My Science School

Matter is everything around you. Atoms and compounds are all made of very small parts of matter. Those atoms go on to build the things you see and touch every day. Matter is defined as anything that has mass and takes up space (it has volume).

Everything is made of matter. Matter is anything that has weight and takes up space, so a rock, a dandelion, a rabbit, and a puddle of water are all matter. And you are matter, too. There is matter in everything around you.

Even air is matter. You don’t feel how much air weighs because most things are heavier than air. But air has weight. And it takes up space. You feel it take up space when you breathe. You see it take up space when you blow up a balloon.

Even though matter is everywhere around the universe, it usually only comes in just a few forms. Scientists have discovered five states of matter so far: solid, liquid, gas, plasma, and Bose-Einstein condensates. The most common are solids, liquids, and gases.

What’s the difference between these different states of matter? It’s all about the physical state of their atoms and molecules.

For example, a water molecule (H2O) consists of two hydrogen (H) atoms and one oxygen (O) atom. Whether its physical state is a solid (ice), a liquid (water), or a gas (vapor), it’s still water made up of H2O molecules.

What is in a sand castle? Millions and millions of tiny grains of sand. The many grains of sand are packed together to make a single shape, like a castle with towers, walls, and bridges.

And what are you made of? Millions and millions of tiny bits, each one even smaller than a grain of sand. You and everything around you - people and animals, cars, rocks, water, and even the air - are made of tiny bits that are put together in different ways.

These bits are called atoms. Atoms are much smaller than a grain of sand. In fact, they are so small that you can’t see them. But if you could see them, you would find that these tiny atoms are made up of even smaller pieces. Even though atoms are so small that you can’t see them, they still have weight, and they take up space. They are tiny bits of matter. Everything that is matter - even you - is made up of tiny atoms.

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Imagine floating through the air or standing on the ceiling. An astronaut orbiting, or circling, the earth in a spacecraft can do both because of something called weightlessness.

Orbiting the earth is really a lot like falling in space. If you threw a stone from a very high mountain, it would curve down gently before it hit the ground. The harder you threw the stone, the further it would go. The surface of the earth is curved. What if you could throw a stone so hard that the curve as it fell was exactly the same as the curve of the earth? The stone wouldn’t hit the ground - it would go into orbit. In other words, it would become a satellite of the earth.

A spacecraft “falls” around the earth in the same way. This constant falling makes everything inside the spacecraft seem like it has no weight at all.

What happens then? The astronauts float, unless they hang on to something! Anything they “drop” floats in the air when they let go of it. And if they jump, they don’t come down. They hit their heads on the ceiling instead.

Far out in space, a satellite circles the earth. What keeps it from crashing into the earth? And what keeps it from sailing away into space?

Two kinds of forces work to make the satellite circle the earth. One is the tremendous push of the satellite’s speed - thousands of kilometres per hour. Without this push, gravity would pull the satellite back to the earth.

The other force is the pull of the earth’s gravity, which reaches far out into space. Without this pull, a satellite would travel in a straight line, away from the earth.

Gravity pulls the satellite towards the earth. But the speed of the satellite pushes it outwards. When the push and the pull are even, the satellite can’t sail away from the earth - or fall back to the earth, either. Instead, it speeds around the earth, making a circle in space.

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Aeroplane wings have a special shape. They are curved on top and straight on the bottom. This shape is what helps lift the plane up.

When the plane starts to move, the wings cut through the air. The air moves over the curved top of the wing and under the straight bottom. The air moving over each wing pushes down on it. And the air moving under each wing pushes up.

Since the curved top of the wing is longer than the straight bottom, air moving above the wing travels further than air moving below it. So air going above the wing moves faster. The faster it moves, the less it pushes. As the push over the wing gets weaker, the stronger push under the wing begins to lift the plane. So the plane leaves the ground. As long as the plane keeps moving forward, the wings lift it and help it to fly.

Different wing shapes help aeroplanes fly in different ways. Planes that fly at both low speeds and high speeds have wings that stick straight out from the body of the plane. Wings that sweep backward - like the wings of the Stealth plane - help a plane to fly better at very high speeds.

