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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I first became interested in rock stacking during our trip to Technorama, the Swiss Science Center. Thorsten Künnemann, their Executive Director took us on a marvelous tour of Zurich. As we walked along the shore of Lake Zurich, we came to an area that was filled with amazing stacks of balanced rocks. When you first see them, you think that they must be held together with glue or mud. Only when you get very close can you see that it is all a matter of balance. Since then, we have seen similar stacks in other places and made some of our own.

If you would like to try rock stacking, you will need:

• a flat, stable surface
• a variety of rocks or other things to stack
• steady hands
• lots of patience

While at first rock stacking may seem like a frivolous activity, there is actually quite a bit of science and engineering involved. As we saw in the Science of Balance video, we can balance an object by keeping its center of gravity (its balancing point) directly above its base (the part of the object that is supporting it.)

To start, you need a wide variety of rocks, or other objects to stack. If you don't have lots of large rocks, you might try stacking toys, stuffed animals, or other irregularly shaped objects that are not breakable.

Select a large, steady rock as your foundation. You want the rock on the bottom to be very stable, because if it wobbles, your entire stack will wobble, which usually means that it all falls down. By using a wide, flat rock, it has a large base, which gives you plenty of working room to keep the center of gravity inside that base. While you are learning the art of rock stacking, you will have better success if you also choose a foundation rock that has a fairly flat top, to make it easier to balance the next rock.

It is easiest if you start simply, using fairly flat rocks to make stacking easier. Keep in mind that as you add each rock, you are adding pressure to the rocks under it, which may shift their center of gravity. Work slowly. Instead of putting a stone in place and releasing it, gradually let its weight rest on the stack, checking to see whether the stack remains stable.

Once you have the knack of stacking flat rocks, then you can start to get more creative and adventurous. Use rocks with unusual shapes, and try balancing them on smaller bases. Remember that a smaller base means you have to be more careful with the stack's center of gravity. Also remember that each rock can change the center of gravity of the entire stack, throwing the stones below it out of balance. If one orientation is unstable, try turning the rock to a different side. If that does not work, then try a different stone. The more you practice; the more you will learn about the art and science of stacking rocks.

At some time in your life, you have probably heard that in a fall, cats always land on their feet. Is that true? Well, usually it is. Cats have the amazing ability to turn themselves right side up as they are falling. That does not mean that a fall will not injure them. If you fell off a tall building, would landing on your feet keep you from being injured? No. The same is true for cats. Landing on their feet lets their legs flex to absorb some of the impact, and keeps the impact from directly hitting more delicate bones, but cats do not have any magical protection against injury from falling.

What is amazing is the way that they perform this trick of landing on their feet. They do it by combining fast reflexes with the laws of physics. To get an idea of how they do it, you will need:

• a chair that swivels easily. Common office chairs work very well for this.
• an open area with plenty of room, so you don't break any lamps, furniture, or legs.

OK, lets start by thinking about what the cat has to accomplish. It is falling, which means that it does not have anything to push or pull on to turn itself. Instead of falling, you can get an idea of the problem that they face by sitting in the swivel chair. Make sure that you have plenty of open space around you by holding your feet straight out and turning in a complete circle. You want at least a foot or two of open space between your feet and the closest thing you could bump into.

Now lets get an idea of the challenge the cat faces. Sit cross legged in the chair, so your feet do not stick out. Put your arms in your lap, with your elbows tucked in against your side. Your challenge is to turn the chair around so that you are facing the opposite direction by twisting your body from side to side. Don't move your arms or legs. You can twist at the waist and your neck, but nothing else. DON'T HURT YOURSELF! You will find that you can turn the chair slightly to the right by twisting your body to the left. The problem is that when you twist back to the right, the chair spins back to the left, winding up back where it started. Wiggling the chair back and forth is no problem, but you don't get very far towards turning the chair around.

To see how the cat manages its trick, lets try something different. Keep your elbows at your side, but extend your hands out to the side. Then try twisting again. This time you will notice that the same motions cause you to swivel back and forth farther. Extend your arms all the way out, and try it again. Now, you are really moving back and forth. As you move your arms further and farther from your body, you can use their inertia (resistance to changes in motion) to push against.

You still have the problem that you are twisting back and forth. Remember that you are a falling cat, and you need to turn yourself so you can land on your feet. That leads us to your next step.

