My Science School

Coal is a porous, black carbon-rich, naturally-occurring material which is mined from the earth. It is formed by the decomposition of remains of plants which died millions of years ago. Though rich in carbon, coal contains a lot of impurities including sulpher. When used as a fuel it poisons the air with sulphur dioxide.

Charcoal is a black, porous material obtained by heating wood in a closed space, with no air. This type of charcoal contains mostly carbon. Another type is made by heating bones.

Charcoal is used as a filter to clean gases and liquids and as a fuel. It is also as a drawing instrument.

 

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The blood takes oxygen to each and every part of the body but the oxygen is not in gaseous form. It is dissolved in the blood. If air is injected directly into a vein or artery, say through an injection, the air will not easily get dissolved and will travel in the bloodstream in the form of a bubble. This bubble may finally reach the brain and get lodged in a blood vessel disrupting the flow of blood in the brain. This can lead to serious complications, even death.

It is to avoid the possibility of introducing an air bubble in the bloodstream that the doctor expels a little liquid from syringe. If air is trapped in the needle it will be driven out by the liquid.

 

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After a nuclear explosion has occurred, harmful radioactive material is released into the atmosphere. The debris in due course descends to the surface of the earth and pollutes whatever material it comes in contact with.

This debris, called ‘fallout’ is produced by all nuclear bombs – atom bomb or hydrogen bomb – even if they have been exploded for peaceful purposes. The debris once released into the atmosphere is carried by winds around the world and slowly brought down to the earth either by gravity or by rainfall. The fallout that occurs immediately after an explosion is highly radioactive and will kill living things located near the blast site. The delayed fallout may occur after a few weeks or a number of years. This causes long-term radiation damage to all living things: plants, animals and humans over a vast area. Some of the fallout elements may get into the bodies of living organisms.

The Pokhran explosions were done underground by Indian scientists to keep the fallout to a minimum.

 

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Electricity resulting from the application of mechanical pressure on certain crystals like quartz and tourmaline is called piezoelectricity.

When these crystals are subjected to mechanical strain, a voltage across their opposite faces.

Conversely when a voltage is applied to such crystals, they vibrate.

Piezoelectric materials are used for converting mechanical strain into an electrical signal in such devices as microphones and phonograph pick-ups. The converse effect in which a mechanical output is derived from an electrical signal output is used in such devices as headphones and quartz watches.

The phenomenon of piezoelectricity was discovered in the 1880s.

 

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When reading the printed matter on the wrapper of a bar of toilet soap, I saw the following: TFM = 75% written in bold letters.

What is the meaning of TFM and what is its significance?

The chief ingredients of soap are fats – manufacturers either use animals fats or a vegetable oil, like coconut oil – and an alkali, usually caustic soda. The fats are the most important part of the soap.

TFM stands for Total Fatty Matter. This expresses the real soap content in the toilet soap. If TFM is given as 75% it means that the actual soap content is 75%, while the remaining portion consists of additives, which make it foam, or give it its colour, or keep it hard.

The higher the TFM percentage, the better is the quality of the soap. It is binding on the manufacturer to state how much fatty material there is in the soap.

 

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A car travelling in a straight line is approaching a corner. As the driver turns the steering wheel, the car begins to swing around the corner.

We know that an object in motion tends to travel in a straight line unless acted upon by a force.

The force that makes the car turn is the friction between the car tyres and the ground. If the friction is reduced by oil or water on the ground, then it may not be great enough to provide the centripetal force and then the car will not turn but carry straight on!

If there is a passenger in the car, he too will tend to carry straight on as the car turns the corner. But friction between him and the seat provides a centripetal force to make his direction of travel circular.

 

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Salk’s polio vaccine has two main drawbacks; it is not completely effective against one of the three strains of polio and it gives immunity only for a limited time which means the child has to be re-vaccinated regularly.

The oral polio vaccine was developed by Albert Sabin at the University of Cincinnati. It uses a small amount of live virus unlike the Salk vaccine which uses samples of the virus which has been killed by formation.

The Sabin vaccine is given orally. It gives immunity against all three strains of polio. It does not have to be taken as often as the Salk vaccine – just three separate doses with intervals of one month each between each dose and then a booster some years later.

 

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A road was being laid in front of our house and a man began pulling a heavy vibrating roller over the concrete that had been spread over the road.

Why are such vibrating rollers used in road building?

