Everything in the universe is made of matter, but not all matter is the same. Matter can be sorted into one of four different categories – solid, liquid, gas, or plasma. Some molecules will only ever be found in one of the four states, while other molecules can shift from one state to another, depending upon the conditions surrounding that molecule.
One of the things that can make a molecule shift from one state to another is temperature. When we think of water, we usually think of the liquid that comes out of our faucet, falls from the sky as rain, or fills creeks, rivers, ponds, lakes, and oceans. The water in these examples is in liquid form, but if you heat up water, it changes. It stops being a liquid and becomes a gas called water vapor. Another common name for this vapor is steam. Similarly, when liquid water gets really cold, it changes state again. This time it becomes a solid – ice.
Different states of matter are organized differently at the atomic level, as demonstrated in the picture. The more energy that molecules are exposed to the more “excited” they become, and they start to move around more. Exposing water to increasing or decreasing amounts of energy, in the form of heat, causes the water to change its state. Molecules may need a different amount of space, depending upon what state they are in.
The Experiment
Supplies: A freezer-safe container with a lid, water
What to do: Fill the container with as much water as you can while still being able to carry it without spilling! Set the container in the freezer where it won’t be disturbed for several hours. Now, add more water, until the container is filled all the way to the brim. Set the lid loosely on the top. DO NOT TIGHTEN THE LID. After several hours, come back to check on your container. What happened to the water? What happened to the lid?
What is happening: As with the water/rubbing alcohol experiment, when water is in its liquid form, the molecules can squish together more easily. In its solid form (ice) the water molecules take up more space, so the water will expand in volume as it freezes. For a variation of this experiment, pour 1/2 cup of water into a liquid measuring cup. Make sure the water is to the line. Freeze your measuring cup and water for several hours. Where on the measuring cup is the surface of your ice?
Links
For more information on states of matter, check out the Chem4Kids website.