Extend your arms all the way out, and then twist to your left. That swivels the chair and your body to the right. Now, before you twist the other direction, pull your arms back in close to your body. Since your arms are in close, you can turn back without swiveling the chair back in the other direction. You have turned part of the way around, and you are back into the position to do it again. Extend your arms again, and repeat the process. It took me three arm swings to turn my chair around so that I was facing in the opposite direction.

Cats do this maneuver even better because they are incredibly flexible. They extend their front legs while pulling in their back legs, and then twist in the direction they want to turn. Very quickly, they pull in their front legs, and extend their back legs, making another quick twist that lets them wind up facing as much as 180° from their original direction.

Although cats are incredibly fast at this, it still takes time. Cats that fall from a very short distance do not have enough time to twist around. Also remember that landing on their feet does not mean that they don't get hurt during a fall. Their reflexes and flexibility can help them land in the best position, but they can still suffer injuries and broken bones from a fall; so you should not use your cat as an experimental subject.

If you want to experiment further, try holding a weight in each hand as you do the experiment. Do you think that will make it work better or worse? Try experimenting with different arm motions. I had interesting results from making the same motions that you would use for paddling a canoe.

Link to Sunglass Science: Polarized Light

This time we will explore things that are usually invisible, revealing new things about the world around us.

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Link to Whistle Stick, part 1

I hope that you made your own Whistle Stick, and have been playing...., I mean experimenting with it. I also hope that you spent some time thinking about the science behind the sound that it makes, because that is what we are going to explore this time. For your exploration, you will need:

- a wooden spoon
- a large container of water
- the Whistle Stick from last week

It's always good to start with the basics, so begin by thinking about sounds in general. We hear a sound because of waves traveling through the air. Just as dropping a stone into a pond causes waves to spread out across the water, popping a balloon, vibrating a guitar string, or singing a song causes waves to spread through the air. When those waves hit our ear drums, we hear the sound. That means that the Whistle Stick must be producing waves in the air. But how? That is where the wooden spoon comes in. We will use it in place of the popsicle stick, and look at waves in water instead of air. Hold the wooden spoon between your palms, with the end of the spoon in a container of water.
Slide your palms to twirl the spoon slowly in the water. As the spoon spins, it makes waves in the water. Try spinning it at different speeds, noticing how that changes the distance between the waves. What you should notice is that as the spoon twirls, it pushes on the water to send out a wave. As you spin the spoon faster and faster, it makes more waves, and those waves get closer and closer together.
Now lets think about sound waves. The picture at the right shows a graph of the sound produced by the whistle stick. Notice that at the start of the sound, it reaches far up graph. The higher up the graph it goes, the closer together the sound waves are, and the higher the pitch of the sound. If you click the picture, you can watch a short video, letting you hear the sound, seeing how the changing sound matches the graph.
It is much easier to see (and hear) if we slow things down. This graph shows the same sound, stretched out four times longer than the original. That lets us see the curve as the pitch falls. Again, you can click the picture to watch a short video. Because it plays the sound slower, it is easier to see (and hear) that the sound begins with a high pitch (waves very close together), and then the pitch falls as the waves get farther apart.

Now lets put that all together. Like the wooden spoon, the faster the popsicle stick spins, the closer together the waves will be, and the higher the pitch of its sound. When you first snap your fingers, the Whistle Stick spins very fast, making a high pitched sound. As it pushes against the air to produce those waves, it gives up some of its energy of motion. That causes it to spin slower, producing a lower pitched sound. Looking at the graph, we can see that the rate of spin slows very quickly at first, and then more gradually.

If you remember from last week, I also made a Whistle Stick from a tongue depressor that was much wider. it made a much lower pitched sound, that did not last nearly as long. Why? The wider blade had to push against more air, transferring the energy of motion much faster, causing the speed of its spinning to drop much faster.

If you want to do some experimenting, you might try cutting notches into the sides of the stick or doing other things to change its shape. Do you think that would change the sound? Sounds like a good reason to eat more popsicles to me.

Link to Sunglass Science: Birefringence Light

Grab your shades for a different way of seeing the world around you.

