Darius Atashroo 5MR
Chemistry Coursework
Investigating the different amounts of heat given off by different alcohols in spirit burners when used to warm water
Planning Stage
In this piece of coursework, I am going to investigate the amount of heat produced when different types of alcohol are burned in spirit burners. I will compare the amounts of heat given off by the alcohols Ethanol, Methanol, Propanol and Butanol.
There are a number of factors that affect the amount of heat produced by the spirit burner, for example: the distance of the lit spirit burner flame from the beaker of water, the volume of water used, the exclusion of draughts, the mass of alcohol that starts off in the spirit burner, the size and type of the container used to hold the water and the time period for which the fuel is burnt. For my experiment, I have chosen to investigate the mass of the alcohol burnt. It is obvious that these reactions are exothermic, as they produce heat on burning and therefore cause a temperature increase in the water in this experiment. I will prove this in my prediction. I also know that there is a link between the number of carbon atoms in the alcohols and the amount of heat that they produce on burning. From my preliminary experiment, I am aware that as the number of carbon atoms increase in the alcohol, the more heat given out by it when it is burnt. For example, from my Reference Book of Data photocopy with ‘standard’ results, I can tell that there is more heat given out by the alcohol Ethanol (C2H5OH) than the alcohol Methanol (CH3OH) when they are burnt. This is because there are more carbon and hydrogen atoms in Ethanol, therefore meaning that more chemical bonds need to made for the resulting product of carbon dioxide to balance the equation and as a result more heat is given off.
There are also a number of factors which I would need to keep constant, some to prevent heat loss. Firstly, I intent to keep the volume of water heated at 200cm3 by using a 100 cm3 measuring cylinder, filling it twice separately and pouring the contents into my beaker which can hold 250 cm3. This is because if I do not keep the amount of water the same, the experiment would obvious become an unfair test. The size and type of the container will be kept the same throughout the experiment to ensure a fair test, making sure that a wide base container is not used as it will cause heat loss. Also, to improve the reliability of my results, I will keep the distance between the flame and the beaker of water constant. I will go about doing this by using a ruler to make sure of the distance and a clamp and stand to secure the beaker in place. Another major factor which will need to be controlled is the exclusion of drafts. If there are drafts present during the experiment, without exclusion they could divert the direction of the flame, causing it to take longer than it would to heat up the water without the drafts present, therefore affecting the accuracy of my results. I will keep the drafts out therefore by firstly performing my experiment near the centre of the room, away from any sources such as windows, and secondly by using a cardboard draft excluder around the three sides of my experiment. Other smaller factors include: stirring the water using the large stem thermometer during the experiment to speed up the reaction, zeroing the top pan balance so that the weight is more accurately measured and cleaning the soot off the glass container between experiments using tap water and cloths so that it does not affect the heat transferral.
