattern in the water. If you bring your finger closer to the tap, the waves become continuously more ball-shaped, until the water jet resembles a string of pearls. It is so strongly obstructed by the finger that because of its surface tension - the force that holds the water particles together - it separates into round droplets. If you take your finger further away from the tap, the falling speed of the water becomes greater, and the drop formation is less clear.

Ice hook

Who can hook an ice cube from a bowl of water with a match? A trick makes it quite easy: place the match on the ice cube and scatter some salt over it. In no time the match is frozen solid, and you can lift it together with the ice cube from the dish.

Salt water does not freeze as easily as ordinary water, and scattering salt on ice makes it melt. The salt grains on the ice cube also do this. However, when a substance melts, heat is consumed at the same time. This heat is taken from the moisture under the match, where no salt fell, in this case - and it freezes.

Cutting Through Ice

Place an ice cube on the cork of a bottle. Fix two objects of equal weight on a piece of wire, hang the wire over the ice and place the whole lot out of doors in frosty weather. After a certain time the wire will have cut through the ice without dividing it.

This trick of nature is explained by the fact that ice melts when it is subjected to pressure. Water is formed where the wire is resting, while it immediately freezes again above it. Skating is only made possible by slight melting of the ice under the moving surface, which reduces the friction.

Iceberg

Place a cube of ice in a tumbler and fill it to the brim with water. The ice cube floats and partly projects from the surface. Will the water overflow when the ice cube melts!

The water increases its volume by one-eleventh when it freezes. The ice is therefore lighter than water, floats on the water surface and projects above it. It loses its increased volume when it melts and exactly fills the space, which the ice cube took up in the water. Icebergs, which are a danger to navigation, are therefore especially harmful because one only sees their tips above the water.