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Imagine a restaurant with a swinging door leading to the kitchen. Two waiters try to push the door open from opposite sides at the same time. One holds a huge bowl of spaghetti. The other balances a tray of dishes. If they both push with the same force, the door doesn’t move. But if the waiter with the spaghetti does not push as hard as the other waiter, the door swings open. And crash - spaghetti flies everywhere!

When equal forces push on an object from opposite sides, that object is in equilibrium. An object that is in equilibrium is balanced. It won’t move or tip over unless an extra push is added from one direction.

A force called gravity pulls all objects downwards, towards the centre of the earth. Every object has its own centre of gravity, the spot where it can be balanced. If you support an object at its centre of gravity, it will be in equilibrium.

Ask a grown-up to help you carefully stick a small fork into a small potato, with the top side of the fork facing upwards. Next, find a pencil that is longer than the fork.

Push the pencil into the other side of the potato until about 2.5 centimetres sticks out above the fork. Balance the pencil tip on the edge of a table, with the fork extending below the table. The potato stays balanced because its centre of gravity is actually in the pencil tip!

Magnets can do some strange things. That’s what makes them such fun to play with. They can stick to each other. They can make nails or pins hang onto each other. They can even “lead” each other across a piece of glass. A magnet on top of the glass follows a magnet you slide along under the glass.

A special force, or pull, makes a magnet work. The pull is strongest in two places called poles - a north pole and a south pole.

Both poles of a magnet will hang onto iron and steel things, like pans and pins. And either pole will hang onto one pole of another magnet. The north pole of one magnet and the south pole of the other will pull on each other, and the magnets will stick together like best friends.

But magnets stick together only if the poles don’t match. If you put two north poles or two south poles together, the magnets try to push each other away!

See for yourself how things get magnetic power by making your own magnet. Touch a large metal paper clip to a small metal paper clip. What happens? Straighten one end of the large paper clip. Then stroke one end of a magnet down the length of the straightened part 50 times. Always use only one pole of the magnet and always stroke in the same direction. Touch the large paper clip to the small paper clip again. Now what happens?

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You might have often heard the term aurora borealis but what is an aurora?

An aurora is nothing but beautiful light shows in the sky. One can witness them near the North and the South Pole. If you witness it at the North Pole, it is aurora borealis or northern lights. In the South Pole, it is called aurora australis or the southern lights.

The Sun's role

Now, even though auroras are best seen at night. they are actually caused by the Sun. Here's how: The Sun sends to Earth heat light and lots of energy and other small particles. (But the Sun doesn't always send the same amount of energy towards Earth.) Since the Earth is surrounded by a protective magnetic field, we do not experience the presence of most of these energy and small particles. Constantly streaming solar wind and solar storms are also sent by the Sun out into the space. During one such type of solar storm called a coronal mass ejection, the Sun sends out a huge bubble of electrified gas that can travel through space at high speeds. When this solar storm charges towards Earth, some of the energy can penetrate the magnetic field lines at the North and South Poles and enter the Earth's atmosphere.

Electrically charged particles interact with the gases in the Earth's atmosphere and result in beautiful displays of light in the sky.

Of green, blue and purple

If you have noticed an aurora or seen its photographs the colours in the sky are usually green, red, purple and blue. This is because the oxygen in our atmosphere gives off green and red light when mixed with the energy particles, and nitrogen glows blue and purple.

 

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Dr. Mothbold’s automatic polka-dotting machine can paint polka dots on anything - shirts, socks, pancakes, and even pretzels!

Best of all, the polka-dotter is a perpetual motion machine. Perpetual motion is motion, or movement, that goes on forever.

All the parts of the polka-dotter create forces that make the other parts work. As each part gets a push or pull, it gives a push or pull to another part. So, says Dr. Mothbold proudly, this machine will never stop! Is the doctor right?

No. Although pushes and pulls will keep the machine going for a while, other things will make it slow down. Friction is one of these things. The rubbing of wheels against the belt, the brushes rubbing as they paint and the bumping of the brushes on the paint lever will slow down the machine. Finally, the automatic polka-dotter will stop.

