Preliminary Work:
Apparatus: 250ml beakers, 250ml tap water, ceramic mat, retort stand, bosse, clamp, crucible, ceramic wool, ethanol, pipette, 10ml measuring cylinder, thermometer, splint, tongs.
Method: Firstly a retort stand was taken as well as a bosse and clamp. Then a 250ml beaker was taken and filled with 250ml of tap water. Then the bosse and clamp was fitted on to the retort stand and the beaker filled with water was then fitted on to the clamp so that the clamp held it. Then a thermometer was taken and placed in the water of the beaker. Then a crucible was taken and then 2cm² of ceramic wool was taken and placed in the crucible. Then a 10ml-measuring cylinder and dropping pipette was taken and different volumes of ethanol were dropped into the measuring cylinder. The contents of the measuring cylinder were then poured onto the ceramic wool within the crucible. The temperature on the thermometer was then read off and recorded. Then crucible was then placed under the beaker and set a flame by means of a lighted splint. The next step in the experiment was to wait for the flame to die out. When the flame had done so, the reading on the thermometer was read off and recorded and the difference in starting temperature and ending temperature was worked out. The water in the beaker was then replaced with another 250ml of tap water. This process was used for all volumes for ethanol. Once all the alcohols were tested, the same procedure was undertaken using different alcohols but with the same volume of 3ml. All visual observations were recorded as well as results and data from the change in temperature.
Results:
This table shows the results obtained from the preliminary experiment using the volume of alcohol as the variable.
Background Information:
Alcohols are a part of organic chemistry. All alcohols are known to react to different reactions in a similar or identical way. Alcohols as a group consist of carbon atoms (C atoms), hydrogen atoms (H atoms and hydroxide atoms (-OH atoms). Alcohols are chemically formed when alkenes undergo an addition reaction with water. This reaction is helped by the presence of heat, pressure and a catalyst. An example of this is ethene and water forming ethanol as shown in this structural diagram:
H H H H
C=C + H20 H C C OH
H H H H
Combustion of alcohols:
This table below displays different alcohols and their properties:
From this table of properties we can work out that the general formula for alcohols is CnH2n+1OH.
Hypothesis: Using the preliminary experiment and my background knowledge as a basis, I have come up with a hypothesis that suggests that the rise in temperature of water will increase as the volume of ethanol is increased. This is because an increase in ethanol volume means that there is more alcohol to combust. This would result in more heat energy given off and thus a higher rise in temperature of the water. An increased volume of ethanol also results in more molecules being broken by heat energy once again. This again heightens the rise in temperature, as more heat is required for the breakdown of more molecules. I also think that when more ethanol is used, the longer the flame will burn for. This again is because more combustion of the alcohol is required by heat energy and thus the requirement of a longer flame.
Predictions: My predictions in this experiment are mainly based on the relationship between volumes of alcohol and the difference in temperature of water. One prediction in this experiment is that the relationship between volume of ethanol burnt and temperature rise will be proportional, i.e. if I double the volume of ethanol used to burn, I will double the temperature rise of the water, if I triple the volume of ethanol burnt, I will triple the temperature rise of the water etc. My graph also suggests that the relationship between the volume and rise in temperature will be more or less proportional.
Method:
Chosen variable- volume
Chosen alcohol- ethanol
As volume of alcohol is the changing variable, the output variable will be temperature change of water. This shall be measured using a thermometer. The range of volumes that are going to be used are; 1ml, 2ml, 3ml, 4ml, 5ml. This range will give me enough data to produce a graph of a good quality.
Apparatus List:
200ml beaker- used to hold water and thermometer
200ml tap water-required to receive heat from flame to trigger temperature change
100ml-measuring cylinder- used to measure the 200ml of tap water accurately
Thermometer- needed to measure change in temperature in water
Ceramic Mat- used for safety reasons
Ceramic wool- needed to soak up alcohol and also used as to set alcohol as flame
Ethanol- alcohol used within experiment
Crucible- will hold the ceramic wool and alcohol
Retort Stand- required so that beaker will be above flame
Bosse- needed to hold clamp onto retort stand
Clamp- needed to hold beaker above flame
10ml-measuring cylinder- used to measure volume of alcohol accurately
Dropping pipette- used to extract alcohol from bottles and into measuring cylinder to acquire accurate measurements
Tongs- needed to adjust hot crucible
Splint- required to start reaction
Safety spectacles- safety precaution
Apron- safety precaution
Safety- In this experiment the main safety concerns are of the flame derived from the burning alcohol and of the warm water. Other concerns include, hot apparatus and spillages. To avoid these concerns, safety spectacles are to be worn to protect the eyes, aprons are to be worn to protect the body, tongs are to be used when handling hot apparatus and general care is to be taken when carrying out the experiment.
