It's not a mouse, it's a water molecule. Since the hydrogen atoms are both on the same side of the oxygen atom, water molecules have a positively charged side and a negatively charged side.
You will need
A balloon
A tap and sink
A cup
What to do
Inflate the balloon and tie it off.
Turn the tap on so the water is coming out in a slow steady trickle. (To conserve water, you can catch the water in a cup and drink it later.)
Rub the balloon against your hair, to give it a static electricity charge.
Hold the balloon near the water, but don't let it touch.
What does the water do?
What's going on
You should find the water bends towards the balloon. I was able to pull my stream of water several centimetres out of its way as it fell.
When you rub the balloon against your head, you give it a negative electrical charge. This makes it attract things with a positive electrical charge and repel things with a negative charge.
A water molecule contains a negatively charged oxygen atom with two positively charged hydrogen atoms attached to it. The hydrogen atoms are both on the same side of the oxygen atom, so one side of the water molecule has a negative charge and the other side has a positive charge.
When you hold the balloon near the water, the hydrogen atoms are attracted and the oxygen is repelled. This always used to confuse me: why didn't the repulsion of the oxygen cancel out the attraction of the hydrogen?
It turns out that as a water molecule comes near the balloon, the attraction and repulsion makes it spin around so the hydrogen side is closer to the balloon. When that happens, negatively charged side of the water molecule is further away from the balloon than the positively charged side. This means the force repelling the negative side is less than the force attracting the positive side, so it doesn't cancel out. The total force on the water molecule pulls it towards the balloon
As the water molecules pass by the balloon, they turn so the hydrogen atoms face towards the balloon.
Molecules where one end has a positive charge and the other end has a negative charge are called polar molecules. This week, we have seen that water is a polar molecule.
There are several properties of materials that depend on whether or not its molecules are polar. For example:
Sugar and salt will dissolve in water, but not oil (oils are generally non-polar).
The chemical that makes chillies spicy will dissolve in oil but not water.
Polar molecules normally have higher freezing and boiling points than similar non-polar molecules.
