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Chemical Reactions ©TCL Chemical Reactions ©TCL Keyword Definition Endothermic Reactions Oxidation Reactions In an endothermic reaction, thermal energy is taken in from the In an oxidation reaction, a substance gains oxygen. Metals and Endothermic Reactions that take in heat surroundings, therefore there is a temperature decrease. Thermal non-metals can take part in oxidation reactions. decomposition is an example. Metals react with oxygen in the air to produce metal oxides. For Exothermic Reactions that give out heat Exothermic Reactions example, copper reacts with oxygen to produce copper oxide In an exothermic reaction, thermal energy is given out to the when it is heated in the air. surroundings, therefore there is a temperature increase. Oxidation Reaction of other elements with oxygen Combustion, oxidation and neutralisation reactions are all examples. Copper + Oxygen → Copper Oxide 2Cu + O → 2CuO Temp decrease decrease Temp 2 → Combustion Burning fuel in oxygen Thermal Decomposition Thermal When a substance is broken down into 2 or Some compounds break down when heated, forming two or more Decomposition more products by heat products from one reactants. → Temp increase increase Temp Many metal carbonates can break down easily when it is heated: Reactivity series List of metals in order of reactivity Copper Carbonate → Copper Oxide + Carbon Dioxide Displacement A more reactive metal will displace a less Combustion Copper carbonate is green, copper oxide is black. We can test for reactive metal from its compound Combustion is another name for burning. It is an example of an carbon dioxide using limewater. Limewater is colourless, but turns exothermic reaction. There are two types of combustion – complete cloudy when carbon dioxide is bubbled through it. Catalyst A substance that increases the rate of a combustion and incomplete combustion. reaction but is not itself used up. Reactivity Series Complete Combustion Some metals are very Polymer Long chain molecules made up of many Coal, oil and gas are furls. They contain hydrocarbons (compounds unreactive. This means they monomers. of hydrogen and carbon atoms only). When these fuels burn, it don’t take part in chemical reacts with oxygen in the air to produce carbon dioxide and water Fuel Contain hydrocarbons – compounds reactions. For example platinum. vapour. containing hydrogen and carbon atoms only. Some metals are very reactive Fuel + Oxygen → Carbon Dioxide + Water and they take part in chemical Activation The minimum amount of energy that colliding reactions easily to form new Energy particles must have for them to react Incomplete Combustion substances. If there is not enough oxygen in the air for complete combustion, incomplete combustion will happen instead. Further Reading: This time either carbon monoxide is produced (a toxic gas which can https://www.bbc.com/bitesize/guides/zqd2mp3/revision/3 lead to death) or carbon is produced (appears as soot and smoke https://www.bbc.com/bitesize/articles/zcwxcj6 which can cause breathing problems). https://www.bbc.com/bitesize/guides/zqd2mp3/revision/5 Fuel + Oxygen → Carbon Monoxide + Water Displacement Reactions https://www.bbc.com/bitesize/guides/zqd2mp3/revision/6 Fuel + Oxygen → Carbon + Water Displacement reactions involve a metal and a compound of a different metal. In displacement reactions, a more reactive metal Catalysts will displace a less reactive metal from its compound. Magnesium + Copper Sulfate → Magnesium Sulfate + Copper A catalyst is a substance that: Magnesium is • Speeds up the rate of a chemical reaction more reactive than • Does not alter the products of the reaction copper, so it • Is unchanged chemically and in mass at the end of the reaction. displaces (pushes out) the copper Catalysts provide an alternative reaction pathway that has a lower within the activation energy than the uncatalysed reaction. compound. .
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