Science Forum
This forum is to talk about science and conduct some simple experiments, using things you can probably find around the house. You might like to share some ideas of your own. Send us an email.
To set the ball rolling, here's a simple experiment you might like to try.
Magnetic wood
You'll need:
some toothpicks; a dish or pan, at least 6 inches (15 cm) across; nail clippers, or a pair of kitchen scissors; some dish soap (washing-up liquid)
Fill your container with cold water, almost to the top, and leave this to settle. Meanwhile, snip the point off one end of a toothpick. You need a clean edge so, if it looks ragged, snip off some more. Cut off about a 1-inch (2 cm) length, again making sure that the edge is clean. Carefully lower this rod onto the surface of the water, keeping it well clear of the edges. If it does touch the side, just give it a gentle nudge toward the center. Once the rod has stopped moving, you can begin the experiment.
While holding one end of a toothpick just beneath the surface, move it slowly toward one end of your floating rod, as shown in the photo.
As you move the toothpick even closer, you'll find the rod becomes attracted toward it. And when you move the toothpick away, it'll follow, as if they were magnets. If you've got some pistachio nuts, try making a boat from one of the shells--it works even better than a toothpick rod. So what's going on? This all has to do with surface tension.
Surface tension
To understand surface tension you have some idea of the way water molecules behave. Molecules, as you probably know, are those minute particles that all things are made of--way too small to be seen with ordinary microscopes. The water molecules are attracted to one another from all directions. Each molecule is like a popular person at a party, being pulled this way and that. But the water molecules at the surface are all pulled inward because there are no water molecules above the surface to pull them outward. This inward pull on the surface molecules is called surface tension, and holds the surface together like a thin skin. This is why water forms into droplets. Surface tension also explains how some insects, like water boatmen, can walk on the surface of a pond. You can check how this works with a simple experiment. next...
To set the ball rolling, here's a simple experiment you might like to try.
Magnetic wood
You'll need:
some toothpicks; a dish or pan, at least 6 inches (15 cm) across; nail clippers, or a pair of kitchen scissors; some dish soap (washing-up liquid)
Fill your container with cold water, almost to the top, and leave this to settle. Meanwhile, snip the point off one end of a toothpick. You need a clean edge so, if it looks ragged, snip off some more. Cut off about a 1-inch (2 cm) length, again making sure that the edge is clean. Carefully lower this rod onto the surface of the water, keeping it well clear of the edges. If it does touch the side, just give it a gentle nudge toward the center. Once the rod has stopped moving, you can begin the experiment.
While holding one end of a toothpick just beneath the surface, move it slowly toward one end of your floating rod, as shown in the photo.
As you move the toothpick even closer, you'll find the rod becomes attracted toward it. And when you move the toothpick away, it'll follow, as if they were magnets. If you've got some pistachio nuts, try making a boat from one of the shells--it works even better than a toothpick rod. So what's going on? This all has to do with surface tension.
Surface tension
To understand surface tension you have some idea of the way water molecules behave. Molecules, as you probably know, are those minute particles that all things are made of--way too small to be seen with ordinary microscopes. The water molecules are attracted to one another from all directions. Each molecule is like a popular person at a party, being pulled this way and that. But the water molecules at the surface are all pulled inward because there are no water molecules above the surface to pull them outward. This inward pull on the surface molecules is called surface tension, and holds the surface together like a thin skin. This is why water forms into droplets. Surface tension also explains how some insects, like water boatmen, can walk on the surface of a pond. You can check how this works with a simple experiment. next...
