Therefore the larger alcohol molecules with longer carbon chains should release more energy because they contain more carbon and hydrogen atoms which produce more carbon dioxide and water molecules so releasing more energy.
Although these larger molecules should release more energy they also require greater amounts of oxygen. Air contains only 20% oxygen which is sometimes not enough to release all the chemical energy from the alcohol and can result in something called incomplete combustion when “soot” is produced.
Key factors and fair testing
Key factors:
- Mass of water
- Length of wick on the burner
- Type of alcohol
- Height of container (containing the water) above the flame
- Type of container
Fair testing:
To make it a fair test I will:
- Use the same size beaker each time so that each time the same amount of surface area is being heated.
- Test to make sure that the water is at the same temperature each time I start so that one experiment doesn’t have a head start.
- Use the same amount of water each time so that it doesn’t take longer to get to a certain temperature.
- Use a heat sensor attached to an easy sense pack to make my results more reliable as we can be more accurate with our recordings.
- Use the same sized burner for each one so that the same amount of fuel can escape at the same time.
Prediction
From the information I have gathered I predict that the Butan-1-ol will heat the water the fastest because it has the longest carbon chain. I know that more carbon molecules will give out more energy as they contain more carbon and hydrogen atoms which produce more carbon dioxide and water molecules so releasing more energy.
Equipment
- Heat proof mat
- Tripod
- Gauze
- Stop clock
- Heat sensor
- Easy-sense pack
-
100cm3 beaker
- Measuring cylinder
- Butan-1-ol burner
- Ethanol burner
- Propan-2-ol burner
- Safety specs
Method
-
Measure 50ml of water in the measuring cylinder and pour into the beaker. The temperature of the water should then be recorded (should be 14.5oC).
- Set up heat proof mat, gauze and tripod.
- Put beaker on top of the gauze with the fuel underneath.
- Place heat sensor attached to easy-sense in water without letting it touch the side or bottom of the beaker.
- Light wick in fuel and at the same time start the stop clock.
-
Record time when the temperature reaches 25 oC, 30 oC and 40 oC.
- This procedure should be repeated 3 times for each fuel.
Safety
To be safe whilst carrying out this experiment you should always:
- Tie back long hair.
- Always wear Safety Specs.
- If ethanol, propan-2-ol or butan-1-ol get in your eyes wash out immediately with clean water and seek medical advice.
- If you accidentally swallow some ethanol, propan-2-ol, butan-1-ol immediately wash out mouth with clean water and have a drink of water and seek medical advice.
- If ethanol, propan-2-ol or butan-1-ol spills on your clothes instantly remove clothing and wash both infected areas on body and clothing and then seek medical advice.
- Clean up spillages immediately with disinfectant and a cloth, rinse cloth out thoroughly after use.
- Always put out the flame when it is unattended.
- Always cover wick when it is not alight so that the vapours cannot escape.
Conclusion
My results indicate that the Butan-1-ol would make the best fuel because it heated the water the fastest. This matches my prediction.
Therefore I can work out that the longer the carbon chain the stronger the heat given off by the fuel. Butan-1-ol took only 539 seconds to get to 40 oC whilst propan-2-ol took 728 seconds this is a total difference of 189 seconds. This means that propan-2-ol does not make as good fuel as butan-1-ol because it would take longer to produce the same amount of heat.
Butan-1-ol makes a better fuel because it can heat things up faster and produce energy quicker.
Evaluation
If I did the experiment again I would change many things that would help improve the accuracy of my results:
- I would use a copper can as it transfers heat quicker which would mean that the water would get heated from all sides which would make the experiment fairer.
- I would use a clamp stand to hold the heat sensor so that it could be kept at the same spot in the water. This would make the temperature reading consistent as I would be measuring the same place in the water and not for example hot spots nearer the bottom of the beaker.
- I would try and make the wick the same size for each experiment, and use the same amount of fuel in each burner, so that one burner could not absorb and use more fuel.
- I would try and make sure that the burner is the same distance away from the container each time so that it could not skew my results by one fuel being closer than another and therefore heating the water up faster.
Also from my results I have noticed an anomaly, the third timing for butan-1-ol on 40 oC is very low. This could have been caused in a number of ways:
-
Firstly the volume of water may not have been exactly 50ml, because of an incorrect reading of the measuring cylinder. When the scale is being read it could be at a slight angle so that the light is refracted through the glass, causing the reading to appear somewhere else on the scale.
- Secondly this was the last experiment so the tripod may have been very hot so this would have caused the beaker to start heating up as soon as it was placed on the tripod.
Another anomaly is that the ethanol line crosses over with the propan-2-ol. This suggests that the starting temperature of ethanol was not the same as the rest. This could have been caused by using a beaker that was already hot so that it would have raised the temperature of the water.
