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Category Chemistry

Do you know how uranium for nuclear reactors is produced?

Uranium in its state is found in quantities that average about 4 grammes to every ton of rock. It is an extremely process to extract this mineral, from the rocks that contain it even when the deposits are relatively rich.

The best material for nuclear fission is Uranium 235, but natural uranium has only one atom of this structure for every has been extracted from rocks, the element has to be further processed to get the portion with the atomic structure needed for nuclear reactors.

Once the atomic reaction has been set in motion, the energy which is released mostly takes the form of heat. This heat led to a type of boiler where it generates steam that is later put to several uses. One kilogramme of uranium yields as much energy as 3 million kilogrammes of coal.

 

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Describe how a nuclear reaction takes place?

We speak of nuclear reaction whenever the nucleus of an atom undergoes any change in its properties any change in properties. For example, this could be the loss of one or more protons or other particles from within the nucleus, which in turn is possibly caused by the impact of other particles. In nature this process can take place spontaneously in certain substances and gives rise to radioactivity.

Radioactivity was discovered in 1896 by the French scientist Henri Becquerel who proved that pitchblende, a mineral that contains uranium, could darken photographic plates even if they were wrapped in dark paper. It became evident to Becquerel that a very penetrating from of radiation was involved.

We now know that this radiation consists of alpha particles and that radioactive materials also give out two other types of radiation: beta and gamma. Alpha particles are not very powerful and they can be stopped by a thickness of a few sheet of paper or by a few centimeters of air. Beta rays are more penetration but can be stopped by thick cardboard, a few meters of air or thin sheet metal. Gamma rays, like X-rays, are extremely penetrating and can be very dangerous to plant and animal life. To stop them several centimeters of metal thickness is needed to reduce gamma radiation to an acceptable level.

It was not simple to produce these rays artificially and it took many years of difficult research and complicated experiments. In the end the scientists succeeded. They bombarded the atoms of certain materials with particles taken from naturally radioactive material. By increasing or decreasing this bombardment, the scientists were able to break aparkthe protective shell of electrons and reach the nucleus of an atom.

In this way nuclear fission, or the splitting of the atom, was achieved. Under such bombardment to atomic nucleus splits into two smaller nuclei. As this happens, some neutrons are rejected by the splitting atomic nucleus and collide with the nuclei of neighbouring atoms. This sets off a chain reaction, releasing enormous quantities of energy which can go out of control with disastrous results.

Nuclear reactors are complicated structures in which the chain reaction from atomic fission can be set off continued and kept under control. In this way, an atom can be split without the risk of a terrible destructive explosion. Instead, the process is done gradually and a large amount of energy is produced.

Nuclear reactors are fuelled in different ways. Nuclear fuel must always be substances which cab set off a chain reaction when bombarded with neutrons. The most commonly used elements in fueling reactors are uranium, plutonium and thorium.

At the heart of the reactor there is the moderator which is a substance that slows down the speed of the neutrons and regulates their flow. The reactor is called fast if it uses fast neutrons and thermal if the neutrons have been slowed down, thereby transferring much of their energy to the moderator.

 

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What makes an atom?

Everything is made up of atoms which are the smallest parts of an element still possessing the chemical properties of that element. It is difficult to realize how small atoms are. They have a diameter of about one-hundred-millionth of a centimeter. At one time scientists believed atoms were little spheres that could not be broken, but we know that atoms are composed of other particles which are even smaller. Each atom is like a miniature solar system: at the centre it has a nucleus which consists of protons and neutrons around which electrons revolve.

The atom consists almost entirely of empty space and its entire size is that of the orbit of its outer electron, which revolves at extremely high velocity, forms an impenetrable shield. A propeller going round very fast will give us an idea of an electron. The electron seems to be at every point of its orbit at the same time because it goes round the nucleus so fast. That is why we say the atom consists mostly of empty space. The spherical shield formed by the revolving electrons prevents the emptiness between their orbits and the nucleus from being filled in normal circumstances.

The nucleus and the electrons each have a diameter of about one-tenth of a millionth part of millionth part of one centimeter. Nearly all the mass of the atom is contained within the nucleus. The electrons are very light compared with the protons and the neutrons which are 1,837 times heavier than the electrons.

Electrons have a negative charge and they are fixed to the atom and cannot break away from their orbits through centrifugal force because protons have an equivalent positive charge and the two balance each other. Neutrons have no electrical charge.

 

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What makes it snow?

Take a close look at some snowflakes. You can see that they aren’t drops, like rain; or lumps, like hail; or tiny beads, like sleet. They look more like little feathers.

Snow forms when water vapour in clouds freezes. It forms at the top of storm clouds where the air is colder. The frozen water drops grow as more water vapour freezes onto them. They turn into tiny, clear pieces of ice called snow crystals. A snowflake is actually a bunch of snow crystals.

When you look at a snowflake through a magnifying glass, you see a beautiful, lacy shape. Even when they may seem the same, no two snow crystals are exactly alike. Some are flat. Others are shaped like long needles. Most look like pieces of lace. Yet, in one way they are almost all the same. Almost all snow crystals have six sides.

Snow can form high in the sky even in summer. But when snow falls in summer, it melts and becomes rain as soon as it reaches warm air lower down.

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What is air made of?

