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Comparing the heat energy produced by combustion of various alcohols

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Introduction

Comparing the heat energy produced by combustion of various alcohols Planning Introduction In this investigation I will be burning alcohols to heat up a beaker of water. I will be burning five alcohols, methanol, ethanol, propanol, butanol and pentanol. The aim is to find out how much energy is produced when burning these alcohols. 'An alcohol is a series of organic homologous compounds, with the general formula Cn H n + 1OH�. Alcohols 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. Form this reason the reactant energy is higher than that of the product. Equipment 1. Retort stand 2. Boss 3. Clamp 4. 250cm Conical 5. Thermometer 6. Tongs Chemicals 1. Methanol (Highly flammable) 2. Ethanol (Highly flammable) 3. Propanol (Highly flammable) 4. Butanol (Highly flammable) 5. Pentanol (Highly flammable). Safety As a safety, during the experiment, I have to wear a safety spec to protect my eyes, and an apron to protect my body. Also be very careful to the thermometer, because it has mercury inside. If it breaks, it may damage to our body. When I heating the measuring cylinder, I have to make sure the retort stand hold the measuring cylinder exactitude. ...read more.

Middle

� Weigh the spirit burner � Record all results The variables that must remain constant throughout the experiment are... � Mass of the water 100cm � Type of beaker, glass � Temperature rise of 30�C. � Surrounding temperature of around 23�C � The height of the beaker from the wick � Same set of scales � Weigh the spirit burner with the lid on. Diagram of the Experiment Obtaining Summary table Alcohols Average Temp Changes (?) Average Mass Used (g) Specific Heat Capacity Amount of Heat Energy RMM of alcohols Number of Moles Energy In 1 moles Methanol 32.8 1.39 4.2 13776 32 0.043 320372.1 Ethanol 31.7 0.99 4.2 13314 50 0.020 665700 Propanol 32.7 0.83 4.2 13734 76 0.011 1248545.5 Butanol 34.3 0.86 4.2 14406 74 0.012 1200500 Pentanol 32.3 0.77 4.2 13566 88 0.009 1507333.3 Here is the table of the results of the reaction on the comparing the heat energy produced by combustion of various alcohols Average table Alcohol Average Temp Change (?C) Average Mass Used (g) Methanol 32.8 1.39 Ethanol 31.7 0.99 Propanol 32.7 0.83 Butanol 34.3 0.86 Pentanol 32.3 0.77 Here is the table of the average result on the comparing the heat energy produced by combustion of various alcohols Here is the structure of the alcohols. Alcohols Structure Methanol CH3OH Ethanol CH3OH2OH Propanol CH3CH2CH2OH Butanol CH3CH2CH2CH2OH Pentanol CH3CH2CH2CH2CH2OH As you can see a longer molecule takes more energy to break its bonds, in this case Pentanol. ...read more.

Conclusion

This would give a better graph reading and a wider range of results to support a firm conclusion. On the other hand, if I had started below room temperature, so that the amount of energy gained, from room temperature might equal the energy lost at temperatures higher than room temperature. Next time reducing heat lost would be my main priority. Improving insulation techniques would be a valuable asset in obtaining the most reliable data I could. Another error is that of incomplete combustion. Complete combustion occurs if there are lots of oxygen atoms available when the fuel burns, then you get carbon dioxide (carbons atoms bond with two oxygen atoms). 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. Chemistry SC1 Marcus Ng 1 ...read more.

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