Fair Test- To ensure that this experiment is a fair test, the volume of alcohol is to be measured accurately using the correct apparatus. The alcohol is kept the same (ethanol). All other variables will be kept at a constant and this will ensure a fait test. I also intend on doing two replicates as the time for this experiment suggests.
Planned Method- Firstly, a retort stand is taken and placed next to a ceramic mat. Then a bosse and clamp are fitted onto the retort stand. A 200ml beaker is then taken and filled with 200ml of tap water using a 100ml-measuring cylinder to measure the amount of water accurately. Then the beaker filled with water is held using the clamp fitted on the retort stand. A thermometer is then taken and placed in the water within the beaker. The temperature of the water within the beaker is then recorded as the starting temperature. Once the beaker is firmly in place within the clamp, a crucible is taken and within it, is placed approximately 2cm² of ceramic wool. The crucible is then set aside. A 10ml-measuring cylinder, dropping pipette and a bottle containing ethanol is then taken. Using the dropping pipette, 1ml³ of ethanol is placed into the 10ml-measuring cylinder. The alcohol in the measuring cylinder is then poured on the ceramic wool within the crucible. Then, using a lighted splint, the ceramic wool and ethanol is lit. The crucible is then moved directly under the beaker using tongs. The change in temperature is observed until the flame from the burning alcohol dies out. The finishing temperature is then read off the thermometer and noted. The difference in the temperature is worked out. The crucible is then moved from beneath the crucible using tongs and the ceramic wool is disposed of using the tongs again. The water in the beaker is left to cool for a while the process is repeated using the remaining volumes. At each time the new starting temperature is recorded before the ceramic wool and ethanol is lit. When replicating, the water from the beaker is replaced with new tap water.
Diagrams:
Skill O- Obtaining Evidence:
Visual Observations:
- During the experiment, steam or water vapour could be seen escaping from the water surface from the beaker. This means there was a significant amount of heat loss occurring.
- For the higher volume of 5ml³, soot or carbon was present on the bottom of the beaker. This is from the flame of the burning alcohol.
Skill A- Analysis and Considering Evidence
Method Update- no changes were made from the method used in the original experiment.
Results- See Skill O (page 7)
Visual Presentation- see graphs
Conclusion- In conclusion, I have discovered that as the volume of ethanol increases, the rise in temperature also increases. This statement is gathered up from information given by the graphs and data tables shown previously. The graphs shows that there is proportion between the variables. This would mean that as the volume of ethanol increases, the rise in temperature increases too but in more or less equal intervals. From reviewing the results we can see that for each ml³ increases, the rise in temperature is approximately 10°C. For example the rise in temperature acquired for 1ml³ was 23.67°C and the rise in temperature obtained for 2ml³ was 34.67°C. This gives a difference of 11°C between them. This is essentially the case with all the results and thus proportionality. I have found that my hypothesis was supported as the rise in temperature did increase as the volume of ethanol increased. This is because an increase in the volume of ethanol means that there is more alcohol to combust. Full combustion of the alcohol would require excess oxygen and therefore this explains the importance of the flame. And so this would result in more heat energy given off and thus a higher rise in temperature of the water. An increased volume of ethanol also results in more hydrocarbon molecules being broken by heat energy once again. This again heightens the rise in temperature, as more heat is required for the breakdown of more molecules. However, incomplete combustion was found at higher volumes such as 5ml³. This would explain the build up of soot on apparatus. This is because incomplete combustion of the ethanol forms carbon monoxide and carbon. In this experiment the carbon from the incomplete combustion is the soot built up on the apparatus. This may have occurred because there was a lack in excess oxygen and so incomplete combustion of ethanol occurs. This in turn means that not all of the hydrocarbon molecules formed CO2 and H20. The general equation for the experiment would be the following:
C2H6 + 2O2 2CO2 + 2H2O
Skill E- Evaluating
Overall, I think my evidence is quite reliable and the procedures used were of a reasonable accuracy standard. My apparatus allowed me to work to an average standard of accuracy. I think the results would have been of a better standard if the beaker was set at a fixed point each time and if there was a cover over the beaker to prevent heat loss. Out of all my data there was only one anomalous result. This can be found in the graph for the actual experiment. The result is not exactly anomalous as it fitted the basic trend of an increase as the volume increases but the increase was not as proportional as the rest of the results. I think this anomaly occurred due to heat loss from the water within the beaker as I could see steam rising from the waters surface in significant amounts for this reading. I think the procedure that I used was very suitable for the variable I was testing. However if I was to obtain better readings I think I would have to go about this by setting a fixed distance between the flame and the beaker at all times. With the data and visual representation of the graph I can come to a firm conclusion that can be justified with the use of background knowledge. If I was to investigate further, I could time the length of the reaction and plot a graph of the relationship between the time taken for the flame to die out and the rise in temperature. This in turn would give me information about the rate of the reaction.