Whenever you pour rice into a tall container, you shake the container vigorously from time to time so that the grains settle down making room for more.

Similarly, when concrete is laid on roads, the road has to be shaken to enable the concrete to seep down into all the nooks and crannies and fill up all the crevices, leaving no air pockets.

The vibrating roller used by road-builders makes a lot of noise but all that it is doing is shaking up the road!

 

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Do sound waves die out or does a sound once made go on forever? What about light waves?

Sound waves behave like ripples in a pond after a stone has been thrown into it. The ripples get weaker and weaker due to friction of water and finally they lose their energy altogether and fade out.

Sound waves fade out for the same reason: they lose their energy due to friction of air.

Light waves are not affected by friction so they never die out. If we could travel fast enough to overtake light we would be able to see things that happened in the past, but of course travelling faster than light is impossible. Nothing in the Universe can travel as fast as light.

 

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My grandfather who had gone to an eye specialist said the doctor had examined his eyes with an ophthalmoscope.

What sort of an instrument is an ophthalmoscope?

An ophthalmoscope is an instrument used by eye doctors to inspect the interior of the eye. It directs a fine beam of light into the eye through the pupil, the black hole in the middle of the eye. The beam lights up the blood vessels of the retina at the back of the eyeball and the optic nerve. The ophthalmoscope has a magnifying glass which enables the doctor to study the area that is lighted up.

The eye is the only organ whose blood vessels and nerves can be looked at without cutting open the body.

The ophthalmoscope was invented by German scientist Hermann von Helmholtzin 1851.

 

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My friend says that there are some planes that you can fly by pedalling. Is that possible?

Man-made materials such as fibreglass make it possible to build very light aircraft whose propellers are turned by pedals. Some people have built such aircraft but the amount of physical effort needed to keep the propellers turning is too exhausting to keep up for long.

In April 1988, a Greek cycling champion named Kanellos Kanellopoulos pedalled a plane from the island of Crete to the island of Santorini – a distance of 120 kilometres. The plane weighed only 32 kilograms.

 

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I awoke from an action-packed dream to find myself safe and sound in bed.

Why didn’t my physical body react to what my mind was experiencing?

There are two types of sleep: regular sleep and dream sleep. During regular sleep your muscles remain ready for action. If you are uncomfortable, you move; if your name is called out you awaken.

Regular sleep gives way to dream sleep. When you’re in this state, breathing and heartbeat are irregular and the muscles that move your body become paralysed. It is this paralysis that prevents you from reacting to your dream and perhaps hurting yourself in the process. Sometimes, when you have a frightening dream, you realise that you’re dreaming and try to rouse yourself only to discover that you can’t move a muscle! You have to make an effort to rouse yourself.

Normally, dream sleep lasts for 10-15 minutes at a stretch. Then it gives way to regular sleep when you can move again.

 

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The printed message on the milk sachet said that the milk was pasteurised and homogenised.

I knew what pasteurisation meant. But what is homogenisation?

Milk contains fat in the form of very small globules. Being lighter than the rest of the milk, these globules float to the surface and form a layer of cream.

Homogenization prevents formation of this layer. This is done by forcing the milk through a narrow opening at great pressure thereby reducing the size of the globules to less than 2 microns. These microscopic globules cannot separate out from the rest of the milk and remain evenly distributed in it. Because of this, homogenised milk has a richer flavour and taste. It is also easier to digest than non-homogenized milk.

 

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Why do we become red in the face when we are embarrassed and why do we turn pale when we are frightened?

Sudden embarrassment stimulates the nerves called vasodilators and they cause the tiny blood vessels in the face and neck to expand. This allows more blood to flow through them giving the face a red appearance, and we say the person is blushing. When we are frightened, nerves called vasoconstrictors cause blood vessels in the face to constrict. The blood supply to the face is lessened and it takes on a pale appearance.

 

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My friend says semi-conductors are used in transistor radios. What is a semi-conductor?

Conductors are substances that allow heat or electricity to flow easily through them; insulators on the other hand, stop the flow of heat or electricity. In addition, there are some substances that stop the flow of electricity but become less resistant to it in some conditions and then allow electricity to pass. These are the semiconductors.

Semiconducting materials have made possible modern computers and many other important electronic devices like solar cells and transistor radios.

Two well-known semiconductors are germanium and silicon.

 

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