Metal paper clips are handy for a variety of scientific demonstrations.
Metal paper clips are handy for a variety of scientific demonstrations.

You can perform several easy science experiments using small paperclips and a handful of other household items. The steel in traditional metal paperclips consists mostly of iron, making them useful for demonstrating magnetism, the chemical reaction that causes rust, and other scientific principles. The experiments presented here use common steel clips, although any light clip works for the last experiment.

Rusting Metal

Remove most of the bright coating from several steel paper clips by light scrubbing with sandpaper. Lay the clips flat on a paper towel set on a table or desktop and moisten them with an ounce or two of water mixed with a pinch of salt. Let the paper clips sit on the paper undisturbed for several days and note how long it takes for them to rust. Take pictures every day at about the same time and note the progress of the rust. Some of the iron atoms in the paper clip lose electrons to other parts of the clip as they combine with oxygen, forming a brown-orange rust compound.

Induced Magnetism

Because steel paper clips contain iron, you can easily magnetize them with a strong magnet. Obtain a bar magnet and lay it on a non-metallic desk. Stroke the magnet with the paper clip by moving it from the south pole to the north, lifting it from the magnet, then bringing it to the south pole again and moving it to the north; by repeating this 20 or more times, you magnetize the clip. An ordinary paper clip has tiny magnetic zones called domains, each of which has a north and south pole; however, they all point in different directions and their net magnetism cancels out. By stroking the clip with the magnet, you orient the magnetic poles of some of the domains so they point the same way, creating a magnetic field around the metal. You can test the paper clip by picking up loose staples or other small metal objects.

Metal Fatigue

A phenomenon called metal fatigue causes many type of metal objects to break when flexed or bent several times. You can easily see this in a paper clip if you bend it open to an “S” shape, then bend it closed again, repeating the process a few times. Observe where the metal bends; it becomes visibly strained before breaking. You can measure the effect of the bending with a 50-gram weight hanger and some gram weights. Bend a paper clip open and hook the weight hanger on bottom of the lower half. Add several 20-gram weights and note how many the paper clip can support. Bend the clip closed, then open again and retest its weight-holding ability. Repeat the process a few more times and note the total weight at which the clip breaks.

Surface Tension

Surface tension is a property of most liquids; the molecules at the surface cling together more strongly than those inside the liquid, forming a thin barrier of modest strength. To demonstrate this, obtain a small paper clip, a bowl of clean water and some soap. Carefully lay the clip on the surface of the water so it doesn’t sink; this make take a few tries. The water’s surface tension keeps the clip from sinking. Being careful not to disturb the water, add a dab of liquid soap or touch a bar of soap to the water for a few seconds. The soap reduces the water’s surface tension and the clip sinks.