The problem with plastic


 



 



 



Plastic is a very useful material but it also causes problems. Plastic does not rot away. So if plastic bottles or bags are dropped as litter they stay there for a very long time. Plastic litter spoils our environment.



 



 



 





 



 



A lot of plastic is thrown away.



Every year we throw away millions of tonnes of plastic. Most of it ends up in landfill sites and is buried under the ground. Most plastics do not rot or break down so they will be there for a very long time.



 



 


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Plastics for health


 



Plastic can be used to keep us healthy. Hospitals use plastic because it is clean and safe. Plastic tubes are used in hospital to give us medicine. Blood is stored in plastic bags. We are given injections with plastic syringes.



 



 



 





 



 



These teeth are made from plastic.



As people grow older, they may lose their teeth. If this happens, they can have new ones made from plastic. Plastic teeth are hard perfect for chewing. They are shaped to look exactly like our own teeth. Even better, they will never need fillings!



 





 



 



This plastic hand looks real.



Plastic is used to make artificial parts of the body such as legs, arms, hands and ears. They are made to look real and are used to replace those lost in accidents or through illness. Artificial legs help people to walk.



 



 



 



 



 





 



 



 



 



Plastic can help us move again.



When we get older, our joints such as the hip or knee sometimes wear away and become very painful. An artificial joint made from plastic and metal can be used to replace the damaged joint so that people can move again without pain.



 



 



 


Plastic clothes



 



 



Some of our clothes are made from plastic. Fabrics made from plastic are easy to look after. They do not get dirty very easily or need much ironing. Plastic fabrics last a long time and do not lose their shape and become baggy.



 



 



 



 





 



 



 



These threads are made from plastic.



Plastic fabrics are made by forcing hot, runny plastic through very fine holes in a machine. The plastic comes out in thin fibres which are used to weave into fabric. Fibres made from plastic are called synthetic fibres. Sometimes synthetic fibres are mixed with natural ones such as cotton.



 



 





 



 



These clothes are made from plastic.



A special type of plastic material is designed to be fireproof. This material is worn by firefighters and racing car drivers. Before it is used, the material is rested with a white-hot gas flame to make sure that it will protect whoever wears it.



 



 



 



 





 



Tents made from plastic cloth keep out the rain.



Fabric can be made waterproof by adding plastic. Some fabrics are just coated with plastic on one side. Other fabrics are put in a bath of plastic paste so that the paste soaks into the fabric.


Which things wrapped in plastic?



 



All wrapped up                                                 



Many of the things we buy are wrapped in plastic. The wrapping helps to keep things fresh. It can also tell us about the food we are buying. The words printed on a plastic yoghurt pot tell us what flavour yoghurt is inside.



 



 



 



 





 



 



If this bottle of water is dropped it will not break.



Plastic is a good material for packaging because it doesn’t break easily like glass. Plastic is very light compared with glass or metal. This means it is easier to transport plastic bottles to shops. Vans and Lorries need to use less fuel to transport plastic bottles.



 



 





 



 



Plastic bottles keep chemicals safe.



Plastic is waterproof and can be resistant to chemicals. Plastic can be used to package harmful chemicals. Even if the plastic bottle is dropped the chemical won’t spill because plastic is shatterproof.



 



 



 



 



 





 



 



 



 



The plastic wrapper keeps the food fresh. 



Plastic packaging is safe and hygienic. It helps to keep food fresh for longer so that less food is wasted. It protects the food from being damaged. The plastic film we use to cover foods is strong, waterproof, airtight and germproof.


Bubbly Plastic


 



Plastic can be made into foam. Foam is made by blowing bubbles of gas into melted plastic. Some foams have very tiny bubbles inside and others have bubbles that are big enough to see. Plastic foams are used in many different ways.



 



 



 





Plastic foam helps to keep things warm.



Plastic foam is a good heat insulator. This means it does not let heat pass through it. We use plastic to insulate our homes and stop heat being lost through the walls and roof. Buildings can be insulated by putting sheets of foam behind walls, floors or ceilings. We also use plastic foam to keep food and drinks warm.



 



 



 





 



 



Foam plastic is used to make furniture.



The soft furniture that we use in our homes is filled with spongy plastic foam. The air bubbles in the foam make it soft to sit on. Some foam gives off dangerous fumes if it catches fire. New furniture is made with foam that doesn’t easily burn.



