Topic 8: Energy changes in chemistry Flashcards
Reactions can be classified as either …
Exothermic or endothermic
What are exothermic reactions
reactions which give out heat energy. Energy change for exothermic reactions will be negative as it has lost energey to its surroundings
What are endothermic reactions
Reactions which take in heat energy.
Positive energy change as it has gained energy from its surroundings.
What is activation energy
Minimum amount of energy required for a reaction to occur.
What is combustion
something burns in oxygen. When a fuel burns heat energy is given out
What is neutralisation reaction
An acid and an alkali react to form salt and water
What is a displacement reaction
More reactive metal displaces a less reactive metal from compound.
What is rusting
Exposed to air and water to form hydrated iron oxide
What is hydration
When water is added to an anhydrous salt it forms the hydrated sal
E.g. anhydrous copper sulphate is white and turns to blue in water.
What are the endothermic reactions
activation energy
combustion
Neutralisation
Displacement
Rusting
Hydration
What is thermal decomposition
Breakdown of a compound using heat
Formula for thermal decomposition
Metal carbonate -> metal oxide + carbon dioxide
What are the exothermic reactions
thermal decomposition
What is breaking bonds in terms of energy
Requires energy and is an endothermic process
What is making bonds in terms of energy
Gives out energy. it is an exothermic process
How to work out the energy change for a reaction
adding together energy needed to break bonds with energy given out when bonds are formed
