- A raw, unpeeled potato
- Straight plastic drinking straws
What to do
- Gather your materials on a flat surface.
- Place the potato on the flat surface and hold it steady with one hand.
- Grasp the middle of a straw firmly without bending or crushing it. Leave the top end of the straw uncovered.
- Hold the straw about 10 cm above the potato and then stab the straw into the potato. What happened?
- Using a new straw, place your thumb over the top end of the straw to make an airtight seal. If it’s a bit hard, try using half a straw. Just be careful cutting it with the scissors!
- Hold the straw 10 cm above the potato. Once again, stab the end of the straw into the potato. What happened this time?
Questions to ask
What happens if you make a partial seal over the straw? Try stabbing the potato again, but leave a little bit of an opening so a bit of air can get out.
Which method was best for making tiny little chips? Why do you think that is?
Air is all around us. Air pushes on things, even us. That’s called air pressure. We don’t really notice this because we are used to it.
Air pressure allows things to hold their shape. Think about how pumping air into a football or bike tyre makes the object firm. This is because you are increasing the air pressure inside that object.
In this experiment, the air gets trapped in the straw when one end is covered by your thumb and the other end touches the potato. When the straw pushes on the potato, the air pressure inside the straw allows the straw to hold its shape. You can then poke out a little piece of potato.