 



 





 



 



Plastic foam helps to keep things safe from knocks.



Polystyrene plastic is used to package fragile objects that may easily get broken. The small pieces of polystyrene fit around an object and protect it against knocks. Polystyrene is strong but lightweight. It is used to make cycle helmets to protect our heads.


Making things with plastic


 



 



There are different ways of making plastic into the shapes we need. Many plastic objects are made using moulds so they are all exactly the same. This means that plastic objects, such as Lego building bricks, will fit together.



 



 



 





 



 



 



These bottles were shaped by a mould.



Plastic bottles are made by a method called blow moulding. A tube with a blob of runny plastic on the end is put inside a mould. Air is blown down the tube. The plastic inside the mould blows up like a balloon. It presses against the mould to make a hollow bottle shape.



 



 



 





 



 



 



Hand-shaped moulds are dipped in plastic.



Plastic gloves are made by dip-moulding. A solid hand-shaped mould is dipped into hot liquid plastic. It comes out covered in a thin layer of plastic. When the plastic is set and dry the finished glove is peeled off the mould.



 



 



 





 



 



 



Plastic is squeezed through a hole to make a drinking straw.



Drinking straws are made by a method called extrusion. Hot, runny plastic is forced through a hole. As the plastic pushes out through the hole, it forms into a tube shape, just like icing piped onto a cake.


What are the different types of plastics?



 



 



 



 



There are hundreds of different kinds of plastic. Some plastics are hard and others are soft and bendy. Plastic can be thin, thick, coloured or see-through. Plastic is a very useful material and we use it in many different ways.



 



 



 



 



 



 



 





 



These things are made from different types of plastic.



There are two different groups of plastic. The plastics in one group melt when they are heated, and become solid again when they cool. These groups of plastics are used to make bottles and clothing. The other groups of plastics do not change shape when they are heated. They are used to make objects such as saucepan handles and CDs.



 



 



 


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How is plastic made?


 



 



 



 



 



Oil is drilled and pumped out of rocks in the ground. Sometimes oil is found in rocks under the sea. A platform called an oil rig is used to reach under-sea oil. It stands or floats in the sea and drills the oil from the rocks.



 



 



 



 





 



 



Oil is taken here to be made into different things.



Crude oil is taken to an oil refinery by a pipeline or huge oil tanker (ship). The refinery is like a huge factory where the oil will be separated into different things. Care must be taken when transporting oil. If the oil spills it can damage the natural environment.



 



 



 





 



 



 



 



The oil is heated and separated in a big tower. The oil is separated into different chemicals by heating it in a huge tower. As the oil gets hotter the different chemicals in it boil, turn into gases and separate out. When the separate gases cool down again, they turn back into liquids. The liquids are collected. Naptha is one of these liquids. Naptha is turned into plastic called polythene, which is used to make many different plastics.


What is the history of plastic?

               Around 150 years ago, people did not have plastic things. Now plastic has become an important part of our everyday lives. Hundreds of different types of plastic have been invented. Think about how many plastic things you use each day.



 





 



 



Cotton plants were used to make the first plastic.



The first plastic was made in 1862 from cellulose, which is a material found in plants. Alexander Parkes used cotton to make plastic called celluloid that could be moulded into many different shapes. This first plastic was used to make ornaments, cuffs and collars.



 



 



 





 



The telephone here is made from coal tar.



In 1907, a new plastic called Bakelite was made from coal tar. This plastic could be moulded into any shape and it would not burn, boil or melt once it had set hard. It was used to make telephones and radios.



 



 



 



 





 



 



This surfboard is made from a new strong type of plastic.



New plastics have been invented that are strong, durable, light and flexible. They are used to make sports equipment such as windsurf boards, ropes and bullet-proof vests.


What is Plastic?


 



 



 



                Plastic is a man-made material. It is an amazing material that is used to make many different things. Every day, all over the world, people use or wear things made from plastic.



 



 



 



 



 





 



               Most plastic is made from oil. Crude oil is the raw material that most plastics are made from. Oil is a fossil fuel. It is made from the remains of tiny aquatic plants and animals that lived millions of years ago. Today, oil is found in rocks that are deep under the ground or under the sea.



 



 



 



 


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What are Antifreeze Compounds?


