Mixtures
Although you do not realise it, you meet quite a few mixtures in the course of a day. If you have a shower in the morning, the first mixture you meet is one made from shower gel and water. It forms soapy bubbles which clean your skin. The water that flows from your shower is also a mixture - it contains water, shower gel and dirt. If you wash in a wash basin you still make a mixture - of water, soap and dirt.

At breakfast time you may drink a mixture and also eat one. Your coffee is a mixture of coffee grains, water, milk and perhaps also sugar. Your breakfast cereal may be a mixture of cereal grains, nuts and fruits all soaked in milk.

As you go to school you may pass a building site and see water, sand, lime and cement being mixed together to make mortar. This is used to stick bricks together in a wall. A lorry with a large drum turning on its back may also be there. Inside the drum water, sand, cement and gravel are being mixed to make concrete. If you pass any factories on your way to school the chances are that mixtures will be being made in them too. For example, glass is made from a mixture of sand, lime and soda while paper is made from a mixture of wood fibres, clay and wax. When mixtures are made on building sites and factories, they form new materials. By mixing substances and by treating them in some way, often by heating them up, a huge number of materials and products can be made. If you look on the label of your shower gel or your tube of toothpaste you will find a surprisingly large number of substances have been mixed together to make them.

When you get to school, you will find yourself using furniture made from mixtures. The plastic part of your chair is made from a mixture of substances to make your seat strong, well-shaped and maybe colourful. The table top, on which you work, may be made from a mixture of wood chips and glue. You could look underneath to find out.

Even on your way home from school you may come across more mixtures. This time you may recognise them - a mixture of sweets in the corner shop. You will use mixtures to pay for them. Coins are made from mixtures of metals called alloys. "Copper coins" are made from a mixture of copper, zinc and tin while "silver" coins are made from a mixture of copper and nickel.

Is a mixture a new material?
No. It is simply a mixture of different materials. Each material or substance in the mixture has its own properties. For example, if you mixed steel paper clips with flour you could easily separate them with a magnet. You could do this because both the steel and the flour keep their properties even though they are mixed together. Steel is magnetic so when a magnet is passed over the mixture the paper clips will spring to it. The flour is not magnetic and will remain unaffected by the movement of the magnet.

Are mixtures used to make new materials?
Yes, they are. Making a mixture is an important step in the process of making a new material. However once the mixture is made it has to be treated in some way to make the new material. This treatment will make the substances in the mixture change. When they have changed the new material is made. It has different properties from the original substances in the mixture. For example, sand, lime and soda are all powders that you cannot see through but from this mixture you can make a transparent sheet of glass.

How are mixtures changed into new materials?
Some mixtures, such as concrete, change as soon as water is added to them. Many mixtures, such as the mixture to make glass, need heat.

Are foods mixtures?
Many foods are mixtures. Some foods still remain mixtures even when they have been heated. In a vegetable stir-fry, for example, the onion, bamboo shoots, water chestnuts and bean sprouts are just heated together so they can soften and be easier to digest. They do not become some other food such as a vegetable pancake but remain separate. This means you can pick out each vegetable separately with your chopsticks.

When you dilute a drink do you make a mixture?
Yes. You add water to the fruit juice. Neither the water nor the fruit juice changes in any way. The water simply spreads out the fruit juice and makes it taste less strong. There is still the same amount of fruit juice present as there was before the water was added.

When water and salt are mixed is a new material made?
No. The salt has simply dissolved in the water. It has split up into tiny particles that you cannot see but it is still there mixed with the water. Dissolving is just a mixing process in which a substance breaks up into tiny particles to mix with a liquid.

Why are silver coins called silver coins if they do not contain any silver?
They used to contain silver but silver is too expensive to use today. Scientists who work with metals, called metallurgists, experimented with different mixtures of copper and nickel until they found an alloy which looked like silver.

Why do copper coins have other metals in them?
Copper is quite a soft weak metal and could not stand up to being passed from pocket to purse to till for many years. The other metals are added to make a tougher metal which will not wear away while the coin is in use.