And the products of oil and gas refineries were hydrocarbons, containing exactly the kind of molecules that could join up to make plastics. 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. VOICEOVER: The particles that make up gases and liquids move randomly. This movement allows the action of diffusion to happen. After we’ve removed all the water from the solution, there’s only salt left behind and this is pure water. Cel: Ah, OK. So, do different compounds react in different ways when we're trying to extract the metal from them?

VOICEOVER: Zach has a bowl of ice cubes with a mass of five hundred grams. After some time the ice cubes melt, but the scales still show five hundred grams. This is because melting the ice has not created or destroyed any atoms and the mass has stayed the same. This is known as the law of conservation of mass. It applies to both chemical reactions and physical changes. At room temperature, the water contains a certain amount of dissolved gases from the air. The water straight from the tap creates cloudy ice cubes because these gases that were dissolved in the water form tiny bubbles in the ice. 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. The filtered liquid is called the filtrate. The larger solid particles, in this case, the sand grains are unable to pass through and are left on the paper. And we call this the residue.Katie: That's amazing. So, when water freezes it makes the atoms rearrange themselves so the result is the ice. But, because atoms can't be destroyed, the ice still has the same amount of stuff in. It just looks completely different. Ben: OK, here we go. I'll take the lid off. OK, there we go. Take a look at that. Now it's not a clear solution, is it? So, would we define the sand as insoluble in water? 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: Put some water into your beaker just deep enough that the very end of the paper goes into the water.

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.

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Miss Armit: No, not quite. They move round differently in each one. So in gases they are far freer to move around than in liquids and in solids. They have a lower density and they're far apart. In solids they're much closer together and they can only vibrate. And liquids are kind of in between. Their particles are spread out randomly and their density is less than the solids, but higher than gases. Dr. Tim: Right. Now, filtration is the process by which you remove an insoluble solid from the liquid. How's that going, Ben? Miss Armit: So, it happens mainly liquids and gases. This is because the particles can freely move around. It doesn't really happen in solids as the particles are in this fixed position and they can only vibrate on the spot. The particles are really whizzing about in the water, and they’re escaping into the air, or evaporating, faster than ever. 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.

Before long, the water level drops. Even after we take the heat away, the liquid continues to evaporate, leaving crystals of salt behind.Mrs Roberts: Yeah. So, a displacement reaction involves a metal and a compound of a different metal. In a displacement reaction a more reactive metal will displace, which means pushes out, a less reactive metal from its compound.