               Antifreeze compounds are those substances which, when mixed with some other liquid, lowers its freezing point. In cold countries, the liquids used in the cooling systems of cars and buses get frozen in winter months. Antifreeze compounds are used to prevent this freezing. In other instances, snow gets deposited on the wings of aircrafts flying in the cold areas. To prevent this, antifreeze compounds are used. In cold storages, special materials are used as antifreeze compounds.



               The main ingredient of an antifreeze compound is usually a type of alcohol. Ethylene glycol is the basis of the most common antifreeze compound. This compound mixed with water is used in the radiators of automobile engines to lower the freezing point. It helps the internal combustion system of an engine to function normally without being frozen in cold. In winter season, this is also used with or without water in order to prevent the freezing of the cooling system. Sometimes, methyl alcohol is also used as an antifreeze compound in internal combustion engines. Methyl alcohol lowers the freezing point of water. When the risk of freezing is over, these antifreeze substances are often drained out of the cooling system because, due to evaporation, an antifreezer often loses its power, and can no longer protect the cooling system from rust and corrosion. It can also go into the block of an engine and cause problems in lubrication.



               Ethylene glycol is used as an antifreezer to prevent snow from collecting on propellers and wings of air planes. Glycerol and ethyl alcohol are used to protect drugs and cosmetics from freezing during storage. Calcium chloride and sodium chloride are used in refrigeration equipments. Besides these, there are many other substances which are used as antifreeze compounds.


What are fuel gases?


               The use of gas for cooking and heating began in the middle of the 19th century with the introduction of gas stoves in 1840 and gas fires in 1855. The most important gaseous fuels are natural gas, coal gas and water gas. Nowadays, a certain amount of gas is made from oil. Today other processes have also been developed for the manufacture of a substitute or synthetic natural gas from coal.



               Natural gas is obtained from the deposits of oil. This gas was once considered a hindrance during drilling of oil and was merely disposed off by burning at the oil fields. But now it is used as a fuel and feedstock. Natural gas and oil were formed from plants and animal remains at different depths inside the earth over million years of time. These are fossil fuels and were changed into gas or liquid at different temperatures by constant chemical processes beneath the earth. Natural gas is mainly composed of 85% methane, 10% ethane and the rest being propane, butane and nitrogen. It produces sufficient amount of heat on burning.



               Coal gas is a mixture of gases that are given off when coal is converted into coke. The average composition of coal gas by volume is hydrogen 50%, methane 30% carbon monoxide 8%, oxygen, carbondioxide and nitrogen 8% and other hydrocarbon about 4%. This gas is produced by heating coal in the absence of air. Coal is heated in retorts or ovens to a temperature of approximately 1350°C so that it softens and releases its gas. This gas is thick and brown in colour because of the presence of coal-tar vapour and is used as an important fuel in homes and factories. Nowadays, however, it is being largely replaced by natural gas.



               Water gas is a mixture of hydrogen and carbon monoxide. It is made by passing steam over red-hot coke. It is used in industries. It is bluish in colour. When water gas is mixed with coal gas, the mixture is known as town gas.



               Oil gas is made by cracking the crude oil. Unlike other inflammable gases it does not contain many impurities and is thus of high quality. It contains mainly methane, acetylene and benzene. It is mixed with town gas and distributed in the normal way through a system of pipelines in advanced countries. This gas produces very small amounts of smoke and ash.



 


What is Carbon Cycle?


               Of all the elements known to man, carbon is one of the most important for him. Diamond, the most valuable gem, is a form of carbon. Graphite is also a form of carbon which forms the lead of lead pencils. Again, coal which is a main source of heat and power in the present age is mostly carbon. The most important fact about carbon is that it is a necessary element for all living things. In fact, scientists believe that wherever carbon has been found in any quantity on the earth, life in all probability existed there. Carbon is the most widely distributed non-metallic element and it is a common constituent of all organic compounds. Do you know what Carbon Cycle is?



               Carbon cycle is the process of constant circulation of carbon between living organisms and the atmosphere. It maintains a balanced percentage of carbondioxide in the air. The main source of carbon for all lives is the carbondioxide gas in the atmosphere. This gas is taken from air and returned to it by all organisms. In this continuous cycle, the limited carbondioxide in the air is being constantly re-used.



               Green plants take in carbondioxide gas from the atmosphere; combine it with water from the soil, to make more complex carbon compounds. Carbondioxide is returned to the air by plants in two ways. Firstly during night they give off carbondioxide. And secondly, when they die and their remains decay, carbondioxide is released into the air.



