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Alcohols are used as a source of fuel in many countries. For it to turn into fuel, alcohol must be burnt. Alcohol is also a good clean source of energy and heat. In this experiment I will be trying to find out the amount of energy produced when different alcohols are burned.
In this experiment, the type of alcohol will be tested is Ethanol. Ethanol is a colourless liquid and is sometimes referred simply as alcohol or spirits. Carbon chains with a hydroxide molecule at the end of the chain make up an alcohol. Ethanol is a straight-chain alcohol and its molecular formula is C2H5OH. Its empirical formula however is C2H6O
The heat of combustion of any substance is the amount of heat energy given out when 1 mole of that substance burns completely in air. Every covalent bond existing in the molecule has a ‘bond energy’. This bond energy is the amount of energy needed to break the bond or the amount of energy given out as a bond is formed.
Concentration of an alcohol is related to the number of moles per decimetre cubed of the substance. The more concentrated the substance the more the substance will burn thus more heat energy is given out.
Will increasing the concentration of ethanol affect the heat of combustion of the alcohol?
It is hypothesised that increasing the concentration of ethanol will increase the heat of combustion of the alcohol.
The concentration of ethanol (Molar)
* 0.5 Molar ethanol
* 1.0 Molar ethanol
* 1.5 Molar ethanol
* 2.0 Molar ethanol
* 2.5 Molar ethanol
* Heat combustion of the alcohol (ï¿½C)
What will be controlled
How it will be controlled
Method of taking the temperature of water
The thermometer will be placed in the middle of the conical flask and the tip of the thermometer will be touching the bottom of the flask.
The conditions of the surrounding area
The experiment will be carried out in standard lab conditions.
Avoid contamination and residue to the next experiment when using the thermometer
Distilled water will be used to thoroughly clean out the equipments before experiment. Equipments will not be reused for the next experiments.
Drawing up data tables
Molar of Ethanol
Getting apparatus ready
1. Set up the electronic scale and attach the metal clamp to the retort stand
2. Using the label stickers and permanent pen, label the beakers that contain the different molar concentration of ethanol accordingly – 0.5; 1.0; 1.5; 2.0; 2.5
3. Label the beaker containing water
4. Using the distilled water, thoroughly clean out the conical flasks and measuring cylinders
Carrying out experiment
1. During the experiment, record any smell or colour of alcohol and any observation in the Qualitative Data table
2. Fill the conical flask with 100mL of water.
3. Place the thermometer inside the conical flask and record the initial temperature of the water
4. Keep the thermometer inside the conical flask
5. Clamp the flask at a height approximately 2cm from where the spirit burner will be placed below
6. Fill the spirit burner with just enough 0.5 Molar of ethanol so that the wick is half soaked in alcohol
7. Weigh the spirit burner attached with the lid containing the alcohol and record the initial mass
8. Place the spirit burner under the conical flask and use the matched to light the wick
9. When the water temperature reaches approximately 40ï¿½C, blow out and extinguish the flame
10. Record the exact temperature reached when flames were extinguished
11. Using the tongs, move the spirit burner and lid to the electronic scale and weigh the final mass
12. Dispose the water and alcohol inside the spirit burner
13. Repeat steps 1 – 11, but change the type of ethanol in respect to independent variables 1.0 Molar, 1.5 Molar, 2.0 Molar and 2.5 Molar of ethanol
14. When repeating steps 1 – 11, make sure a new conical flask and water is used and also a new spirit burner is used
15. When all five experiments of the different molar concentration of ethanol is completed, repeat the experiment another two times for each molar concentration of ethanol in reference to the data table
1. Final temp – Initial temp = Temp change (ï¿½C)
2. Final mass – Initial mass = Mass used (g)