With the proliferation of the motorcar and expansion of industry and cities, enormous quantities of oil and gas were being pumped out of the ground and processed into fuel. Gethin : What about diffusion? Can happen in all states? And by that I mean solids, liquids and gases? A balanced equation gives more information about a chemical reaction because it includes the symbols and formulae of the substances involved. There are two steps in writing a balanced equation:

Mrs Roberts: Yes. So if we were to categorise metals by their reactivity, the most reactive metal would naturally be at the top. So, if I'm going to test you now. So, if a copper is added to a solution of magnesium chloride no reaction occurs. What does that tell you about the reactivity between copper compared to magnesium? I’ll put the salt solution in an evaporating basin, and use a heat source like a Bunsen burner to gently increase the temperature of the water. Dr. Tim: Right. Now, filtration is the process by which you remove an insoluble solid from the liquid. How's that going, Ben? Miss Roberts: So, it may look like the mass has increased, because the ice takes up more room than the liquid water. But, the mass has in fact stayed the same. Now, here we go. I don't know if you can see, but the container now contains style slightly clearer water at the bottom. And left in the filter paper here at the top, if I show you, is loads of the sand. Look at that, most of the grains are there and it's filtered through to the bottom.

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This is unbalanced because there is one copper atom on each side of the arrow, but two oxygen atoms on the left and only one on the right. By heating the water to boiling point, we have decreased the solubility of the dissolved gases. They come out of the solution as bubbles and the remaining water has less gases dissolved, so is less cloudy. We are going to use chromatography to separate these different food colourings into the coloured pigments they are made from.

Draw a horizontal line with a pencil and ruler about 1 cm above the bottom of a piece of chromatography paper. Solutions are a mixture in which a solid or a gas has completely dissolved in a liquid. We called the solid a solute and the liquid a solvent. A solid that will not dissolve in a specific liquid is described as insoluble. Only handle the heater by the outer casing. Where possible, avoid handling the heater once it is switched on. Give the heater time to cool after it is switched off. In the example above (the reaction between copper and oxygen to make copper oxide), we get this in the first step: Miss Roberts: It does. And I want to show you what happens when a chemical reaction takes place or when there is a physical change in something that the mass stays the same. It is what's called 'conserved'.You will notice that the paper absorbs the water and it rises up the chromatography paper past the spots of food colouring. When the water reaches the spots, the pigments will dissolve in the water and move up the paper. This happens because some pigments are more soluble than others. The more soluble the pigment is, the longer it stays dissolved in the water and the further it travels up the paper. Teacher: The addition of the salt has made the ice a few degrees below freezing. The water in the milk changes state and turns from a liquid into a solid, turning it into delicious ice cream.

Carefully lower your paper into the water, letting the glass rod balance on the rim of the beaker. Make sure the pencil line is above the surface of the water. And in one of those great moments in history where knowledge and opportunity coincide, scientists realised that a vast source of raw ingredients for these new plastics had already been discovered.

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Katie: Wow. That's amazing. That's blown my mind, Miss Roberts. It really has. Here's a couple more examples to prove it too. Dr. Tim: That's called the filtrate. And the filtrate is slightly clearer than before, though, it is still a little bit cloudy. And that's because some of the smaller pieces of sand have managed to pass through the filter paper into the water. For example, sand is insoluble in water. We can separate insoluble solids from a solution using filtration. Filter paper has thousands of tiny holes that allow the liquid molecules to pass through. See, in this salt solution there are water molecules and salt particles all mixed together. The particles in a liquid are constantly jiggling around, and the warmer the liquid is, the faster they’ll move. Dr. Tim: That's exactly right, Ben. A substance is classed as insoluble if it does not fully dissolved in a specific solvent - in this case it's the sand is insoluble in water. Now, why don't you try and filter out that sand from the water.