C5 Flashcards
Exothermic reaction
Reaction which transfers energy to the surroundings (usually by heating)
How to know reaction is exothermic
Rise in temperature
Examples of exothermic reactions
- combustion
- neutralisation reactions
Everyday uses of exothermic reactions
- hand warmers - use oxidation iron in air with a salt solution catalyst to release energy
- self heating cans of coffee - use reactions between chemicals and their bases
Endothermic reaction
Reaction which takes in energy from surroundings
How to know reaction is endothermic
Fall in temperature
Most common type of reaction
Exothermic
Examples of endothermic reactions
- reaction between citric acid and sodium hydrogencarbonate
- thermal decomposition
Everyday uses of endothermic reactions
- sports injury packs - chemical reaction allows pack to become instantly cooler
Temperature changes practical
- place polystyrene cup surrounded by cotton wool (insulation) in beaker
- add 25cm³ HCL and record temperature with thermometer
- add 5cm³ of NaOH
- stir and record peak temperature
- calculate temperature change
- determine if reaction was exothermic or endothermic
- repeat experiment with different volumes of NaOH
Reaction profile
Diagram that shows relative energies of reactants and products in a reaction and how energy charges over the course of the reaction
Activation energy
Minimum amount of energy reactants need to collide with each other and react
Labels of reaction profile
- title - exothermic/endothermic
- axis - x-reaction progress y-energy
- reactants
- activation energy
- products
- energy released/absorbed
Where is activation energy label on reaction profile
From reactants to peak
Where is energy released/absorbed label on reaction profile
Level with reactants line to products
