H C C C H H C C C C H
H H H H H H H
Propane C3H8 Butane C4H10
H H H H H
H C C C C C H
H H H H H
Pentane C5H12
These above are the structures of the natural gas hydrocarbons, but alcohols also contain hydrogen and carbon but they have a –OH (a functional group) attached some where in their structure. So there structure would look like this:
H H H
H C OH H C C OH
H H H
Methanol CH3OH Ethanol C2H5OH
H H H H H H H
H C C C OH H C C C C OH
H H H H H H H
Propanol C3H7OH Butanol C4H9OH
H H H H H
H C C C C C OH
H H H H H
Pentanol C5H11OH
Preliminary work.
Before I start my real experiment I need to plan how I will carry out the experiment and which measurements would be suitable for the experiment, also which apparatus I have chosen to use.
So in order to do this I did a preliminary experiment and I decided to keep the temperature of the water at the start of the experiment 20ºC for each alcohol and to heat it until it reaches 100ºC. Also to keep the amount of the water 100ml for each alcohol so this way it will be a fair test.
The apparatus I can use are: alcohols (spirit burners), balance, measuring cylinder, goggles, stop watch, thermometer, retort stand & boss and clamp, boiling tubes, heat proof mat, conical flask, beakers, metal containers, tripod and last of all rulers.
For my preliminary work I have used a thermometer, conical flask, balance, alcohols (spirit burners), retort stand & boss and clamp, heat proof mat and stop watch.
Preliminary results
As I can see from my preliminary results is that the experiment doesn’t take a lot of time to do, nor are these results inappropriate they look reliable and suitable. So therefore I am going to keep everything the same as it was in this experiment, to do my final experiment.
Apparatus:
Alcohols (spirit burners): These r used to heat the water and the alcohols I will be using are: Ethanol, Butanol, Propanol, and Pentanol.
Balance: To weigh the alcohols before and after heating the water to see how much fuel has been used.
Stopwatch: To time how long it takes the water to boil.
Thermometer: To see when the water has reached 100ºC.
Retort stand & boss and clamp: To hold the conical flask above the flame of the spirit burner.
Heatproof mat: for safety and to place the alcohols on when heating the water.
Conical flask: To put 100ml of water in it 2 heat.
Splint or lighter: To light the wick of the spirit burner.
Diagram:
Method:
- Set up apparatus as shown.
- Get a spirit burner weigh it using a balance, record the results in the table.
- Fill the conical flask with 100ml of water and place a thermometer in it and place it into the grips of the clamp and tighten it so it is fastened securely and just above the wick of the spirit burner.
- Place the alcohol on a heat proof mat and place it under the conical flask.
- Light the wick of the spirit burner with a lighter or splint, and start the stopwatch at the same time.
- Wait until the water temperature has reached 100ºC stop the watch and cover the spirit burner wiv the glass lid so the flame goes out, and record the time.
- Wait about 5 minutes for the spirit burner to cool because glass expands when it has been heated. Then weigh it and record the result.
- Repeat this method for each alcohol and then repeat the whole experiment at least once more to make the results slightly more accurate.
Results
Safety
For this experiment there are not many safety rules but you must wear goggles through out the experiment to protect the eyes. Also to keep the spirit burners on the heatproof mat at all times, and last of all not too heat the water so high that the thermometer breaks.
Maintaining accuracy
I will do this by:
- Keeping the temperature of the water at the start of the experiment 20ºC.
- Keeping the amount of water 100ml.
- Always heating the water to 100ºC.
- Using the same size conical flak.
- Using the same apparatus.
Result 1
Result 2
Averages
This table below shows how many moles are in the amount of grams used.
A mole is a word, which represents a number. Like the word "dozen" represents the number 12, so "mole" represents the number 6 x 1023. This number is also called Avogadro's number.
Analysis
By looking at my results and my graphs, I have found that pentanol uses the least fuel to heat the water. So therefore it is the most efficient fuel to use. Also I realised a trend by looking at the results as an average, that the reactivity of the alcohols depended on there Carbon bonds, so if an alcohol had less carbon bonds it wouldn’t be very reactive so there fore it would use more fuel to heat the water. But if the alcohol had more carbon bonds then it would use the least fuel to heat the water because it is more reactive. This was shown in my experiment because ethanol which has 2 carbon bonds, but more fuel was used (4.57) where as the next one up used slightly less which was propanol (3.28) with 3 carbon bonds, then butanol (3.49) with four carbon bonds which used even less, and last of all pentanol (2.62) which had 5 carbon bonds so therefore used the least fuel. I have also noticed that the least amount of moles it has the less fuel it uses to heat the water, by looking at the table above about the moles. So therefore my experiment relates to my scientific understanding of hydrocarbons because pentanol has the most amount of carbon bonds and uses the least fuel to heat the water. But the reaction has occurred due to combustion, which is a reaction between substances that is usually accompanied by generation of heat and light in the form of flame, in my case this is the spirit burner. In this case the combustion is a mixture of hydrogen combustion and carbon monoxide combustion, it’s hydrogen combustion because of the spread by the branched chain reactions. It is carbon-monoxide combustion because of the fast interaction step between a hydroxyl radical, which gives it an –OH bond. Explosions and detonation reactions can also occur during combustion.
Explosions: occur in combustion in a result of acceleration of the reaction, whether it is caused by a rise in temperature or by an increase in the lengths of reaction chains. A thermal explosion will occur if the rate of heat released by the reaction exceeds the rate of heat lost in the area. In this case it is most likely to be a chain explosion because this occurs when the probability of the chain branching or bond equal the chain of termination. When a combustion reaction accelerates, so that the flame front area advances at a high velocity, compression from the shock wave causes an increase in temperature that the result in self-ignition of the fuel.
So by looking at the above it proves that my prediction was correct. Because the above information and the hydrocarbons part all support my prediction, and my results agree with my prediction and so does my background information so therefore it must be correct.
Evaluation
I think that the method that I used to complete my experiment was successful because I ended up with quite accurate results, which matched with my prediction. Although I don’t think that my accuracy was of the best because I have one anomalous result, by looking at the averages line graph. This could be because of quite a few reasons but the main ones being:
- When reading the weight on the balance I might have miss read it.
- I might have missed read the temperature on the thermometer so therefore taken the fuel away to quickly or even later.
- The temperature of the water at the beginning may have varied.
- A different person may have read the readings on the thermometer so there fore the eye level was different and you would get a different reading.
So in order to make this experiment more reliable I could be more aware of the factors that affect my end result and try to keep the experiment as accurate as possible. I can do this by :
- Making sure the same person reads the reading of the thermometer.
- Making sure the temperature of the water is the same at the start.
- Reading the weight accurately.
Also I could improve the reliability by repeating the experiment if I find anymore anomalous results.
The evidence that I had gained in my prediction and my analysis can help to be sure that the result obtained was an anomalous result because it is supposed to be a straight-line graph, because that’s how each alcohol reacts. Pentanol, being the most reactive, and, ethanol being the least reactive.
Using different containers to put the water in can extend this experiment. You could use a tin can, boiling tubes, beaker of different sizes and many other containers that can be heated. My experiment could be changed to see how much fuel is used to heat up water in different containers. So therefore I could compare two containers with each other.
Overall I think my experiment was done well and I achieved fairly accurate results.
