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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Make a diver that will rise and fall at your command, if you know the science.

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What is matter?

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Straw Trombone

Science with music.

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Sand Angles

Learn structural engineering by making piles of candy.

This week's experiment is a combination of two past experiments. We are going to combine the idea of the Dancing Raisins with the Cartesian Diver. You will need:

- a bottle of clear, carbonated soda. It needs to have a screw on cap.
- raisins

First, if the bottle of soda has a label, remove it so you can see inside. Carefully remove the cap. Drop in 5 or 6 raisins and quickly put the cap on tightly. Watch the raisins. They should sink to the bottom, with lots of tiny bubbles rising from them. After a few seconds, one or more of them will probably begin to rise. As soon as a raisin begins to rise, give the bottle a good, hard squeeze. As you do that, you should see the raisin begin to sink again. Release the pressure and the raisin begins to rise again.

Why does it do that? Lets take it one part at a time, starting with the bubbles. Where are the bubbles coming from? From the soda, right? The soda has carbon dioxide gas dissolved in it. This gas escapes, forming bubbles.

OK, so why do more bubbles form on the raisins? When you drop the raisin into the soda, its wrinkled skin traps lots of tiny air bubbles. These bubbles act as a starting point for more bubbles. As carbon dioxide gas moves from the soda to the bubbles, they get larger and larger. When they get large enough, the raisin begins to float.

Why does the raisin float? For that matter, why does anything float? If something weighs less than the same volume of water, it will float. For example, a cubic foot of Styrofoam weighs less than a cubic foot of water, so it floats. A cubic foot of steel weighs more than a cubic foot of water, so it sinks. The raisin is denser than the water, so it sinks. When the bubbles form, the combination of raisin and air weigh less than the same volume of water, so they begin to float.

OK, so far, so good. If you don't disturb things, the raisin will rise to the surface, where some of the bubbles will probably pop, letting the raisin sink again. But what happened when you squeezed the bottle? Why did the raisins sink? At first, you might think that you shook enough bubbles loose to let it sink again, but as soon as you stopped squeezing, it began to rise again.

So what would squeezing do? Squeezing the bottle makes it smaller, which means that the stuff inside has to get smaller. You can't make water smaller by squeezing it, so that means the air inside the bottle gets smaller. If you watch the top of the bottle, you can see the air space at the top getting smaller. The bubbles also get smaller. The smaller bubbles still weigh the same, since they contain the same amount of air, just squeezed into a smaller space. That makes them denser, letting the raisin sink. That is the idea behind the classic science experiment called the Cartesian Diver, which is the reason I called this experiment the Cartesian Raisins.

After a short time, you will notice that the raisins stop rising. Now what is wrong? Nothing. As the pressure builds up inside the bottle, the bubbles stop forming. All you need to do to get things going again is loosen the top. As soon as you hear the hiss of escaping air, you will see a burst of bubbles and some of the raisins will almost shoot to the surface. Tighten the cap and you will have another minute or two to play with the Cartesian Raisins.

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Specific Heat

Is a tile floor really cooler than the carpet?

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States of Matter

Solids, liquids, gases, and plasma too.

How many cotton balls can you fit into a full glass of water?

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