Home experiments

In honour of National Science Week, here’s some scientific investigations you could try at home – if you have understanding parents, that is…

Our experiment in Flipside magazine using a bottle of Coca Cola and a tube of Mentos wasn’t as spectacular as we hoped. But there’s plenty more where that came from. Here's a few more you might like to try with bits and pieces you may have around the home. Some involve food so ask your folks if it's OK before launching into your experiments. Also think where you are going to do them, preferably places where any mess is easily cleaned up.

Bendy water

You need:
Plastic comb
Decent head of hair
Running water
Runny honey or golden syrup

Here's what to do:
Comb your hair with the plastic comb for 30 seconds or a minute. Go into the bathroom or kitchen and turn on the cold tap so it's a thin, steady stream, not breaking up into droplets.
Put the comb close to where the water comes out of the tap and you will see the water attracted towards the comb. It can be quite dramatic.
You can do the same with honey or golden syrup but remember to pour it in a very thin stream from a spoon into a bowl and not onto the floor. It can look even more spectacular than water.

It happens because:
As the comb passes through the hair, friction causes a build up the electrons that makes the comb negatively charged. Water is electrically neutral but the molecules do have regions of positive and negative charge. The combs’ strong negative charge attracts the positive parts of the molecules while pushing away the negative parts, causing the water to bend. It's called the Doff effect.
Honey or treacle move slower than water so the negative comb has more time to effect the molecules making the sticky stream bend even more.

Rambo Rice

You need:
Plastic jar, about 500ml in volume
Rice to fill the jar, about 1kg, uncooked
Sharp knife
Confidence
A grown up standing by

Here's what to do:
Fill the jar to the top with rice, then plunge the knife into the rice at different angles several times making sure it doesn't go through the side of the jar. Jab the knife straight down into the rice up to its handle.
Pull straight up on the knife and it will lift the jar of rice with it.

It happens because:
The thousands of grains of rice exert such a force of pressure that it can overcome the effects of gravity. The first stabs settle rice so that it becomes tightly packed. However the knife is sharp and thin enough to break through this tight network of pressure before the grains quickly settle back on all sides, trapping the knife in place.

Rubber chicken bone

We tried this with Coke and it didn't work. Vinegar should be more effective.

You need:
Chicken drumstick, once you’ve eaten all the meat of it
Jar big enough to hold the bone
Vinegar

Here's what to do:
After dinner, clean the chicken bone thoroughly and rinse in water. Put the bone in the jar and cover it with vinegar. Fasten the lid (otherwise the whole house will pong of vinegar) and leave it sitting for about three days. Take the bone out of the vinegar and rinse it off under running water and see how weird it feels.

It happens because:
You've heard about why it is important to drink milk and eat dairy products because they are a good source of calcium, which helps to build up our bones. But did you know that calcium also keeps our bones rigid?
It's the same for chickens and vinegar, a mild acid, dissolves the calcium making the chicken bone go all floppy.

The CD hovercraft

You need:
A unwanted CD or DVD, preferably S Club or Cliff Richard, although this won't affect the performance
Plastic bottle top
Strong glue such as Uhu or Super Glue
Balloon
Patience, it takes a little time to get it all working

Here's what to do:
Firstly, make a hole in the cap a bit smaller than the hole in the CD. Glue the cap onto the centre of the CD so the holes alight and the flat side of the cap is on the CD. If you are using super Glue be very careful not to get it on your fingers.
Blow up the balloon and twist the end around tight but don't tie it. Now with the balloon still twisted so that the air can't escape, carefully roll the edge of the balloon over the cap and then, still holding the balloon, place the CD on a smooth surface and let go. With the slightest push the CD hovercraft should glide along the surface.

It happens because:
The air from the balloon rushed out through the hole creating a cushion beneath the CD. The air supports the entire CD because it is escaping equally on all sides and the air cushion has eliminated any friction between the CD and table top surface so the CDcraft can more about freely.