My Science School

Look very closely at a piece of thread Do you see the fibres in it? Fibres are the raw materials of fabric.

Many of our clothes are made of plant fibres. Cotton is the most widely used natural fiber. Its fibres come from the seed pods of the cotton plant. A carding machine makes the tangled strands of cotton all lie in the same direction. Then the strands are twisted and stretched to make cotton thread. When it is woven into cloth, cotton is light and cool to wear.

Linen comes from the stem of the flax plant. After the plants are cut, they are soaked in water to loosen the fibres in the stems. Machines then clean the fibres and spin them to make linen thread. Linen is woven into very fine cloth. It is cool to wear, even on a hot day. Silk comes from a caterpillar called a silkworm. It makes silk fibres. It grows by eating leaves from the mulberry tree. Then it spins a cocoon around itself, using one very long strand of fine silk thread. Silk thread is made by twisting the strands of several cocoons together. Pure silk cloth is thin and fine, but very strong.

We get wool from animals. Most wool comes from sheep. The farmers usually shear the sheep once a year. The fibres are straightened to make yarn. Pure wool can be knitted or woven to make warm clothes.

 

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What do you think the first storage containers were made of? They may have been made of animal skins or wood on even stone. But around 8,000 B.C., people learned to dig clay from the ground, mold it into a shape, and let the clay dry out until it was hard. The clay containers worked well for storing dry things. But they were not watertight.

The Chinese discovered how to make clay watertight. If clay is heated to a high enough temperature for a long time, it changes chemically. Clay is made of many different minerals. Dirt and mud have some of these minerals, but not enough for the chemical change needed. The chemical changes make the clay stronger and watertight. Modern pottery ovens, or kilns, use gas, oil, or electricity to get the heat needed. The temperature must be about 1200 °C for 14 to 30 hours. This process is called firing.

In modern factories, the clay is shaped by a machine or in a mold. When the clay has been fired, it is ready for glazing. Glazing means covering the clay with a thin layer of liquid glass. The object is then fired again, and the result is a clay object covered with shiny glass. It is watertight and ready to use.

 

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"Wash your hands," your mum says. As you squeeze the liquid soap into your hands, you wonder, "Where's the dirt?" Some flakes of dirt may be too tiny for you to see. But the soap surrounds, "captures," and breaks up the dirt into smaller bits. Once the dirt is broken up, water can rinse it away.

Soap is made by blending animal or vegetable fat and a very strong chemical called lye. Heating this over a hot fire causes a thick, hot liquid to form. Colourings and fragrances are added. Then the mixture is dried.

A machine slices the dried soap into chunks that look like noodles. To make liquid soap, the soap noodles are blended with water and heated again. To make bar soap, the noodles are shaped into "logs" by another machine. These logs are sliced, like a loaf of bread. The "slices" are pressed into shapes and wrapped-then they are bars of soap!

 

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When the Chinese made paper 2,000 years ago, they used garbage. Rags and old fishing nets, along with plants, were boiled in a huge tub of water. They stirred the mixture and beat it into a pulp. They let the water drain and then pressed the pulp. When it dried, it was a sheet of paper. Try making your own!

You Will Need:

• used paper or newspaper


• leaves and flowers (optional) 480 ml to 960 ml hot water


• a bowl


• a hand whisk or fork


• a baking tray 23 x 33 cm


• a rolling pin


• newspaper


• paper towel


• a paper form (a piece of wire mesh with folded


• edges or window screening in an


• embroidery ring) an old cloth towel


• spray starch

What to do:

1. Tear the used paper and newspapers into pieces about the size of postage stamps.

2. Drop them into the bowl and add hot water. Beat the mixture until it is smooth. There should be no big pieces left. The pulp should be thick, but thin enough to pour, like a porridge.

3. Pour the mixture into the baking pan. Then dip the paper form into the pan, sliding it under the mixture. More the mesh around to get a thick, even layer of mixture on top. You may want to use your fingers to spread the mixture out.

