Method: Weigh the burner, keeping the cap on to stop any alcohol evaporating, then place the measuring cylinder on the tripod with 150ml of water at room temperature in it. Take a starting temperature. Then using the burner, burn underneath for 3 minutes. At the end take the temperature of the water and replace the cap on top of the burner. Weigh the burner and record results. Repeat this for the other 3 burners.
Pre Testing: During my pre testing I found that when using ethanol the mass will go down with the temperature going up. These were the results I got
Diagram:
Research: By studying a range of reactions, the energy needed to make or brake any bond has been established. You can use these bond energies to predict whether any given reaction will be endothermic or exothermic. Melting and boiling are both endothermic processes, as energy must be put in to break the interparticle forces. The relatively high figures for water reflects the high energy needed to overcome the unusually strong forces between the water molecules. When a fuel burns, it reacts with the oxygen in the air to give waste gases in a combustion reaction. During this reaction the fuel is oxidised. More importantly, the reaction gives out heat energy. Which means that combustion reactions are strongly exothermic. If there is not enough oxygen to go around, the carbon is not fully oxidised to give carbon dioxide. Instead colourless, odourless but deadly poisonous carbon monoxide gas is produced. The flame should be like a miniature roaring bunsen flame.
In an exothermic reaction:-
- Temperature increases
- Loses heat to surroundings
- Breaking bonds takes in energy, making bonds release energy
- In an exothermic reaction more energy is released from making bonds than is taken in breaking bonds
Prediction:
Methanol:- 2CH4O + 3O2 = 2CO2 + 4H20
3 X C – H = 412 X 3 = 1236
1 X C – O = 358
1 X O – H = 463
2057 X 2 = 4114
4114 + (496 X 3) = 2 (2 X 743) + (8 X 463)
5602 – 6676 = - 1074
Ethanol:- C2H6O +3O2 = 2CO2 + 3H2O
1 X C – C = 348
5 X C – H = 412 X 5 = 2060
1 X C – O = 358
1 X O – H = 463
3229
3229 + (496 X 3) = (2 X 743) + (6 X 463)
4636 – 5750 = -1114
Propanol:- 2C3H8O + 9O2 = 6CO2 + 8H2O
2 X C – C = 696
7 X C – H = 2884
1 X C – O = 358
1 X O – H = 463
4401 + (9 X 496)
4401 + 4464 = 8916 + 3704
8865 – 12620 = -3755
Butanol:- C4H10O + 6O2 = 4CO2 + 5H2O
3 X C – C = 696
9 X C – H = 3708
1 X C – O = 358
1 X O – H = 463
5225 + 2976
8201 – 10574 = -2373
As the length of the carbon chain increases the energy produced also increases.
