Category Science

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.

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.

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.

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.

Continue reading “What are the different types of plastics?”

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.

               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.