4. Use both hands to lift the paper form straight up out of the pan and let the water drain away. If you like, add a design. Place leaves and flowers on top of the pulp that's on the paper form.

5. Lay the paper form between the pages of a newspaper. Place paper towels on top of the pulp. Then roll a rolling pin over the newspaper to blot water from the pulp.

6. Turn the paper form over onto an old cloth towel. Gently remove your homemade paper from the paper form. Let your paper dry on the towel for a day. Spray starch can be used to help "set" the paper and make it easier to write on.

 

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Paper is one of the greatest inventions, Imagine a world without it. There would be no books, magazines, newspapers, or boxes. How would we send letters to friends or do homework?

People make paper from trees. The logs go to a paper mill, where the bark is removed. The wood is then chopped into small pieces about the size of your fingernail.

The wood chips are cooked in steam and chemicals to make a pulp. Sometimes used paper and rags are added. Then the pulp is washed to remove the chemicals and other unwanted materials.

Machines beat the pulp to separate the wood fibres. Sometimes colouring is added at this stage.

Next, the pulp goes to a paper-making machine. It is poured onto a wire-mesh belt that removes the water. After that, rollers squeeze the paper into sheets and dry it.

Finally, the paper goes through heavy rollers that iron it smooth.

Recycled paper is made using shredded newspapers and other used paper products. It is added to the wood chips during the pulp stage, making up 25 to 50 percent of the paper pulp.

 

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Did you know milk is also a raw material used in making ice cream! You can make ice cream at home. But you'll need a friend to help shake and roll the mixture.

You Will Need:

• a large zip-top bag (4 to 5 litres) a sandwich or small zip-top bag


• (1 litre)


• newspaper


• ice cubes


• 240 ml whole milk or half-and-half


• 240 ml coarse salt


• 1 1/2 tablespoons sugar


• 1/4 teaspoon vanilla extract or


• 1 teaspoon chocolate syrup

What to do:

1. Pour the milk, sugar, and flavouring into the small zip-top bag. Seal. Squish the bag to mix.

2. Pour the ice and salt into the large zip top bag

3. Put the small bag into the large bag, Seal the large bag

4. Wrap the large bag in newspaper. Roll it so that the ends can be twisted like a candy wrapper. Then twist the ends closed.

5. Now shake the newspaper. Twist and roll it around. After about 20 minutes, check the ice cream. It should be ready to eat. If not, repeat steps 2 to 5 by adding extra ice and salt and shaking again.

Why did the milk turn to ice cream so quickly? Because heat is taken from the ingredients as the salt helps to melt the ice.

 

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Mmm! When it’s hot, cheese is stringy and gooey. You know cheese is made with milk. But how does milk get to the cheese?

In a cheese factory, cheese makers pour milk into big tanks. They heat the milk and add something called a “starter” to make the milk turn sour.

Next, they add an enzyme called rennin. The rennin makes the milk thicken and harden. The milk turns into a thick solid called curds and a thin liquid called whey.

 The curds are heated until they are firm and the whey is drained off. Machines salt the curd. It is then cut up and pressed into moulds. Most kinds of cheese are stored at a certain temperature for a period of time. This is called aging. Some kinds of cheese are aged for many months to get just the right flavor. When it has aged, the cheese is sent to the shop.

Add a couple of 2 spoonfuls of lemon juice and sugar to a half cup of whole milk. Stir. Let it stand for one minute. Now stir again. What happened? Did it get thicker?

Lemon juice is an acid. It sours the milk. But it also reacts with the fats in the milk. The milk thickens, just as it does when making cheese. The sugar speeds up this reaction.

How was cheese discovered? There is a legend about an Arab traveller accidentally making the first cheese. The legend says that, over 4,000 years ago, this traveller made a trip across the desert. He used a pouch made from a sheep's stomach to carry milk on the trip. Using animal parts like this was common then.

