Most people are familiar with three states of matter: solid, liquid and gas. Actually, if you dig into the world of physics, there are several more, but for now we will only add plasma to the list, and we will look at the first three states before talking about plasma.

Solid

Things like rocks, wood and ice are solid. Solids stay the same size and shape, no matter what container we put them in.

Liquid

Things such as alcohol, oil, and water are liquids. They stay the same size, but they change their shape to fit their container.

Gas

The most common gas, the air, is actually a mixture of several gases. Gases change their shape to fit their container, just as liquids do. They also change their size to fill their container.

Plasma

The fourth state of matter is called plasma. Do not confuse this plasma with the plasma in blood. That is something completely different. Plasma as a state of matter is similar to a gas. It changes it's size and shape to fit a container. The difference is that in a plasma, each of the atoms has lost its electrons. These free electrons are moving around between the atoms. For this reason, plasmas are good conductors of electricity. Plasma also gives off light, which makes it easy to see.

The study of matter is one of the most basic sciences. If you dig deep enough, most areas of science are built on a foundation of understanding matter.

Overview

What is Matter?

Before we can dive into the study of matter, we really should know what matter is. Luckily, the definition is short, and fairly easy.

• What is the difference between mass and weight?

States of Matter

What is matter?

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This is another of those fun bits of science that many of us think we understand until we really start to look at it. To try this, you will need:

- water
- two drinking glasses
- a saucer or cover for one of the glasses

Start by taking a glass of water outside. Find a nice, flat spot on your driveway or sidewalk, and pour out the water to make a big, wet spot. Now go for a walk, have a snack, read a chapter in your favorite book, have another snack, and then go back to look at the wet spot. Is it still there?

That will depend on the weather. If it is a very humid day, then it may still be there. If it is cold enough, your wet spot may still be there as a patch of ice. On the other hand, if it is a dry day, especially if it is warm or windy, then you will probably find that the water is all gone. Where did it go? It evaporated of course. But, what happens when a liquid evaporates?

When a substance evaporates, it changes from its liquid form to its gaseous form. Isn't that the same as boiling? But, water has to be hot for it to boil, yet it will evaporate even if the weather is near freezing. How can that be? What is the difference between boiling and evaporating?

The basic process is the same. If the molecules of the liquid have enough energy, they can break away from the rest of the group, launching themselves into the air to become a gas. The difference between the boiling and evaporating is in where the molecules get that energy.

For boiling, the energy comes from heat. Put a pot of water on the stove, turn on the heat, and soon the water molecules in the pot will gain enough heat energy to let them break away in large numbers.

But, if you take that same pot of water, and put it on the table instead, it will still evaporate. Why? Those water molecules are bouncing around, bumping into each other. When they bump, energy can be transferred from one to another, just like the balls on a pool table. If the bumped molecule is in the middle of the pot, it will probably bump into another water molecule, passing along the energy, but if it happens to be at the surface, that bump could give it enough energy to break free. It evaporated!

Notice that you did not have to heat the water to the boiling point. Even if the water is very cold, you will still have molecules at the surface that get bumped hard enough to let them evaporate.

Now, for the next step, fill two glasses half-full of water (or half-empty if you happen to look at things that way.) Put them someplace where they can stay for a few days without being in the way. Cover one with the saucer, and leave the other open.

After a few days, what do you think will happen? The water in the uncovered glass will probably evaporate away, but the water in the covered glass will still be there. Why? Does covering the glass stop the process of evaporation? No. Instead, it increases something else to balance the evaporation. Condensation.

Think back to that molecule of water that was bumped free. It is now bouncing around with the other molecules in the air. If it bounces in the right direction, it could bump back into the surface of the water. If that happens, it can stick, giving up some of its extra energy, and changing back into the liquid form of water.

In the covered glass, the water continues to evaporate just as quickly as it does in the open glass. Because the glass is closed, the number of water molecules in the air increases, meaning more and more of them will bump back into the water, changing back to a liquid. You quickly reach the point where things balance. There are just as many water molecules condensing back to water as there are evaporating into the air. So covering the glass does not stop it from evaporating. Instead, it keeps the water vapor in place, so it can bump back into the liquid again.

Now, thinking about that, why would a windy day make your water evaporate faster? If the air is still, then it is easy for a water molecule to be bumped free, rebound from an air molecule, and rejoin the water. On the other hand, if the air is moving, the water molecule may be moved away from the liquid before it bounces back. The water molecules don't leave any faster. They just have a much smaller chance of bouncing back to the liquid, so the puddle dries up faster.

Have a wonder-filled week.

I love finding things that are so common that we never really think about them, and then finding all the cool science behind them. This week's experiment is one of those. To explore this, you will need:

- a rubber band or a balloon
- a piece of string about a foot long

Lets start with a rubber band. Hold one end in each hand and pull. What do you notice? The rubber band stretches easily, getting longer and thinner. You can probably stretch it to two or three times its original length. Now try the same thing with the piece of string. Does it stretch like the rubber? No. Once it pulls tight that is it. No stretching.

What is different about the rubber that makes it stretch? To answer that, we need to play with the string. This is easier if you have two people, but one person can do it. You want to hold one end of the string, and then start twisting the other end. Keep twisting and twisting. Fairly soon, you should notice that the string starts to kink and twist around itself. Keep twisting.

Once the string has quite a few kinks in it, hold the ends and pull them apart. The string stretches! Move your hands closer together, and the string will kink up again, making it shorter and thicker. As long as the string remains twisted, it will kink and unkink, making it stretchy.

That is exactly what is happening inside the rubber. Rubber is made up of very long, string-like molecules called polymers. Those polymers are twisted and kinked, just as you did with the string. As you pull on the rubber band, you straighten out the kinks in the polymers, just as you did with the twisted piece of string.

OK, one more thing to try. Think about blowing up a balloon. What is the first thing that you do, before you start blowing? You stretch the balloon a couple of times. Why? Why does stretching it make it easier to blow up?

Go back to your string. If you did not pay close attention, you may have to start over and retwist your string. When it is all kinked up, start pulling on the ends, and notice how hard you have to pull to straighten the string. Let the string relax and re-kink. Then stretch it again, noticing any differences.

You should find that the first time you have to pull a little harder to straighten out the string. That is because the kinks are twisted over each other. After stretching and then relaxing, the kinks are more orderly, making it easier to unkink them the next time. The same is true for the rubber in a balloon. The first few stretches make it easier to unkink the polymers.

Have a wonder-filled week.

This week's experiment comes from a question that was sent to me by Hashi, one of the members of the Experiment of the Week list. She noticed that smells were stronger while taking a shower and asked why. To investigate, you will need:

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This week's experiment seems to be a magic trick, but the basic idea is very useful. It is the idea behind the self sealing tires that seal themselves after you run over a nail. To try this, you will need:

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For this week's experiment, we are going to investigate a very important substance which most of us take for granted. Salt. While we hardly think about it as we sprinkle it on our food, in the past, salt was a very important and valuable substance. In addition to enhancing flavor, it is a vital substance in our diet. Before refrigeration, it was a very important way of preserving food.

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When is a glass full of water really full? You may be surprised at how much you can add to a full glass without overflowing the water.

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Why is half a water balloon different from a full one?

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Can you lift an ice cube out of a glass of water with a string? Try it and see.

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Science can be as simple as blowing bubbles in your milk.

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Make a tasty snack while learning about the science of butter.

A simple science trick that is often used in magic shows.

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