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Is the Heat Energy Released On Combustion of an Alcohol Dependant On the Size of the Alcohol

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CHEMISTY SC1 IS THE HEAT ENERGY RELEASED ON COMBUSTION OF AN ALCOHOL DEPENDANT ON THE SIZE OF THE ALCOHOL PLANNING INTRODUCTION Many organic compounds are used as fuels. Most of the fuels used in the UK are hydrocarbons (Natural Resources: coal, oil, gas). Other countries make use of their own natural resources rather than important coal, oil or gas from abroad. For example, Brazil ferments its large sugar crop into alcohol, which it then mixes with petrol and uses as a fuel. Alcohols can be used as fuels when they are burnt they release heat energy. By measuring the heat energy released by burning a known amount of similar alcohols the effect of the size of the alcohol on the heat energy released can be determined. This energy is called the heat of combustion. Generally, a fuel is a substance, which is burned to produce heat energy. An exothermic reaction is a reaction which, gives out energy to the surroundings, usually in the form of heat and usually shown by a rise in temperature. ...read more.


4. State of fuel (solid, liquid, gas) - if the fuel is a gas it will burn much quicker than if it is a solid. 5. Impurities - Impurities will affect the outcome of the results because they elevate the boiling point (not all alcohols vaporize at the same temperature) 6. Size of molecule of alcohol. 7. Pressure - The more pressure there is the more difficult it is for the alcohol to vaporise and therefore doesn't burn as quickly. METHOD The method used is likely to be very similar to what is written below: 1. 100cm3 will be measured out. 2. The temperature of this will then be taken and recorded. 3. The weight of the alcohol and bottle will be measured and recorded. 4. This will then be put into the apparatus. 5. The wick will be lighted. 6. This will then be put into the metal stand and chimney. 7. It will be heated till the temperature rises by as close to 10 degrees Celsius as possible. ...read more.


The following table shows how many joules it takes to break each bond: C-H = 410 O=O = 498 H-H = 436 C=O = 743 C-O = 360 C-C = 350 O-H = 463 All of these energy values are measured in joules. From these we can judge how much energy is needed to break the bonds in the alcohols: Methanol = 2100 Ethanol = 3270 Propanol = 3740 Butanol = 4560 Pentanol = 5380 As shown above the longer the molecules get the more energy required to break the bonds. So we can say for example Pentanol will require more energy than Methanol simply because It has more bonds to break. These are only experimental values and it won't be exactly like this in the actual experiment because out equipment is not that accurate but it will be the same similar pattern. SECONDARY DATA M/g mol P/g cm n Tm/K Tb/K /kJ mol Methanol 32.0 0.793 1.3280 179.2 338.1 -726.0 Ethanol 46.1 0.789 1.3610 155.8 351.6 -1367.3 Propanol 60.1 0.804 1.3860 146.6 370.5 -2021.0 Butanol 74.1 0.810 1.3990 183.6 390.3 -2675.6 Pentanol 88.2 0.815 1.4100 194.1 411.4 -3328.7 ARIE RASHID 11DS ...read more.

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