Measuring Enthalpy Changes 0.0 / 5 ? ChemistryThermodynamicsInternational BaccalaureateOther Created by: Lotto65Created on: 26-02-17 19:39 Give a definition of energy The ability to do work (move a force through a distance) 1 of 29 What is the unit of energy? Joules 2 of 29 Energy = Force x Distance 3 of 29 What is given out when bonds are made? Energy 4 of 29 What is required to break bonds? Energy 5 of 29 What is the most important type of energy in chemistry? Heat 6 of 29 In an exothermic reaction, are the bonds in the reactants or products stronger? Products 7 of 29 What is the principle of exothermic reactions? Heat is given out to the surroundings 8 of 29 Give two examples of exothermic processes Combustion and neutralisation 9 of 29 In an endothermic reaction, are the bonds in the reactants or products stronger? Reactants 10 of 29 What does it mean if the bonds in the reactants are stronger than the products? Heat is absorbed from the surroundings 11 of 29 What is enthalpy? The internal energy stored in reactants 12 of 29 Can we ever know the absolute value of an enthalpy or the enthalpy of the products? No 13 of 29 What can we measure in terms of enthalpy? The difference in enthalpy between the reactants and products 14 of 29 What value does an enthalpy have if it is an endothermic reaction? Positive 15 of 29 What value does an enthalpy have if it is an exothermic reaction? Negative 16 of 29 What sort of conditions are enthalpy changes given in? Standard conditions 17 of 29 What defines a standard condition? 100kPa pressure and 298K temperature 18 of 29 In an endothermic reaction, are the reactants or products more stable? Reactants 19 of 29 In an exothermic reaction, are the reactants or products more stable? Products 20 of 29 What is heat? The total amount of energy in a certain amount of substance 21 of 29 What does heat depend on? The amount of substance present 22 of 29 What is temperature? A measure of the 'hotness' of a substance. The measure of the average kinetic energy present in a substance 23 of 29 Does temperature rely on the amount of substance present? No 24 of 29 What piece of equipment can measure enthalpy change experimentally? Calorimeter 25 of 29 The heat produced in a calorimeter in an exothermic reaction is used to do what? Raise the temperature of the water (known mass) 26 of 29 How can we calculate the heat transferred from the water to the reaction in a calorimeter? Measure the lowering of temperature 27 of 29 Why do we need to extrapolate temperature - time graphs for calorimeter experiments? Some heat would have been lost to the surroundings so the results are not accurate. We can see the temperature rise if the reaction was instantaneous. 28 of 29 Give two ways you can prevent heat loss to the surroundings with a calorimeter? Use an insulating material to contain the reaction mixture (polystyrene cup); Put a lid over the reaction mixture to prevent heat escaping upwards 29 of 29
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