People have tried to make all kinds of perpetual motion machines. But the friction that slows the machines is always a little stronger than the forces the machines make to keep running. That is why perpetual motion does not work.

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The light turns green, and the car starts to move quickly. You feel as if a big, invisible hand pushes you back in the car seat. When the car stops quickly, the same “hand” seems to push you forwards.

What is this invisible “something” that pushes you when a car starts and stops? It’s called inertia.

Inertia is the name for the way things resist a change in movement. When something is stopped, it stays stopped. It starts to move only when a force - a push or a pull - makes it move. And when something is moving, it tries to keep moving. It won’t stop until a force stops it.

When a car starts to move, your body tries to stay stopped. So you feel yourself pressing back as the car seat moves forwards. And when the car stops, your body tries to keep moving. Inertia “pushes” you forwards. Your seat belt is there to hold you back.

Use a whirling egg to see the force of inertia. Let a fresh egg warm up to room temperature. Then place the egg in a bowl. Gently spin the egg by pushing it with your finger. Stop the egg from spinning by touching it lightly on the top. Then quickly lift your finger from the egg. What happens?

The egg starts spinning again. Why? When you start the egg spinning, the liquid inside the shell spins, too. When you stop the egg, inertia makes the liquid inside keep spinning. When you let go of the egg, the spinning liquid makes the egg start spinning again.

There’s a big branch on the pavement. Slow down your bike! Then you can go around the branch safely.

Your bike has brakes to help it stop. When you squeeze the levers on the handlebars, the brake pads rub against the wheels and stop them from turning. The rubbing that stops the wheels is called friction.

Friction happens because all things have a rough surface. Even things that look shiny and polished have very tiny areas that are not smooth. When one object slides across another, the rough spots rub against one another. This rubbing, or friction, makes things move more and more slowly, until finally they stop.

Friction is useful when it helps you stop your bike. But sometimes we want things to keep moving smoothly. Then we need to lessen friction. We can do this with a slippery substance, such as oil or grease. For example, the grease on your bicycle chain lessens friction so that you can pedal easily and smoothly.

Suppose someone asked you to lift a hippopotamus! It sounds impossible, but with a simple machine called a pulley, you could do it.

A pulley is a special kind of wheel and axle. A rope or steel cable fits around the rim of the wheel. When one end of the rope is pulled down, the rope slides over the wheel, which turns on the axle. Then the load at the other end moves up.

With one pulley, the load moves up as far as you pull the rope down. You work just as hard to pull the rope as you would to pick up the load, but you can pull in a direction that is easier for you.

With two pulleys, you can make lifting even easier. The second pulley is attached to the thing you lift. Each part of the rope between the pulleys holds half the weight, so you pull only half as hard to move the load. But the load is held up by twice as much rope. So you will have to pull the rope twice as far as the distance you want the load to move.

The more pulleys you use, the easier it is to lift a load. But you will have to pull more and more rope. You might be able to lift that hippopotamus with a great number of pulleys, but you will have to pull a lot of rope!

Wheels don’t eat. But some wheels use teeth to help them do work, work that other wheels can’t do.

A wheel with teeth is called a gear. It is a wheel that makes other wheels move. If you look at an eggbeater, you can see three gears. The big one with the handle is the gear you turn. The teeth on this gear fit into the spaces between the teeth on the two smaller gears. When you turn the handle, the teeth on the big gear push against the teeth on the small gears and make these gears turn. One turn of the big gear makes the small gears turn many times. So the beater blades move very quickly.

First, second, third, fourth - these are the different-sized gears that fit together in a car. The engine turns a set of gears connected to a rod called a crankshaft. The crankshaft turns the axle and the wheels. The lowest gear is first gear. It allows the crankshaft to turn much more quickly than the wheels. This makes more power for starting and for climbing steep hills. Fourth gear allows the wheels to travel around more quickly while using less power. Fourth gear is used for cruising along at the same speed without stopping and starting. It’s the gear that is used on a motorway.

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