After a long, hot day, the milk turned into a watery, lumpy mixture. Rennin is found in the stomach of some animals. The desert heat and the rennin made the milk separate into curds and whey. Because the traveller was hungry, he ate the curds and whey and found it delicious.

 

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This bread does not rise very high, but you will see how yeast makes the dough expand. When you slice the bread, you will see the holes made from the gas bubbles.

You Will Need:

• 1 packet active dry yeast (12 ml) 60 ml warm water (like bath water, about


• 29 °C)


• 360 ml whole wheat flour


• 125 ml all-purpose flour 125 ml rolled oats


• 60 ml packed brown sugar


• 1 teaspoon salt


• 2 tablespoons vegetable oil


• 240 ml very warm water


• 1 egg


• a clean dish towel


• a greased bread tin

What to do:

1. Pour the 60 ml warm water into a small bowl. Sprinkles in the yeast. It should foam and bubble.


2. In a large bowl, mix the flours, oats, brown sugar, and salt.


3. Add the egg, oil, and very warm water to the large bowl. Mix.


4. Pour in the dissolved yeast and stir. The batter should be thick and sticky. Let it rest for 20 minutes.


5. Pour the batter into greased bread tin. Cover the tin loosely with a clean towel and place in a warm place, such as on top of the oven, to rise for about 35 minutes.


6. Ask an adult to preheat the oven to 92 °C or its lowest setting. Place the bread in the oven for 20 to 30 minutes. It should rise to twice its original height.


7. Ask an adult to turn up the oven to 175 °C. Bake 25 to 30 minutes until lightly browned.

 

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You can't spread a peanut on your sandwich, but you can spread peanut butter. What happens to peanuts between the field and the lunch table?

First, a machine digs up the peanut plants and shakes off the dirt. Another machine separates the pods, or shells, from the leafy tops. Then the peanuts go to a warehouse, where blowers remove the stems.

Rollers crack open the pods. Inside each pod are one, two, or even three peanut seeds. Another machine gently brushes the skins from seeds. A laser scans for rotten ones.

The remaining seeds are washed and roasted. They go into a grinder with salt, oil, sugar, and other ingredients. The mixture is ground. A conveyor belt moves clean, empty jars along while nozzles squirt peanut butter into the jars. The belt carries the filled jars to the next machine. This machine seals the jars and puts on the caps.

Now the jars are ready to be labelled and shipped.

Today, most foods are canned, frozen, put in jars, or packaged in some other way. These are called processed foods. Food is processed to preserve it, or keep it fresh longer. Processing also makes food easier to use. Peanut butter is a good example.

 

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You know where drinking water comes from, but where does the dirty water go? Down the sewer. Sewer water is filtered to remove solids before it is pumped into lakes and streams. This activity will help you see how water is filtered in nature and in a processing plant. But you must never drink your filtered water. It may look clean but it could still have germs in it.

You Will Need:

• an empty plastic bottle muddy water clean gravel


• a small jar with a mouth big enough to fit around the plastic


• bottle


• scissors


• cotton wool balls


• small, clean pebbles


• clean sand

What to Do:

1. Ask an adult to help you cut off the bottom part of the plastic bottle, about 18 centimetres from the cap.

2. Turn the top part of the bottle upside down and place it in the jar.

3. Push a wad of cotton balls into the neck of the bottle. Put in a layer of small pebbles, then a layer of gravel, then a layer of wet sand.

4. Pour some muddy water onto the sand and watch it drip through into the bottom of the bottle.

5. The water that filters through looks cleaner. What happens when you pour the water through the filter a second time? Does it look cleaner still? It is cleaner. Even so, it is not clean enough to drink. Do NOT drink it.

 

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Thirsty? Turn on the kitchen tap and fill a glass with water. Where does that water come from? Like other raw materials, water goes to a factory before it reaches your home.

