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Burning alcohols.

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Introduction

Chemistry Coursework - Laura Smythe Plan Preliminary Work For My preliminary experiment, I set up a tin can held up by a clamp and clamp stand. The bottom of the beaker was measured 10cm above the base of the clamp stand using a ruler.100cm3 of water was measured out into a 100cm3-measuring cylinder and emptied it into the tin can. A thermometer was placed into the beaker of water. An ethanol burner (including its lid) was weighed and the weight was recorded. The burner was then placed under the metal beaker on a heatproof mat. The ethanol burner was then lit, and the water was stirred constantly using the thermometer, whilst taking the temperature of the water. This was timed for two minutes, and then the temperature was taken again. After two minutes were up, the burner was blown out and the lid was put back on. Then the ethanol burner was weighed as before and the weight was again recorded. Here are the results: Weight Before Weight After Change in Weight Temperature Before Temperature After Change in Temperature 168.72g 167.64g 1.08g 19?C 41?C 22?C This information was then used in the equation to find the heat given out: Heat given out = Mass of water x 4.2 x Change in Temperature From the preliminary experiment I can work out that the ethanol burner transferred 9240 joules of energy. ...read more.

Middle

Joules I will repeat he experiment three times, as it will make my results more reliable, if I find any anomalous results, these will be repeated further. As this is a dangerous experiment, there are a lot of safety precautions that must be attended with. Unless the flame is lit, the lid must always be on the burner, as it will minimize errors and if any alcohol evaporates, it could lead to an explosion. The burner must always be placed on a heatproof mat when alight, so the bench does not burn, and when using ethanol, a Bunsen burner must not be alight near to it as the ethanol could catch fire. Fair Testing Fair testing is very important, it will help minimize errors and make my results more reliable. To make my experiment a fair test, the same equipment, temperature increase, height from the can to the stand base, mass of water will be used, and most importantly the burner will always be weighed with its lid on. The variable that will be changed it's the alcohol used. Obtaining Evidence Weight (g) (2dp) Alcohol Before After Decrease Average Ethanol 215.16 212.95 2.21 2.19 172.08 170.33 1.75 229.70 227.53 2.17 Propanol 190.20 188.20 2.00 2.01 196.26 194.25 2.01 194.21 192.59 1.62 Butanol 200.89 198.50 2.39 1.43 212.21 211.17 1.01 210.92 209.56 1.36 204.94 203.29 1.65 203.22 201.93 1.29 Pentanol 161.27 159.15 2.12 2.07 156.46 154.33 2.13 154.33 152.27 1.96 The highlighted experiments gave odd results and so have not been included in the average. ...read more.

Conclusion

I could further this experiment by investigating other homologous series, such as alkenes, or carboxylic acids. This would also me to see if there are any patterns or trends within the theory. To do this I would set up the same experiment, but instead of using alcohols, I would use the alkenes. To make the experiment more reliable I would use a wider range of fuels, for example, six. The first 6 alkenes are as follows: Ethane, Propene, Butene, Pentene, Hexane, and Heptene. Below are the relative formula mass and the formulas of the first 6 alkenes: Alkene Formula Relative Formula Mass Ethene C2H6 30 Propene C3H8 44 Butene C4H10 58 Pentene C5H12 72 Hexene C6H14 86 Heptene C7H16 100 Here are the Balanced Symbol Equations for the first six Alkenes: Ethene: 2C2H6 + 7O2 ? 4CO2 + 6H2O Propene: 2C3H8 + 10O2 ? 6CO2 + 8H2O Butene: 2C4H10 + 13O2 ? 8CO2 + 10H2O Pentene: 2C5H12 + 16O2 ? 10CO2 + 12H2O Hexene: 2C6H14 + 19O2 ? 12CO2 + 14H2O Heptene: 2C7H16 + 21O2 ? 14CO2 + 16H2O This would be a starting point for the experiment. I think I would find that the pattern is the same and that the longer the alkene, the more bonds contains. From what I have discovered in this experiment I would predict that Heptene would give out the most energy as the more bonds in the exothermic reaction the more energy given out from the reaction. ...read more.

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