My Science School

Let us now talk about something that was common in ancient India. Very often, mysterious red lights would flare up in temples to the awe and terror of worshippers, who believed it to be a divine light.

Actually, it was the handiwork of priests who would quietly set fire to small balls of a mixture that contained strontium salts. Strontium catches flame spontaneously in air and strontium salts impart a beautiful crimson colour to flames. For this reason, strontium is used in fireworks as well.

Strontium is a soft silvery metal that is found chiefly as celestite and strontianite. It was in 1808 that Sir Humphry Davy isolated strontium. But much before that, our ancestors knew about this metal and had used it in quite a cunning manner.

You might have heard stories about ships that sent red flares as a symbol of trouble. Just like the ones used in ancient Indian temples, these ships too used strontium salts. It would not be wrong to say that strontium has saved many lives.

Let us now take a look at how glass is made. Glass is made by melting a special type of sand called silica sand. The sand melts at 1700 degree Celsius; it must be melted and cooled down quickly. This process requires a huge amount of energy and will produce a lot of heat.

To make things easier, sodium carbonate is added. Sodium carbonate breaks down in the heat to form sodium oxide, and reduces the melting temperature. This does not completely solve the problem.

The glass made after adding sodium carbonate would dissolve in water. This is where calcium carbonate comes into the scene. When calcium carbonate is added to glass, it forms calcium oxide in the glass. About 90 per cent of glass in the world is made in this fashion.

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You cannot lead an active life without calcium. Be it walking, running, playing games, lifting things or even sitting straight, you cannot do any of these if not for calcium.

Every cell in our body needs calcium. Calcium helps our muscles work and send nerve impulses. It helps your body to heal cuts, scrapes and other injuries. Our bones store calcium that is necessary for our blood and cells; our bones are built and strengthened with calcium right from the day we are born.

If our diet does not include enough calcium, our body will consume the calcium that is stored in the bones. This will eventually make our bones weaker. So, it is important to have calcium rich foods like curd and milk.

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Chalk is a white crumbly rock made of microscopic shells and is rich in calcium carbonate. Chalk is softer than limestone and is used to make a substance called putty. Putty is used to fill holes in woodwork, give a smooth finishing to the walls of buildings and seal glass into windows. Chalk is also ground into a powder called whiting, which is used in crayons, rubber paints and cosmetics.

Limestone often contains the fossils of dead animals and plants that were trapped in between the layers of sediment. Limestone is hard enough to be qualified as a building material; it is used to construct buildings, walls and paving stones. Sometimes, limestone contains phosphates. This is used to make fertilizers.

Marble is formed when chalk or limestone is buried deep underground. The pressure and heat changes the limestone or chalk into marble. It is hard, yet shiny and beautiful. Therefore, marble is used in flooring. Many sculptures and buildings around the world are made of marble. The famous Taj Mahal is built entirely of marble.

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Calcium makes about 3.6 per cent of the Earth’s crust. But it is rarely found as a free metal. Calcium is abundant on the surface of the Earth and is mostly found as chalk, limestone, or marble.

Let us now look at how these calcium deposits are formed. The shells of living things in the ocean are made of calcium carbonate. When they die, they sink to the bottom of the ocean. Over the years, these form layers of sediments. As the layers build up, their weight squeezes the water trapped between and they stick together. Over thousands of years, the shells are transformed into sedimentary rocks called chalk, limestone and marble.

It was Sir Humphry Davy who isolated calcium for the first time in 1808.

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To maintain good health, the human body needs a lot of minerals like iron, calcium and sodium. We have already discussed how our blood is enriched by iron. But, very few people are aware of the enormous role magnesium plays in our bodies.

After oxygen, water and food, magnesium may be the most important element needed by our bodies. In fact, it is by far the most important mineral in the body.

Magnesium is necessary for over 300 different biochemical reactions that help the functioning of the human body. Magnesium is necessary for the growth and strength of bones and teeth. It plays an important role in the synthesis of protein and is responsible for fighting infections. Magnesium is vital for muscle contraction and the functioning of nerves.

Needless to say, we need to eat a lot of food that is rich in magnesium like nuts, whole grains, dark green vegetables, seafood, and cocoa.

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Iron and steel corrode after being exposed to oxygen or water. Corrosion is a huge trouble for ships, pipelines and oil rigs.

To prevent the troubles caused by rusting and protect the iron, another metal is used. Magnesium and zinc are often used for this purpose.

Magnesium is either attached with a cable or bolted to an object made of iron or steel. This method is known as sacrificial protection. As long as magnesium stays in contact with the steel or iron, the rust will form on the magnesium bar, since it reacts more strongly with oxygen and water than either of the other two metals. When the rust attacks the magnesium bar, it will be eaten away.

One magnesium bar must be replaced with another to protect iron or steel. Since magnesium is willingly allowed to be destroyed for the protection of iron or steel, this method is known as sacrificial protection.

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Magnesium was not discovered until the 19th century. But much before that, humans had been using compounds of magnesium. Isolating magnesium is a tough task. This is because the compounds of magnesium are highly stable and cannot be broken down easily.

Careful studies of magnesium and its compounds began in the mid 1700’s. Some of the earliest studies on magnesium and its compounds were carried out by Joseph Black, a Scottish physician and chemist.

He conducted various experiments on compounds of magnesium and published his studies in an article. Black’s article became famous in the scientific circles and he is sometimes given credit for ‘discovering’ magnesium.

Though Black’s experiments were famous, it was Sir Humphry Davy who first isolated magnesium. Davy passed an electric current through melted magnesium oxide. The current caused the compound to break apart, forming the impure magnesium metal and oxygen gas. But this was a strenuous task, requiring a large battery with 200 pairs of metal discs to isolate the metal!