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This week's experiment is a trick that my Grandfather taught me when I was very young. He called it a "whistle stick", and making one brought back delightful memories from my childhood. This experiment requires the use of a sharp knife, so if you are young, you may need adult assistance. It is not difficult, but even adults should keep safety in mind. To try this you will need:

- a popsicle stick (with the popsicle removed) - a sharp knife with a short blade - a pencil or pen Making a Whistle Stick requires some whittling, the art of using a knife to shave thin slivers from a piece of wood. During my Grandfather's time, whittling was a common pass time, sometimes for carving interesting things, and sometimes just to give your hands something to do while you were thinking. While there are specialized knives for wood carving, most sharp pocket knives can be used for whittling. A dull knife will not work well, making it much harder to shape the wood, and much more likely that you will cut your finger instead.
The first thing to do is to eat the popsicle so you can get at the stick. Of course you can buy popsicle sticks from a craft or hobby store, but what is the fun in that? Once all of the icy treat has been removed from the stick, we will use the pencil to mark the parts that we want to remove. Starting about an inch from one end, draw lines from each side that come inwards towards the end, as seen in the photograph.
Now comes the part where you have to be careful and patient. We are going to whittle away the wood that is outside those lines. Hold the piece of wood in your left hand (if you are right handed), and with the marked end pointing away from you. Holding the knife in your right hand, with the sharp edge pointing away from you as in the photo above. Always cut away from you, never towards your hand. You want to cut away very thin slivers of wood. Trying to cut too thick a slice will split the stick. Once you get the stick close to the right shape, start cutting even smaller slivers, shaping and rounding the end. Don't worry if you make a mistake along the way. You can always eat another popsicle to get another stick.
Your Whistle Stick is now complete. To use it, press your finger and thumb together, as if you were going to snap your fingers. You can use either your first finger or your middle finger. Place the whittled end of the Whistle Stick in between finger and thumb. Then snap your finger. The Whistle Stick should fly away, making a strange, whistling sound. You may have to practice a few times, and the video should help with how to hold it and what to expect. At the end of the video, I try the same thing with a tongue depressor which is quite a bit wider than the popsicle stick. Notice the difference in the sound.

Once you have played with the Whistle Stick a bit, then it is time to do some scientific thinking. Why does it make that sound? Why does the tongue depressor make a different sound? Listening to the two, you should be able to figure out what is happening. Give it some thought, and some experimentation (which may mean that you need more popsicle sticks), and we will look into that deeper next time.

Have a wonder-filled week!

Link to Whistle Stick, part 2

Three Holes, part 2

Hopefully, you spent quite a bit of time thinking about last week's experiment, and more importantly, performing the experiment to see if you were correct. If not, before you read any more, GO TRY IT! If you don't, you are missing out on the actual fun of scientific investigation. This week, you will need:

- the same materials that we used in part 1.
- 3 more bottles
- some wooden blocks or other things to change the height of the bottles

If you did try it, you probably got results similar to what you see in the photo below.

If you did try it, you found that the water stream from the middle hole hit at the greatest distance from the bottle. Why? To understand that, we need to look at the variables involved with each of the three streams.

Variable? What is that? It is something that can change from one test to another. If we think of the three holes as three different tests, then the variables are the things that change from one to another.

The first variable is the water pressure, and that varies according to the depth of the water. The deeper the water, the greater the pressure. That means that the top hole will have the least water pressure, and the bottom hole will have the greatest water pressure. Then why didn't the bottom stream go the farthest? Because there is another variable involved.

What else is different for each stream, besides the water pressure? The distance that they have to fall to hit the surface! If that distance is too short, the stream when it could still travel much further from the bottle. The top stream has a longer distance to fall, giving it a longer time to move away from the bottle. The bottom stream has the shortest distance to fall, so it has the least time to move away from the bottle.

Looking at the three streams, the bottom one has the most water pressure, but not very far to fall before it hits the surface. The top stream has the least water pressure, but a long way to go before it hits. The middle stream has more pressure than the top, and more distance to fall than the bottom. That combination lets it hit the farthest from the bottle.

Is there a way that we can compare those variables? Easy! All we have to do is to control one of those variables.

Which will go farther?

You could control the water pressure by using three bottles that each had a hole at the same depth. By placing the bottles on top of blocks, you could arrange them so that the three streams were at different heights. With the same pressure for each, the highest stream would go farther, since it has the longest time to travel away from the bottle before it hits the surface.

