- A clear empty jar or bottle, preferably plastic
- Basmati rice (you will need slightly more rice than the jar or bottle can hold)
- A wooden spoon or wooden chopstick
What to do
- Gather your materials on a flat surface.
- Fill the jar with rice.
- Push the spoon or chopstick into middle of the rice. Wiggle it around, then pull it out.
- Do this once more. You should see the level of the rice beginning to fall.
- Add some extra rice until the container is full again.
- Keep pushing the spoon or chopstick into the rice, wiggling it around, and pulling it out. Do this for a few minutes, adding extra rice whenever there is empty space at the top of the jar.
- After a few minutes, you should notice that it becomes more and more difficult to push the spoon or chopstick into the rice. Eventually, you should be able to lift up the jar just by pulling on the spoon or chopstick. It’s stuck in the rice!
Questions to ask
What happens to the rice every time you push the spoon or chopstick in and wiggle it around?
Does the type of rice you use make any difference? Try using white rice, brown rice, jasmine rice – any other type of rice you have.
Can you get this experiment to work using something other than rice?
When the jar is first filled with rice, the rice grains are facing in many different directions and there are lots of small air holes between them. When you first push the spoon or chopstick into the rice, there is space for the rice grains to move out of the way. By wiggling the spoon or chopstick around, you force the rice grains to line up with each other and fill any gaps. This reduces the amount of air space (sometimes called pore space) between the rice grains. They get packed in more tightly.
When the rice grains are packed together more tightly, they push harder on the spoon or chopstick. Friction is a force that happens when 2 objects rub against each other. It stops the surfaces from sliding. The spoon or chopstick will feel more friction if more rice touches it directly. It will feel more friction if rice is pushed against it harder. Both these things happen as the rice packs in tighter. Eventually, there is so much friction that you can lift the jar of rice using just the spoon or chopstick!
Did you know
The settling and lining up of the rice grains is similar to how potholes in roads are made. Over time, vibrations from cars can cause stones in the road to pack together more tightly. They don’t take up as much space, leaving empty space – a pothole.