Investigation on the combustion of Alcohols.

I will then repeat the experiment again two times so that I can get some replicated data, this then will then tell me whether I have any anomalies.

Fair test

To keep this experiment a fair test I will be keeping the wick an the same length because the bigger the quick the bigger that flame therefore this will give us a in accurate test. The distance from the flame to the beak will be kept at a constant distance because if you do not keep this at the same distance if you put it further away heat will lost to the surroundings. The same mass of water will be used for each alcohol and the same sized spirit burner will be used so that there is no heat loss. The water will be stirred constantly so that there is a constant heat transfer. I will place draft excluders around the experiment so that there is no draft for the heat to escape. To find the optimal mass of water I will conduct a preliminary experiment to decide this. To keep this a fair test we have to bear certain aspects in mind. The beaker of water must be the same shape because if it is not the flame may have more surface area of the area it has to heat. The alcohol must be weighed accurately with electronic scales that weigh up to, at least, two decimal points. While weighing the spirit burner, the burner must be covered to avoid the evaporation of the alcohol. The alcohol has to be weighed accurately before and after the experiment. The alcohol has to be blown out immediately when the water temperature has been raised 30 degrees; it must be covered after the experiment to avoid evaporation. The thermometer must be swirled around the water before a reading can be taken; this insures that you are measuring the temperature of the whole water not just the bottom of the beaker. The shape of the spirit lamp must stay the same and so must the wick length. If all this is done, we can ensure that we will get an accurate reading.

Safety Precautions

In order to ensure safety throughout the experiment I will wear safety goggles and make sure that the hot water is handled carefully therefore ensuring that there is no spills or burns.

Obtaining evidence

During the experiment, I obtained two sets of results, which will enable to have a wider range of results. During the experiment, I made sure that I wore safety

goggles and I handled the hot water with care.

The results I took are in the tables below. The temperature indicates the temperature of the beaker of water and the mass indicates the mass of the spirit burner before and after the experiment.

Constants that were kept:

During the experiment, I kept the length of the wick 1cm and the distance between the wick and the beaker was 10cm. The mass of the water was 100g the length of time was 100 seconds.

Ethanol

Starting temperature

7

7

End Temperature of Water

39

38

Temperature Change of Water

22

21

Starting mass

80.89

81.56

Ending Mass

78.06

79.09

Mass Change

2.83

2.47

Propanol

Starting temperature of Water

20

20

End Temperature of Water

45

43

Temperature Change

25

23

Starting mass

79.60

80.35

Ending Mass

76.50

77.23

Mass Change

3.1

3.12

Butanol

Starting temperature of Water

20

9

End Temperature of Water

48

45

Temperature Change

28

26

Starting mass

80.46

79.56

Ending Mass

76.80

75.93

Mass Change

3.66

3.63

Analysis

With these results I can now calculate the energy accumulate by the water, how ever this wont be accurate but it is the most suitable method of applying this data. I will first use this formula to calculate the energy gained by the water.

Mass of x specific heat x temperature rise = Energy gained by water

water(g) capacity(J/g/°C) (°C)

Ethanol

00 x 22 x 4.2 = 9240

Change in mass = 2.83 = 0.06152

Molar mass of Ethanol 46

9240 x 46 = 150190.81

2.83

50190.81 kJmol-1

Propanol

00 x 25 x 4.2 = 10500

Change in mass = 3.10 = 0.05167

Molar mass of propanol 60

0500 x 60 = 203225.81

3.10

203225.81 kJmol-1

Butanol

00 x 28 x 4.2 = 11760

Change in mass = 3.66 = 0.04946

Molar mass of Butanol 74

1760 x 74 = 237770.49

3.66

237770.49 kJmol-1

These are my replicated results for more accuracy:

Ethanol

00 x 21 x 4.2 = 8820

Change in mass = 2.47 = 0.053695

Molar mass of Ethanol 46

Heat Produced = 8820 x 46

2.47

64259.10 kJmol-1

Propanol

00 x 23 x 4.2 = 9660

Change in mass = 3.12 = 0.05200

Molar mass of propanol 60

93846.15kJmol-1

Butanol

00 x 26 x 4.2 = 10920

Change in mass = 3.66 = 0.05311

Molar mass of Butanol 74

221435.11 kJmol-1

The experiment went well there were no problems. My results I have been worked out above. With these results, I will plot a bar chart to represent this data graphically, and to see whether there is a trend. I have drawn graphs of the energy gained by water and also the Kjmol-1. These results are showed overleaf.

As you can see on my first set of data that the results are slightly inaccurate as it does follow a set trend that would indicate that energy that is given out is directionally proportionally to the carbon atoms which is what I had predicated. As you increase the carbons the energy output is greater this is proved my results however my results are not accurate

enough because they do not prove that the number of carbon atoms is not directionally proportional to the energy taken by the water.

As you can see from these results, the number of carbon atoms increases the energy in the water therefore increases, which then also increases the kjmol-1. from my results the

I can therefore conclude that as you increase the carbon atoms is the energy being put in should be the same as the energy been given out. The more carbon atoms there are the more energy that is given out this can be explained with the idea of bond energies.

The bonds between atoms require energy to be broken for example to break 1 mole of C-C bonds requires 348kj. We can say that bond energy of the C-C 348kj/mol. Therefore as you increase the carbon atoms the more energy you need to put in and the more energy that is given out.

This backs up my prediction and proves that my prediction was correct. I stated that as you increase the number of carbon atoms the more energy there is produced. Although my results are not completely accurate due to certain factor which allow for heat loss. However, my prediction was overall correct.

Evaluation

My experiment went well there were no problems throughout the experiment. My results followed my predicted trend. However, my results were not as accurate as possible, due to human error and certain factors that would make it easy for heat loss.

The experiment overall was not accurate, for example the thermometer and measuring cylinder could have been read wrong. Therefore wrong amounts and readings would have been taken. However, my results were accurate because they were both similar therefore meaning there were no anomalies.

The experiment could have been controlled inaccurately, is by human error, for example controlling the stop-clock and putting out the flame and covering the flame before evaporation could take place.

The experiment was not that suitable because heat loss could have escaped through the beaker and the heat would have evaporated therefore altering the mass of the water. Also, the water would have conducted through the beaker and also through convection through the surface of the water. And also, the water would have escaped through radiation. Then heat could have been lost through the flame as in my experiment there was a ten centimetre gap between the wick and the beaker, therefore heat loss could have been lost through that. Therefore, these factors made the experiment unsuitable.

I improvements I could have made to the experiment I would have made, is that I would insulate the beaker with foil and cotton wool to reduce the heat loss. Via conduction and radiation. I would place a lid over the beaker to stop evaporation and I would use digital thermometer to record the readings. I would use a pipette to measure the volume of the water this would therefore make it more accurate than a measuring cylinder. And also I would reduce the distance between the sprit burner and beaker to reduce the amount of heat lost.

To extend this investigation I would extend the range of alcohols used. I would use the next to after for example pentanol and hectanol and perhaps go as far as octanol. The prediction for that experiment would be the same as this one. As you increase the carbon atoms the more energy that is released.