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Find out the difference in energy that is given out by the alcohols Methanol, Ethanol, Propanol and Butanol when they are burned under a tin of water for 3 minutes.

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Introduction

Robbie Morgan Alcohols Coursework Aim: The aim of this work is to find out the difference in energy that is given out by the alcohols Methanol, Ethanol, Propanol and Butanol when they are burned under a tin of water for 3 minutes. Plan: The first thing I need to do is to collect and correctly set up the apparatus. Here is a diagram of how I plan to do this: Here is the list of apparatus I am going to use: Stand, boss and clamp Spirit burner Metal can Thermometer Electronic scales Heat proof mat Matches I am going to use four different spirit burners each with a different alcohol in it. I am going to choose ones that look as if they have roughly the same amount of fuel in them to make the test fairer. I am using a metal can because it conducts heat better than a glass beaker and therefore it will give me a more accurate result. I will measure the temperature of the water to the nearest 0.5 of a degree because this is the smallest I can accurately measure with my naked eye on the thermometer available to me. I will use a stop clock to time 3 minutes for each experiment and I will also use the same amount of water each time (120 ml). In my preliminary work I discovered that 120 ml is the best amount because if you have less than that the water ...read more.

Middle

I think 3 minutes should be about the right time for this. Type of Alcohol - This is the factor I am going to change in order to answer my aim. Background science: An exothermic reaction is a reaction that gives out heat energy. The opposite to an exothermic reaction is an endothermic reaction, this takes in energy, and so is cold. The structure of an alcohol consists of Hydrogen, Oxygen and Carbon atoms. As you go down the list of alcohols you get more carbon and hydrogen atoms. For every carbon added there are two hydrogen atoms added. Combustion means to burn a substance in oxygen. In a reaction you get the same amount of product out as you do reactant going in. Therefore when writing the equation you need to balance both sides equally. We do this by making sure there are equal amounts of reactants and products on each side. Bond energy is how much energy it takes to make or break bonds between atoms. Prediction: Prediction: My prediction is as follows: I predict that the further towards the bottom of the table you go, the higher the energy released The unbalanced equation for Propanol C3H2OH + 02 --> CO2 + H2O The balanced equation is: C2H5OH+3O2 --> 2CO2 + 3H2O Below is what the molecule looks like: Here is the working out for energy per mol: C-H bonds 7x1= 7x412= 2884 C-O bonds 1x1= 1x360= 360 O-H bonds 1x1= 1x463= 463 O=O ...read more.

Conclusion

Evaluation: My results are quite reliable in that they went in a reasonably straight graph (see above). They were not really what I predicted though. I think My predictions were off because a lot of the heat escaped into the surrounding atmosphere. To make the experiment more accurate I would have used a thinner walled can. I also would have had some kind of shroud around the burner so that wind or disturbances could not have got to the burner and blown the heat away. I would also have had exactly the same amount of fuel in each burner as I think this makes a minute contribution to the results. I would also have used a more accurate heat measuring device, such as a digital thermometer. What I actually did in the experiment to attempt to keep it a fair test was to light the burner and blow it out exactly at the right time so that no more and no less heat energy got out. I also held the thermometer slightly away from the bottom of the tin so that it would not be directly influenced by the heat of the flame on the metal can. The only slight anomaly was for Propanol which was a bit lower that we expected. There are a few things that could have accounted for this, such as a person walking past and disturbing the heat flow, or a fellow scientist dropping water on the burner, or putting the flame out too soon. ...read more.

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