In 1798, a French chemist, Louis-Nicolas Vauquelin discovered a brittle, steel-gray metal. It was found as a component of coal, oil, certain rock minerals, volcanic dust, and soil. This metal was named beryllium.

Beryllium is used to make an alloy - beryllium copper- which has a wide variety of uses. Beryllium copper is used to make springs, electrical contacts, spot-welding electrodes, and non-sparking tools.

This alloy absorbs a lot of heat energy without becoming as hot as other metals. It is used in high-speed aircraft, missiles, spacecraft, and communication satellites for the same reason. It is also used to make windshield frames, brake discs, support beams, and other structural components of the space shuttle.

Though ordinary light cannot pass through beryllium, X-rays seep through it. So, it is used in the windows of X-Ray machines and radiation detectors. It is used to make computer parts and instruments where lightness, stiffness, and stability are required and even in nuclear reactors.

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The method of spectroscopy was instrumental in the discovery of some elements. Spectroscopy is the process of analyzing light produced when an element is heated. Each element produces a different light when heated.

The spectrum of an element consists of a series of coloured lines. In many cases, the amount of an element present in a sample is too small. But, the element is much easier to detect by spectroscopy.

Caesium was discovered using spectroscopy by two German scientists, Robert Bunsen and Gustav Kirchhoff. It happened in 1859. Bunsen and Kirchhoff discovered caesium while they were busy studying a sample of mineral water taken from a spring.

At first, they identified the spectral lines for sodium, potassium, lithium, calcium, and strontium; these elements were well-known at that time. After removing these elements from the sample, they could still see two blue lines in the spectrum.

This was due to the presence of caesium. It was Bunsen who suggested calling the element caesium; it is derived from the Latin word for ‘sky blue’.

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Francium is one of the most radioactive elements in nature. Apart from being one of the least stable elements, it is also the second rarest naturally occurring element on Earth.

Marguerite Perey discovered francium in 1939. She chose to name the metal after France, the nation of its discovery. Francium is formed when uranium and thorium ores decay. It is usually made from radium in nuclear reactors.

Numerous experiments and calculations have been carried out since francium was discovered to study its basic physical and chemical properties. The half-life of this element is around 22 minutes.

Due to its high reactivity, francium is not used commercially. However, from experiments conducted on rats, scientists have proved that francium is a promising aid in the early diagnosis of cancer. This is because francium accumulates in cancerous tissues.

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Like sodium, potassium is another metal famous for its reactivity; it is so active that it never occurs freely in nature, but only as compounds. This was why our ancestors did not know about the existence of this metal. Potassium was not known to the world until the 19th century.

The term potassium comes from potash. Early humans were familiar with potash, a compound of potassium that was formed when wood burns. Wood ash was washed with water to dissolve the potash. It was then recovered by evaporating the water. By the late I700’s, chemists were reasonably sure that potash contained elements they had never seen. They tried to think of ways to break potash down into its elements. However, it was the English chemist Sir Humphry Davy who finally found a way to make potassium from potash.

In 1807, Humphry Davy prepared potassium in its pure form for the first time in the world. He was using his newly invented method of isolating elements, known as electrolysis. In electrolysis, electric current is passed through a molten or melted compound which breaks the compound into its elements.

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The reactivity of rubidium might surprise you. In fact, rubidium is one of the most reactive of all the metals in the world. It catches fire when exposed to oxygen in the air, and burns up with a bright pinkish purple flame to become a yellow powder called rubidium superoxide.

If you try to put out the fire with water, it will only make matters worse. Want to know why? Rubidium reacts vigorously with water as well! When exposed to water, it produces hydrogen gas, which catches fire and burns.

By now, you would have understood why it is difficult to store rubidium. Most of the containers are not suitable for preserving or storing rubidium. If you place it in an ordinary glass container, the rubidium will destroy the glass at high temperatures. The only solution is to store it in special glass tubes in which a vacuum is maintained, or in flasks of kerosene or paraffin oil.

The name ‘rubidium’ comes from the term ‘rubidus’, which was a word once used to refer to the deepest red.

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Sodium is notorious for its reactivity; it reacts quickly with air and water. Therefore, sodium is rarely used by itself though it is an important industrial metal. Let us now take a look at some of the uses of sodium.

Sodium is used for manufacturing many organic compounds and also to improve the structure of certain alloys. It is an indispensable element in the manufacture of soap, paper, textiles, glass and petroleum. We all consume sodium on a daily basis. There is a great variety in the compounds of sodium. Sodium silicates are used as fillers for salt, and in detergents. Sodium tetra borate is known as borax. Sodium hydroxide is used in the manufacture of paper, soap, rubber and rayon. It is also used for refining oil. Sodium fluoride is used in antibiotics, rat poison, and in ceramics. Sodium hydroxide gets grease out of the drains; it is also used to make liquid soap.

We consume sodium on a daily basis. The table salt that we use in our food is sodium chloride, a compound of sodium. Baking soda that we use to make baked goods is actually sodium bicarbonate, another compound of sodium.

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You might have heard of lithium batteries that are used in laptops and mobile phones. Lithium batteries replaced the lead-cadmium batteries as they are lightweight and not as toxic as their counterparts. The devices that use lithium batteries range from watches to spacecraft.

Lithium-6 is an isotope of lithium which is used as a fuel for nuclear reactors. Lithium is preferred as a nuclear fuel, because it is cheaper and more available. In addition to being a nuclear fuel, it is also used in rockets and spaceships. If lithium is added to water it produces highly flammable hydrogen.

Ceramics, enamels, glass, lubricants, rubber products and certain dyes also use lithium. It is used in some medicines as well. Lithium is used as an air purifier in submarines, aircraft and even air conditioners.

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