Category Chemistry

How is steel made?

            Steel is made from iron, which is usually mined in the form of iron ore. The ore needs to be smelted in order to extract the iron. Smelting is done in a blast furnace, where coke and limestone are added to the iron ore. This mixture is heated to a very high temperature and air is blown through it. The molten iron is drawn off.

            To make steel, iron is mixed with carbon and other metals to give it extra harness. There is about 1.6 percent carbon in most steel. Other forms of steel contain elements such as chromium and nickel to prevent rusting. Ordinary carbon steel rusts as easily as iron, and must be protected with paint or other coatings.

Picture credit: google

How do nuclear power stations work?

 

               Once nuclear fission takes place inside a nuclear reactor, the chain reaction has to be controlled, or moderated. The reactor’s core of uranium is surrounded with a substance that slows down and absorbs the escaping neutrons. The moderating material becomes heated. In a nuclear power station, steam generated by this heat is used to drive the turbines to produce electricity.

Picture credit: google

How is nuclear energy produced?

               Nuclear energy is produced by changes in the nucleus of the atom of a radioactive element such as uranium or plutonium. This process is called nuclear fission. The nucleus is split by bombarding the atom with a neutron particle. Each time the uranium atom is split in this way, it releases energy. It also produces three more neutrons, which then go on to split other uranium atoms. This is called a chain reaction because, once started, it will continue the process of nuclear fission while releasing very large amounts of energy.

Picture credit: google

Natural Properties

 

What are acids?

               Acids are a group of chemicals with very similar properties. They all have a very sour taste and are capable of burning the skin, although some are much more powerful than others. Many metals will dissolve when they come into contact with acids. This is because acids can release hydrogen ions when they are dissolved in water. Strong acids such as hydrochloric, sulphuric and nitric acids release many hydrogen ions, so they react very fiercely with many substances. Acetic acid, which is an ingredient of vinegar, releases only a limited number of ions and is not a strong acid. This is the reason why it can be used safely in our food.

 

 

 

How can we identify acids and alkalis?

               Dyes called indicators show very quickly if a substance dissolved in water is acid or alkaline. One of these dyes is litmus. If a piece of paper impregnated with litmus is dipped into a solution, it immediately turns red if the solution is acid. If the solution is alkaline, the litmus turns blue.

               A similar dye is present in vegetables such as red cabbage and beetroot, and this dye changes colour in the same way during cooking. If your tap water is hard (alkaline, because it contains dissolved lime), the vegetables will be coloured a deep purplish-blue. Red cabbage and beetroot are often pickled in vinegar, as the acid in vinegar gives them an attractive deep-red colouration.

Pictures credit: google

Natural Properties

 

Why does my breath ‘steam’ in cold weather?

               When water boils the steam it produces is not visible while the water remains at boiling point. As the steam cools it forms tiny droplets of water, making it look cloudy. This is called water vapour, which is what you see when your breath ‘steams’ in very cold weather. Explorers in the Arctic and Antarctic find that water vapour condenses and freezes to form ice around their nostrils and mouth.

 

 

 

What happens when iron rusts?

               The reddish powdery rust that forms on unprotected iron and steel is the result of a process called oxidation. It takes place when the metal reacts with oxygen from the air and water. Both air and water are needed for rusting to take place. This form of rusting eats into the metal until it collapses into scales and dust of iron oxide.

               When aluminium is cut it oxidizes very quickly, but the newly formed layer of aluminium oxide prevents exposure of the metal to more oxygen. The aluminium oxide stops the process of oxidation, so the metal remains bright and shiny.

Pictures credit: google

Natural Properties

What happens when a liquid boils?

               When a liquid is heated, at a certain point it begins to change to a gas, or vapour. This happens because at high temperatures the molecules in the liquid move faster, until they escape into the air. Light molecules escape more easily than heavy a molecule, which means that heavy, thick liquids only boil at very high temperatures.

               The boiling point of a liquid depends on the air pressure. The pressure becomes lower at altitude, so high up on a mountain slope; water boils at a much lower temperature than normal. Water boils at 100°C at sea level, but at only 72°C at an altitude of 3,048 m.

 

What is evaporation?

               Evaporation happens when a liquid or a solid changes to a gas. It is a similar process to boiling, because it involves the molecules of a liquid passing into the air. The process of evaporation is much slower when the air above the liquid is already full of molecules of vapour. For example, water will evaporate only very slowly on a warm, damp day when the air is already saturated with water vapour.

               As a liquid evaporates it loses heat energy, making it cooler. This is the principle on which refrigerators and air conditioners work. Evaporation of water from the seas and land produces water vapour in the form of clouds, which eventually drop water back onto the Earth’s surface as rain.

Picture credit: google