When it rains, water seeps through the soil and rock a factory called a waterworks cleans the water for people to use.

First, waterworks pumps water from under the ground or from a river or lake. Then it filters the water. It removes tiny bits of dirt. The filtered water looks clean, but it may contain germs. Small amounts of chemicals are added to kill the germs.

The treated water flows to a pumping station sends the water to underground pipes called water mains. When you turn on the tap, water comes from the water main into your house.

Some cities pump treated water into water towers. These are called holding tanks. When water is needed, it flows to water mains on your street.

 

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A radio controlled clock has a radio inside, which receives a signal that comes from a place where an atomic clock is located. Such a clock may be synchronized to the time sent by a single transmitter, such as many national or regional time transmitters, or may use the multiple transmitters used by satellite navigation systems such as GPS. Such systems may be used to automatically set clocks or for any purpose where accurate time is needed. RC clocks may include any feature available for a clock, such as alarm function, display of ambient temperature and humidity, broadcast radio reception, etc.

One common style of radio-controlled clock uses time signals transmitted by dedicated terrestrial longwave radio transmitters, which emit a time code that can be demodulated and displayed by the radio controlled clock. The radio controlled clock will contain an accurate time base oscillator to maintain timekeeping if the radio signal is momentarily unavailable. Other radio controlled clocks use the time signals transmitted by dedicated transmitters in the shortwave bands. Systems using dedicated time signal stations can achieve accuracy of a few tens of milliseconds.

 

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The Internet is a network of computers and certain other devices. In a network, all of the devices are connected. The Internet links tens of thousands of smaller networks. The Internet connects millions of computers in homes, businesses, and schools. People can bank, shop, watch TV, and do many other things on the Internet.

People can also send personal messages through the Internet. Such messages include e-mail (electronic mail), which is sent to and from an electronic “address.” Instant messages, or IM’s, work like back-and-forth conversations.

Many devices can access, or get into, the Internet. They include computers, mobile phones, and electronic game machines. A piece of equipment called a modem connects some devices to the Internet. Other devices can connect by using wireless technology, such as Wi-Fi or Bluetooth. Wireless technology allows communication between devices by means of radio waves sent through the air.

Information on the Internet exists as digital codes. Computers and other devices translate these codes into text, pictures, sounds, and videos. Digital codes are split up into smaller pieces called packets. The packets travel separately through the Internet. When the packets reach a computer or other device they are put back together into a single code. All these bits of information make up pages on the World Wide Web, the system of computer files on the Internet where much information is stored.

 

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The moon is a satellite. It moves on a set path called an orbit around the earth. Anything that travels around a planet is a satellite. Rockets carry artificial satellites into space. They circle high above the earth.

While artificial satellites circle the earth, they pick up radio waves from transmitting stations on the earth. Solar panels on the satellites collect sunlight to make electricity. They use this electricity to send the radio waves back to receiving stations. The receiving stations are often thousands of kilometres away from the transmitting stations.

Today, many hundreds of satellites whirl around the earth. Each one makes life easier for people on the ground.

 

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You're walking down the street when you suddenly hear your favourite song start to play. But where is the music coming from? As you look around, you notice that the person walking ahead of you is searching through his pockets. Of course the song is his special signal, letting him know that he has a call or a message on his mobile phone.

A mobile phone rings, vibrates, or plays music when it receives a signal. A display shows the phone number of the caller and possibly a message, too.

Some people carry mobile phones in their purses, briefcases, or pockets. Mobile phones use radio signals to carry their messages.

The service area for mobile phones is divided into groups called cells. Each cell has a radio transmitter. Signals are sent to the cell where the person using the mobile phone is. People who move around a lot still get their signals. The signals bounce from the transmitter in one cell to the transmitter in the next cell. This happens very quickly. Even if people are on a train while they are talking on a mobile phone, their conversation is not interrupted.

 

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