Energy Changes

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AQA Chemistry Further

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crinklechips1
Created by crinklechips1 over 5 years ago
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Energy Changes
1 Exothermic reactions
1.1 Energy change is always negative - Energy always released to surroundings
1.2 Eg. combustion
1.3 Bond making
1.4 More energy is released making bonds than is taken in breaking bonds
1.4.1
2 Endothermic reactions
2.1 Energy change is always positive - energy is taken in from surroundings
2.2 Eg. Creating quicklime, Baking a cake
2.3 Bond breaking
2.3.1
2.4 More energy is required breaking bonds than is released making bonds.
3 Activation Energy
3.1 Required to break the bonds in the reactants
3.1.1
3.2 Minimum energy particles need to react
4 Catalysts
4.1 Speed up a reaction by lowering the activation energy
4.1.1
5 Q = mc ΔT
5.1 Q = the heat energy transferred (joule, J)
5.1.1 m = the mass of the liquid being heated (grams, g)
5.1.1.1 c = the specific heat capacity of the liquid (joule per gram degree Celsius, J/g°C)
5.1.1.1.1 ΔT = the change in temperature of the liquid (degree Celsius, °C)
6 Measuring Energy Transfer
6.1 1.Measure cold water into the CALORIMETER 2.Record the starting temperature of water 3.Heat water using flame from the burning fuel 4.Record final temp. of water
6.1.1 To reduce heat loss - Increasing accuracy: Use a lid, Insulate around the beaker, stir, prevent draughts
7 Fuel Effects: -Burning fuels releases CO2, causing global warming which is expensive to slow down and develop alternatives -Crude oil is running out and gets more expensive
8 Energy released in Joules
8.1 Energy Change per Mole: 1.Energy released 2.Find moles of substance (mass/mr) 3.Energy released/Mol