- The distance from the wick to the beaker containing the water to be heated (If you altered the distance then the water would be heated quicker the less distance there was from the wick to the beaker)
Fair Test: In this experiment I will have to keep the following factors the same to ensure a fair test:
- Amount of water used each time
- Width of wick
- Diameter of beaker containing water
- The temperature water is heated to
- The distance from the which to the beaker containing the water to be heated
Plan: For this experiment I will require the following:
- A beaker
- Alcohol burner
- Water
- Matches
- Heat proof mat.
- Retort stand
- Ruler
- Thermometer
- Methanol
- Ethanol
- Propanol
- Butanol
Set up the equipment as shown. For the first set of result, place one of the 5 different alcohols into the alcohol burner and then light the wick and record how much the alcohol burner weighed before it was lit and then after the temperature of the water being heated rose 30°C. Repeat this process but with a different alcohol from the set of 5 each time. This data gathered will then be Set 1. To get set 2, the process needs to be repeated for all 5 alcohols again. To find out how much energy is in each alcohol using the results just gathered we first use the following equation: MCθ
M = Mass
C = Specific heat capacity of water which is a constant 4.2
θ = Temperature difference of water (the temperature you are allowing the water to be heated by)
E.G. 100g x 4.2 x 30°C = 12600j
We then use the following formula to work out the energy produced:
Grams of burnt alcohol=6g (To work out how much alcohol has be burnt you subtract the weight before the wick was lit and then after the temperature of the water had been heated by 30°C.)
Mr of Methanol=32
6 divided by 32 = 0.1875
12600j divided by 0.1875 = 67200j
67200j divided by 1000 (to convert the number into Kj)=672Kj
Analysis: From out experiment we found out that the more carbon and hydrogen atoms each alcohol has in its formula, the more energy is produced when the alcohol is burnt. This can be shown from the data we collected:
As you can see, the results confirm the prediction that the more carbon and hydrogen atoms the alcohol contains, the more energy is released from the alcohol when burnt. This is because when bonds are formed, energy is given off, therefore as more carbon dioxide and water is being produced, more energy is being released. My results show this as the Kj of energy produced when the alcohols are burnt increases for each alcohol which contains more carbon and hydrogen atoms in its formula.
Evaluation: I believe that the method we used to obtain evidence was not a very efficient or accurate one, this is because it allowed heat energy to escape into the surrounds to ensure this doesn’t happen, we could use a system called a calorimeter which makes sure as much as the heat as possible produced from the burning alcohol, is used to heat the water. To produce better results we could also measure the temperature with a computer. Another issue is measuring the water that is going to be heated. If we were to measure 100ml of water with a 5ml measuring cylinder, then each time we measured 5ml, we will incur a small error, therefore measuring 10 x 5ml to get 5ml will induce a large error as the errors produced each time 5ml is measured out will mount up to produce one large error. Therefore is a 100ml measuring cylinder is used, you only need to measure 100ml out once, therefore only inducing a small error.
I believe that some of the evidence we gathered is not accurate, I believe that the evidence gathered for butanol is inaccurate, this is because when the average of the set of data is calculated and then plotted on a graph with the rest of the alcohols, it does not fit on the line that is produced when the first 3 alcohols have a line drawn through them. Discounting the anamolie of the results gathered for butanol, we could continue the line of the graph and use it to find out the energy contained in other alcohols such as hexanol. This can be done by knowing hexanol’s Mr and then tracing a line from the Mr of hexanol to the line that is produced when we link the first three results of the alcohols on the graph. When the Mr meets the line then follow a line downwards and the line will point to an energy value for that Mr, that energy value will be close to hexanols energy value.
