C5 Energy Changes 0.0 / 5 ? ChemistryEnergy of reactions/Exothermic and endothermic reactionsGCSEAQA Created by: MissAmbageCreated on: 10-02-23 12:23 What is the law of conservation of energy? Energy cannot be created or destroyed only transferred usefully, stored or dissipated. 1 of 25 What is an exothermic reaction? Transfers energy from the reaction to the surroundings 2 of 25 What happens to the temperature during an exothermic reaction? Temperature increases 3 of 25 What are examples of everyday exothermic reactions? Self-heating cans and hand warmers 4 of 25 What is an endothermic reaction? Energy is transferred from the surroundings to the reaction. 5 of 25 What happens to the temperature during an endothermic reaction? Temperature decreases. 6 of 25 What are some examples of endothermic reactions? thermal decomposition and reaction of citric acid with sodium hydrogencarbonate. Also sports injury packs. 7 of 25 What is the activation energy? The minimum amount of energy that particles must have to react. 8 of 25 How can chemical reactions occur? When reacting particles collide with each other and with sufficient energy. 9 of 25 What do reaction profiles show? The relative energies of reactants and products, the activation energy and the overall energy change of a reaction 10 of 25 What happens to energy when bonds are broken? Energy must be supplied to break bonds. 11 of 25 What happens to energy when bonds are made? Energy is released when bonds are formed. 12 of 25 How do you work out the overall energy change of the reaction The difference between sum of energy needed to break bonds, and the sum of energy released when bonds are formed. 13 of 25 If the energy released from forming new bonds is greater than the energy needed to break existing bonds then the reaction is... Exothermic 14 of 25 If the energy needed to break existing bonds is greater than the energy released from forming new bonds than the reaction is... Endothermic 15 of 25 What do cells contain which produces electricity? Chemicals 16 of 25 What is voltage produced by a cell dependent on The type of electrode and electrolyte 17 of 25 How can a simple cell be made? Two different metals in contact with an electrolyte 18 of 25 What are batteries? Two or more cells connected together in series to provide greater voltage 19 of 25 Why do non-rechargeable cells and batteries stop working? One of the reactants has been used up and therefore chemical reactions stop. 20 of 25 What type of batteries are non-rechargeable? Alkaline batteries 21 of 25 Why can rechargeable cells and batteries be recharged? The chemical reactions are reversed with an external electrical current. 22 of 25 What are fuel cells supplied with? A source of fuel (eg hydrogen), oxygen and air. 23 of 25 How does the fuel cell produce a potential difference? Fuel is oxidised electrochemically within the cell. Oxidation of hydrogen to produce water. 24 of 25 Why may we use hydrogen fuel cells? Offering an alternative to rechargeable cells and batteries. 25 of 25
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