Heat Energy Changes in Chemical ReactionsEdexcel GCSE Chemistry: Flashcards

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Define an exothermic reaction.

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Define an exothermic reaction.: A reaction that gives out heat energy to the surroundings, increasing their temperature.
Define an endothermic reaction.: A reaction that takes in heat energy from the surroundings, decreasing their temperature.
Name four types of change where heat energy changes can be measured as a temperature change.: Salts dissolving in water, neutralisation, displacement, and precipitation reactions.
Is breaking bonds exothermic or endothermic?: Endothermic — it requires an input of energy.
Is making bonds exothermic or endothermic?: Exothermic — it releases energy.
When is an overall reaction exothermic, in terms of bond energies?: When more energy is released forming bonds in the products than is required to break bonds in the reactants.
When is an overall reaction endothermic, in terms of bond energies?: When less energy is released forming bonds in the products than is required to break bonds in the reactants.
How do you calculate the energy change of a reaction using bond energies?: Energy change = energy to break bonds in reactants minus energy released making bonds in products.
Define activation energy.: The minimum amount of energy that particles must have when they collide for a reaction to occur.
On a reaction profile for an exothermic reaction, where are the products relative to the reactants?: At a lower energy level than the reactants.
On a reaction profile for an endothermic reaction, where are the products relative to the reactants?: At a higher energy level than the reactants.
On a reaction profile, from where is activation energy measured?: From the energy level of the reactants up to the peak of the hump.