               Animals, including human beings, get some carbon from the carbondioxide in the air. However, most of their carbon is obtained from plants, vegetables, fruits or cereals. All animals return carbon to the air by breathing out carbondioxide during respiration. Like plants they also give out carbondioxide when they decay after death. Carbondioxide is also released when animals or plants are burnt. Again, when fossil fuels like coal, petroleum or natural gas are burnt, carbondioxide is released into the atmosphere.



               Today, Carbon Cycle is in danger by the increased consumption and burning of fossil fuels and large tracts of tropical forests. As a result, carbondioxide is building-up in the atmosphere breaking the equilibrium and contributing to the global warming as termed by the scientists.



 


What is Ceramics?


               The word ‘ceramics’ has its origin in the Greek word Keramos, which means “potter’s clay”. Today the word refers to all types of pottery, whatever its composition or use. All ceramics are made from various clays, together with materials such as flint, felspar or china clay.



               However, strictly speaking ceramics are compounds of silicon, carbon, oxygen and nitrogen combined with other elements like sodium, potassium, calcium, barium etc. The principal raw material used in the manufacture of ceramics is clay. These clays are formed by decomposing natural rocks which are exposed to the wearing action of air and water. Granite is the rock which provides the bulk of useful clays. It is composed of quartz, mica, felspar etc. These clays are crushed and ground into fine particles. The particles are mixed and moisted with right proportion of water, which makes the particles flexible for shaping. Different methods are used for getting the desired shape.



               After the product has dried, it is heated. This process takes place in a special type of furnace called kiln. Ceramics are heated at temperatures ranging from 650°C to 1650°C. Firing makes the products hard in the desired shape and turns their glaze into a smooth coat. This process also makes the product leak-proof, durable and decorative.



               Clay and shale are used to make building products, such as bricks and drain pipes. Calcium silicates are used in making the cement. Gypsum is used in the manufacture of plaster. Porcelain is used in making bath-tubs, sinks and toilets. Bowls, cups and plates are also made from porcelain. Artificial bone joints and false teeth are made from porcelain.



               Some ceramics such as alumina and porcelain, do not conduct electricity and used as insulators in automobile spark plugs, electric power lines. Some types of capacitors are made from Barium titanate which is a ceramic material. Refractories are another important group of ceramic products used for lining furnaces. They resist heat and chemical action. Alumina, silica and magnesium compounds are used as refractories. Uranium oxide ceramics are used as fuel elements for nuclear reactors. Alumina in the form of ruby is used in the making of lasers, which produce extremely strong light beams.



 


What is the absolute zero?


               It is our common practice to measure our body temperature with the help of a thermometer when we feel feverish. In ordinary thermometers, the lowest temperature is marked as 0°C. Today scientists can produce temperatures well below 0°C. Kelvin William Thomson a British Physicist first pioneered the absolute scale of temperature. The scale which is used to measure low temperatures therefore called ‘Kelvin’ scale or absolute scale of temperature.



               Theoretically the lowest possible temperature which a gas can attain is known as absolute zero. In centigrade scale it is equal to -273.15°C. This is based on the theory that the volume of a gas reduces in correspondence to the fall in temperature. So according to this theory, the gaseous volume would disappear and would loose all its kinetic energy if its temperature was lowered to -273.15°C or absolute zero. The gas molecules would be completely at rest, and it would not possess any heat. In practice, however, all gases change to liquids and then to solids before their temperature reach absolute zero.



               Scientists have never been able to reach absolute zero in their laboratory experiments. The lowest recorded temperature so far was achieved by magnetizing copper nuclei at a low temperature. When the electromagnet was switched off, the copper nuclei became demagnetized; the temperature fall was upto a million part of a degree above absolute zero.



               Materials react strangely when cooled to a temperature near absolute zero. At this temperature, oxygen gas freezes to a bluish white solid, and a rubber ball becomes so brittle that it shatters instead of bouncing. Mercury, normally a liquid, becomes and shines like hard silver. Hydrogen becomes a liquid and begins creeping into the sides of its container. Natural gas is shipped around the world in special containers after being cooled and liquefied at a low temperature.



               The Kelvin scale is used for scientific measurements, e.g. the liquefaction temperature on the Kelvin scale for Hydrogen is 20K and for liquid Helium it is 4.2K.