Which will go farther this time?

You could control the distance the water has to fall by using three bottles again, but this time, make a hole near the bottom of one, near the middle of the second, and near the top of the third. Then place them on blocks so that the three streams are all the same distance from the surface. This time, the stream with the most water pressure (nearest the bottom of the bottle) will go farther.

From there, you can gradually change the height of the blocks until all three bottles were the same height. That would bring you back to where we started, with the middle stream reaching the farthest. With careful testing, you would probably find that the maximum distance would not be at exactly the middle of the bottle, since one variable may make a larger difference than the other. If one is causing more difference, which do you think it is? You'll have to try it yourself to find out.

Have a wonder-filled week.

Three Holes
This week's experiment will give you some good practice at thinking scientifically. The experiment itself is very simple, but as with many simple things, the more you think about it, the more you will see. To try this, you will need: - a two liter soft drink bottle - pliers - a sharp nail - water First you need to empty the two liter bottle. I highly recommend using the soda to experiment with making the perfect ice cream float. Once the bottle is empty, rinse it and remove the plastic label if it has one.
We want to make three holes in the plastic bottle, each at a different depth. Holding the nail with the pliers, make a small hole about one inch up from the bottom of the bottle. I found that twisting the nail back and forth as you push makes it easier to start the hole. You want the hole to be round and as smooth as possible. Be careful not to tear the plastic (or your skin!) Once you make the hole, wiggle the nail around a bit to help make the hole round.
After you make the first hole, make the second about half way up the bottle, and slightly to one side. You want all three holes to be as close to the same size as possible, and you do not want the holes to be directly above each other. The third hole should be about an inch or so below the point where the top of the bottle starts to narrow, and again a little to one side. The photo on the right shows approximate locations.
Place the bottle in the sink, under the faucet. Fill the bottle with water, and leave the water flowing just enough to keep the bottle full as the water flows out of the three holes. We want to compare how far each stream of water goes, which is why we did not want one hole directly above another. We want to be able to see the three streams easily. Now you should understand why we are working in the sink, to keep from making a mess.

Before you actually try this experiment, take some time to think about it. Once the bottle is full, water will be flowing out of all three holes. If you measured how far each stream of water moved away from the bottle before it hit the bottom of the sink, which stream of water would hit the farthest away? Which stream would hit the closest? Why? Keep in mind that there may be more than one thing to consider in how far the water reaches.

Once you have spent enough time thinking to have a good idea of what will happen, turn on the water and try it yourself. Next week, we will look at the results, and figure out why it worked the way it did.

Have a wonder-filled week!

Go to Part 2.

Link to Part 1

Link to Part 2

The answer to Part 2, and a fun "science trick."

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Well, last time I left you with a challenge. If you have two metal rods (straightened paper clips) and one of them is magnetized, how to you find out which is which, without using anything else? To find out, you will need:

- steel wool
- a sheet of paper
- the two paper clips we used last time (or you can make two new ones)

I know that I said you could not use anything else. The steel wool is for later, to help explain what is happening. Pick up the two paper clips and bring the ends together. They should stick if they are still magnetized. OK, so which one is the magnet? To find out, we need to do something different. Bring the end of one paper clip near the middle of the other paper clip. Does it stick? If it does, then it is the magnetized clip. If it does not, then bring one end of the other paper clip to the middle of that one. The magnetized clip will stick to the middle of the nonmagnetized clip. The nonmagnetized clip will NOT stick to the middle of the magnetized one. Why?

Place the magnetized clip on a sheet of paper. Hold the steel wool over the clip, grab the two ends of the wad of steel wool and rub them against each other. Tiny bits of steel wool should fall onto the paper, and you should notice that they are sticking to the paper clip. Pay close attention to where on the paper clip they stick. The ends, right? That is where the magnetic pole is, and it is where the magnetic field is strongest. The middle of the paper clip has almost no magnetic field at all, so the steel wool does not stick there.

Now you know why the nonmagnetized clip would not stick to the middle of the magnetized clip. The magnetic field in the middle was not strong enough to attract it. On the other hand, the end of the magnetized clip will stick to any part of the nonmagnetized clip.

Not at all hard to figure out, once you know the science.