My Science School

 

 

 

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.

 

 

Continue reading "The problem with plastic"

 

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.

 

 

 

 

 

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.

 

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.

 

 

 

                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.

 

 

 

 

Continue reading "What is Plastic?"

               The Incas established a mighty empire that stretched along the Pacific coast of South America. The early rulers defeated the other tribes of Cuzco. The early kings were called Sinchi. It was only from the rule of the sixth ruler, Inca Roca that they called themselves Inca. The eighth Inca. Huiracoch conquered most of Urubamba Valley, in the fifteenth century. During an attack on the enemy Chanka his son Pachacutec Yupanqui seized power. Pachacutec was called ‘he who remakes the world’. He recorded the history of his people.

               His son Tupac Yupanqui was a patron of art and science. He led the empire to its golden age, and extended his rule as far as Chile and Ecuador. His son Huayana Capac conquered parts of Colombia.

 

               The pharaohs of Egypt conquered Kush around 2000 BC. Kush, also known as Nubia, is present day Sudan. Kush freed itself from the clutches of the pharaohs during the period of the Hyskos from 1650 to 1540 BC. However, Kush again came under Egyptian rule from 1540 BC. An Egyptian viceroy governed Kush from Aniba. Nubians were skilled fighters and were highly valued as soldiers in the Egyptian army. The Kushites cashed in on the weakening of Egyptian authority, and set up their own kingdom in Napata. The Kushite rulers turned the tables on Egypt. From the reign of King Piye, in the eighth century, Egypt came under their rule. They were known as ‘Black Pharaohs’.

               During the reign of Tahrqa, they were driven out of Egypt by the Assyrians, and they withdrew into Napata. King Ergamenes I founded a new dynasty between 270 and 260 BC. Meroe was the capital of the new kingdom. The kingdom of Meroe experienced its golden age under King Natakamani. The Romans razed Napata to the ground in AD 279. However, the kings and queens of Napata bounced back from defeat, and beat back the Romans. A Nubian nomadic people called Blemmyes took over the rule of Meroe in 250 AD. Meroe was destroyed around AD 350. 

                    The wise King Solomon and the Queen of Sheba had a son called Menelik I, according to Ethiopian legend. King Menelik I was the first king of Ethiopia. Ethiopia is one of the world’s oldest states. Axum was the capital. Ethiopia’s power rose again under the Zagwe dynasty. Roha was made the new capital. The emperors bore the title of ‘Negus Negest’ meaning ‘king of kings’. Yekuno Amlak reestablished the rule of the Solomonic dynasty.

                    After 1493, the Portuguese were allowed into the country. The Portuguese helped the Emperor Claudius to stop the expanding kingdom of Adal. However, the Portuguese were thrown out of Ethiopia by Emperor Fasilidas in the seventeenth century. 

 

               Ghana was the first West African kingdom. It was formed around 750 BC. Mali, then known as Audaghost and Mauritania known as Kumbi Saleh were both part of the Ghana kingdom. Later, the Berber dynasty from the coast of Senegal conquered Audaghost and Kumbi Saleh in the eleventh century. Ghana fell.

               The Mandinka tribes of Mali made themselves independent. They set up their own kingdom with Niani as its capital. Sundiata Keita, the founder of the kingdom took the title of ‘Mansa’ or king of kings. The Kingdom of Songhai replaced Mali around 1375 AD. The conqueror Sunni Ali occupied Djenne and Timbuktu. In 1591, the kingdom was conquered by the Sultan of Morocco. The Hausa and Banza states rose in the area of present day Nigeria, Niger and Chad. 

               Have you heard of Zimbabwe? Zimbabwe means ‘great stone house’. The centre of the early culture in Southern Africa is located in the present day countries of Zimbabwe and Mozambique. From the second century, this area became home to farmers called Shona.

              The fifteenth century saw the birth of a new empire in Zimbabwe. The empire was called Munhumutapa after its first ruler’s name. Shortly after 1480, the Munhumutapa Empire fell apart. Changa, a governor of the Munhumutapa Empire founded the empire of Changamire. It remained a political power until 1834.