 In this new section we're going to take a look at a field of chemistry known as kinetics. This is the study of how fast reactions go. This is known as their rate. Also what affects how fast they go and what occurs on a molecular level as a reaction occurs. In this first video we'll revise some material from Year 10. What factors can you change about a reaction that will change its rate? So think back to Year 10 where you had perhaps your first encounter with rates of reaction. You may have done some experiments where you varied the conditions of a reaction and had a look at whether that made the reaction go faster or slower. As long as you aren't changing the reaction itself, the factors that you can play around with are the concentration of a reactant that's in solution, the pressure if you've got a gaseous reactant, the temperature of the reaction, the surface area if you've got a solid reactant or if you have two immiscible liquid reactants, so an oil and a water that need to be shaken up together, the surface area between those two has an effect on the rate. And the final thing is the presence of a catalyst. We need to note here that although in most cases changing things like concentration, temperature and so on, won't actually change what products are being produced, only how fast they're being produced. But there are examples where this does happen, particularly in organic chemistry where unwanted side reactions can occur if you don't get the reaction conditions just right. A classic example of a change in products that's easy to replicate in the lab is the reaction between copper and nitric acid, not an organic reaction this one. If you add some copper to dilute nitric acid, one molar for example, then you get copper nitrate produced along with nitrogen monoxide gas and water. Nitrogen monoxide is colorless. But if you add the copper to concentrated nitric acid, 15 molar say, then the stoichiometry is different and we get nitrogen dioxide gas as a product. This is a brown toxic gas. And this is what you can see in the picture here from the Royal Society of Chemistry, the brown nitrogen dioxide gas coming off from the solution.