Air doesn’t seem to be made of anything. It has no colour, taste, or smell, and you can see right through it. But air is made up of things. It is made of many kinds of gases. And these gases are made up of tiny bits called molecules.

Actually, everything on the earth is made up of molecules. Solid things, such as plants, animals, and rocks, are made of molecules. So are liquids, such as water, and gases, such as the ones in air.

In solids, the molecules are packed close together and hardly move. In liquids, the molecules are further apart and move faster. In gases, the molecules are very far apart and zip about rapidly. That’s why gases are so light that you can’t see them.

For us, the most important gas in the air is oxygen. We breathe to get oxygen into our bodies. Almost every kind of animal and plant in the world must have oxygen, or it will die.

Only about one-fifth of the air is made up of oxygen. Most of the air – nearly four-fifths – is nitrogen. The rest of the air is made up of many different gases. Water vapour and dust float in the air, but they are not part of the air.

If air is just floating gases, why doesn’t it float away into space? Because the earth’s gravity pulls at the air just as it pulls at you. The air can no more float off into space than you can!

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What is net-zero emission?

The U.S. president-elect Joe Biden has declared that the U.S. will return to the Paris Agreement and vowed to reach net-zero emission by 2050. China has committed to achieving net-zero carbon emissions by 2060. South Korea, New Zealand, Australia, Brazil, Iceland and scores of other countries and corporates such as Pepsico have all set net-zero goals. A new study shows that climate disaster could be curtailed within a couple of decades if net-zero emissions are reached.

So, what does net-zero mean?

Do not be confused with the word ‘zero’. Net-zero emission does not necessarily mean reaching zero emission. Under a net-zero scenario, emissions will still be generated, but this emission must be removed from the atmosphere through measures such as reforestation and artificial carbon sequestering. In other words, net-zero means achieving a balance between the greenhouse gases put out into the atmosphere and those removed. The term “carbon-neutral” is sometimes used instead of net-zero, and they broadly mean the same thing. It’s not just countries that can achieve net-zero emissions, even a state, city, company or a single building can also strive to achieve net-zero emissions.

However, climate activists such as Greta Thunberg are demanding for zero emissions, meaning no emissions are produced in the first place.

How can net-zero be achieved?

  • By reducing the use of fossil fuels and by adopting renewable energy sources.
  • By developing energy-efficient technologies. 
  • By adopting massive reforestation or tree-planting measures.
  • By investing in technologies such as carbon sequestration that can remove carbon from the atmosphere. Carbon sequestration is the process of capturing and storing atmospheric carbon dioxide underground permanently and safely.

However, no technology or quantity of trees planted could offset the emissions currently generated globally, unless every country and every household is part of this solution.

 

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What do chemists do?

Chemists. One of the physical sciences is chemistry. Chemists study chemicals and other materials to find out what they are made of. They also learn how these things change when they join with other substances. Chemists take molecules apart and put them together in new ways. They try to find out how chemicals can be used to make things people need, such as fuels, medicines, plastics, and thousands of other materials. Some chemists study how light, heat, and other forms of energy change chemical substances.

A chemist will often work as part of a larger research team in order to create much needed compounds for use in a wide variety of practical applications. A chemist also works to improve the quality of established chemical products and utilizes advanced computer programs to establish new technologies in the field.

Almost every industry benefits from the theories and chemical compounds brought about by research in the chemical sciences.

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What exactly is nuclear energy?

All things – even you – are made up of billions and billions of “bits” that are smaller than anything you can imagine. These “bits” are called atoms. Atoms are the tiniest parts that something can be broken into and still be the same stuff. For example, one atom of gold is the tiniest bit of gold possible.

Special machines can split certain kinds of atoms into even smaller parts. When atoms split, they give off energy. The part of the atom that splits is called the nucleus, so the energy is called nuclear energy.

The energy given off by atoms when they are split is in the form of heat. So a machine that splits atoms can be used the same way a fuel-burning engine is used. The machine makes heat. The heat can be used to run generators that make electricity and to run other machines, too.

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What is Chemical Energy?

You have seen candles burning. An orange flame dances around the wick, while the wax melts underneath and drips down. The candle gets shorter as the wax melts.

The candle wax has a kind of stored-up energy. It is a fuel. A fuel is something that is burned to make light, heat, or a push that makes things move. The coal, oil, and gas used to heat homes and other buildings and to cook food are fuels. The petrol in a car and the wood in a fireplace are fuels, too.

The same thing happens to every kind of fuel when it burns. When it starts burning, the heat makes it break down and change to other things, such as ashes. As the fuel breaks down, it gives off energy. Some of the energy is light, and some is heat.

When petrol is burned in a car engine, the heat energy makes the engine push. The push from the engine makes the car run.

The energy stored in a fuel is called chemical energy.

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What do we know about the platinum group of metals?

A group of six metals – ruthenium, rhodium, palladium, osmium, iridium, and platinum-are known as the platinum group of metals or PGM. The group is called by this name because platinum is found more than the others though all of them are very rare.

The platinum groups of metals have physical, chemical and anatomical similarities. They are dense, stable and are often recycled to have longer lives. The group has a variety of highly specialized uses.

Platinum is a silvery white metal that is more expensive than gold. It is used to make jewellery. Platinum and palladium are often used as catalysts. Iridium and rhodium are harder and have a lot of alloying applications. There are very few minerals containing the platinum group of metals, and they are found mainly in South Africa and Russia.

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