Pilot Experiment
I carried out a pilot to see if the method I planned to carry out would work. I have then modified it so that my final results are more accurate than these have been. I have chosen to pilot three different fuels because I think that piloting all the solutions would be pointless, this way I make sure that the method I am using works, it also helps me decide exactly how I will carry out my experiment ensuring that I get the most accurate results possible. I chose to pilot Methanol, Butanol and Hexanol, I did this to give me rough guideline of what my results should be like.
Pilot Apparatus
- Calorimeter
- Boss
- Clamp and Stand
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100cm3 measuring cylinder
- Thermometer
- Heating mat
- Mini Beaker
- Rocksil Wool
- 3 Different Alcohols
- Ruler
- Top Pan Balance
Pilot Method
- Measure 100cm3 of water and put in calorimeter.
- Put calorimeter in boss and clap stand
- Weigh 1 gram of fuel in to mini beaker
- Make a wick out of the Rocksil wool
- Place under the calorimeter
- Take the temperature of the water
- Set the wick alight with a light splint
- When the alcohol has completed burning take the temperature of the water
- Record your results.
Pilot Results
Analysis Of Pilot
In my pilot I found that my results were very inaccurate because I had not controlled enough of my variables for my experiment to be fair. For my real experiment I am going to change my method so that it will be a fair test.
I will modify my experiment by:
- Placing silver tin foil over the top of the calorimeter and putting the thermometer through it.
- Putting a cardboard screen round my experiment to try and stop heat loss between the top of the flame from the mini beaker and the base of the calorimeter.
- I will measure the distance between the top of the wick and the bottom of the calorimeter; the distance is going to be 10cm.
- I will measure the length of the wick, which will be 3cm, 0.5cm taller than the mini beaker.
- I will measure the height of the mini beaker, the one I a going to use is 2.5cm tall.
My results show me that my method was not very accurate because the temperature rise for Butanol and Hexanol are only one degree away. I hope that my real results are more accurate than these, if they are not I will repeat the burning until it is a reliable result and class the other result as an anomalous result.
Key Variables
To make a fair test I must only change one variable at a time, the one I am investigating. I must keep all the other variables constant.
Dependant – The dependant variable is the thing that you are measuring, in this experiment I am going to measure the temperature rise when different alcohols are burnt.
Independent – The independent variable is the thing that you are going to investigate, in this experiment I am going to use different alcohol, which go down a series.
Controlled - To make a fair test I must only change one variable at a time, the one I am investigating. I must keep all the other variables the same.
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Same Apparatus – I must use the same apparatus for all my experiments because the apparatus may be a different shape or size. I will attempt to control this variable by making sure that I use the same size mini beaker and calorimeter and the same type of thermometer.
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Same Top Pan Balance – Each top pan balance weighs slightly differently, if I used a different balance for each alcohol there may be slightly more or slightly less of the alcohol, this may make my experiment inaccurate. I will control this variable by
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Same Room Temperature – I will not be able to control this variable because I do not have enough time in one lesson to all of the practical, including repeats. Although I do not think that room temperature difference of 5o will make that much difference to my results.
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Amount Of Water – I must use the same amount of water because more water will not increase in temperature as much as 100cm3, and less water will heat up more, this will make my result in accurate. I am going to control this variable by using a measuring cylinder to measure the water; this is accurate enough for this experiment.
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Size Of Wick – I will make sure that my wicks are always the same length because otherwise my results may be inaccurate because the bottom of the calorimeter and the top of the wick ma be closer which will cause greater heat loss than there already is. Therefore I will measure the wick to make sure it is the same length, it will be 0.5cm taller than the mini beaker therefore it is 3.0cm.
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Distance Between Calorimeter And Mini Beaker – I will keep the distance between the calorimeter and the top of the mini beaker to keep the amount of heat loss constant, I know that there will be a great deal of heat loss therefore I will keep the heat loss the same. I will do this by measuring the distance between the top of the mini beaker and the bottom of the calorimeter the same. The distance will be 10cm all the time.
Method
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Measure 100cm3 of water and put in calorimeter
- Put calorimeter in boss and clap stand
- Cut a small piece of foil, just big enough to cover the top of the calorimeter, to act as a lid
- Put the thermometer through the foil
- Weigh 1 gram of fuel in to mini beaker
- Make a wick out of the Rocksil wool, it should be 3 cm long and not to thick
- Dip the top of the wick in to the alcohol, this helps it light
- Place under the calorimeter
- Measure the distance between the top of the wick and the base of the calorimeter, it should be 10 cm
- Make a three sided cardboard screen to go round the gap between the mini beaker and the calorimeter
- Take the temperature of the water
- Set the wick alight with a light splint
- When the alcohol has completed burning take the temperature of the water
- Record your results in a table
- Before starting the experiment again wipe the bottom of the calorimeter to remove any soot.
- Repeat this method of all the alcohols, and the repeats.
Prediction
I predict that when I burn one of the alcohols it will make the temperature of the water increase. As I go down the homologous series the temperature will increase. This is because in a lower alcohol, such as Butanol or Hexanol there is a longer chain of carbon bond, which need a greater heat to be broken, carbon carbon bonds need more energy to break the bonds in the chain. The longer the chain the higher the temperature needed to break bonds. Methanol and Ethanol have a short carbon chain and therefore need less energy to break bonds. To break any bond a certain amount of energy is needed, the amount of energy needed to break bonds in the alcohols increases as you go down the alcohols.
Diagrams
Safety
- Wear safety goggles when burning alcohol
- Tie lose hair back
- Take off all lose clothing
- Keep the room you are carrying out the experiment in well ventilated
Results
In my results table I have marked all anomalous results with purple so that they stand out. I had an anomalous result in each different alcohol, when I found I had an anomalous I repeated the experiment so that all my results were with in 3oC of each other. I have not included any of my anomalous results in my average. See next page for results table.
Analysis
My results show me that as you go down the alcohol series the temperature the water increases to increases by around 6oC each time. I have drawn two graphs, I will number them 1 and 2, number 1 is for the average temperature, 2 is for the energy given out. Graph number 1 shows me that
