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Burning alcohols to heat up a can of water

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Introduction

In this investigation I will be burning alcohol's to heat up a can of water. I will be burning four alcohol's, methanol, ethanol, propanol and butanol. The aim is to find out how much energy is produced when burning these alcohols. Alcohol's react with oxygen in the air to form water and carbon dioxide. The reaction that is involved in burning alcohols is exothermic because heat is given out. From this reason the reactant energy is higher than that of the product. The energy is given out when forming the bonds between the new water and carbon dioxide molecules. The amount of energy produced by such exothermic reactions can be calculated by using the formula Mass of the substance x rise in temp x SHC (specific heat capacity). The specific heat capacity is the number of joules required to heat one gram of water by 1�C. I chose to use water because it is safe, easily found, and has a reliable specific heat capacity of 4.2. I will also need to ensure that I conduct the experiments safely. As alcohol's are very dangerous and highly flammable I will wear my safety goggles at all times. ...read more.

Middle

I can come to predict that the longer the molecular structure in the alcohol the more energy it will take to remove the bonds. So when I come to predicting results I can safely say that Butanol will evolve more energy than methanol simply because it has more bonds to break. Results Starting temp (c) Finishing temp (c) Temp difference Methanol 24 29 4 Proponal 20 29 10 Butanol 19 28 11 Ethanol 22 29 8 Repeat readings Starting temp (c) Finishing temp (c) Temp difference Methanol 23 26 6 Proponal 21 30 8 Butanol 20 30 9 Ethanol 21 29 8 Average results Alcohols Starting temp (c) Finishing temp (c) Temp difference Methanol 22 27 5 Proponal 20.5 29 9 Butanol 19.5 29 10 Ethanol 21.5 29 8 Table showing the temperature change compared to the amount of carbon atoms in each alcohol Alcohols Number of carbon atoms Temperature change (c) Methanol 1 5 Ethanol 2 8 Propanol 3 9 Butanol 4 10 Amount of energy produced from each alcohol Energy = Mass of water x 4.2 x Rise in Temperature Methanol E = 150 x 4.2 x 5 = 3150 kj Ethanol E = 150 x 4.2 x 8 = 5040 kj Propanol E = 150 x 4.2 ...read more.

Conclusion

This was a very difficult experiment to conduct in a classroom because there are lots of potential ways of losing heat because everything likes to gain heat energy. I think the thing that hindered our results the most was the fact that gusts of air and convection currents were taking the heat away from the experimental area and there was no way to stop this. Perhaps if I started the experiment below room temperature, so that the amount of gained energy, from room temperature, might equal the energy lost at temperatures higher than room temperature, then the experiment could produce better results. If there is a limited supply of oxygen then you get carbon monoxide (each carbon atom can only bond with one oxygen atom). This is when incomplete combustion has occurred. This is so because the carbon monoxide could react some more to make carbon dioxide. If the oxygen supply is very limited then you get some atoms of carbon released before they can bond with any oxygen atoms. This is what we call soot. Since heat is given out when bonds form, less energy is given out by incomplete combustion. So this is why it affects the outcome of the experiment. To overcome this problem, I would have to make sure a sufficient supply of oxygen was involved in the reaction. ...read more.

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