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SQA National 5 Chemistry Endothermic & Exothermic

Endothermic & Exothermic

This page covers the following topics:

1. Loss of energy
2. Energy change of reactions
3. Determining energy changes

Energy is conserved in reactions, meaning it is never created or destroyed but rather transferred to or from a reaction environment. Energy is gained and lost from a reaction mixture as bonds are broken or made.

Loss of energy

If a reaction gives out heat it is exothermic and if it draws in heat it is endothermic.

Energy change of reactions

Experimentally you can determine if a reaction is endothermic or exothermic by checking for energy given out or taken in. Simply this can be done by feeling the reaction container or using a thermometer for heat change, and observing any light energy given out.

Determining energy changes

1

In the reaction between citric acid and sodium hydrogencarbonate the energy of the surroundings drops by 4 degrees celcius, is this exothermic or endothermic?

In the reaction between citric acid and sodium hydrogencarbonate the energy of the surroundings drops by 4 degrees celcius, is this exothermic or endothermic?

2

Does the reaction profile diagram shown show an endothermic or exothermic reaction?

Does the reaction profile diagram shown show an endothermic or exothermic reaction?

3

Oxidation reactions, including combustion, usually heat up their surroundings are they endothermic or exothermic?

Oxidation reactions, including combustion, usually heat up their surroundings are they endothermic or exothermic?

4

When hydrochloric acid is neutralised with sodium hydroxide in a polystyrene cup you can feel the temperature of the cup increase, is this endothermic or exothermic?

When hydrochloric acid is neutralised with sodium hydroxide in a polystyrene cup you can feel the temperature of the cup increase, is this endothermic or exothermic?

5

Suggest in what form energy may be lost from a reaction mixture?

Suggest in what form energy may be lost from a reaction mixture?

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