Chemistry Laboratory Report --- Evaporation: Intermolecular Attractions
Chemistry HL
Chemistry Laboratory Report
Evaporation: Intermolecular Attractions
- Data Collected
Table 1: Data collected by the class on different liquids
- Experiments
Chemical: Cyclohexane
Appearance: Clear colorless liquid
Molecular formula: C6H12
Structural formula: CH3CH2CH2CH2CH3
Measure division: 30 seconds
Time used: 5 minutes (300 seconds)
Table 2: Temperature of Cyclohexane at different time
Graph 1: Change in temperature of cyclohexane with time
- The scale of x-axis is used because timing starts at 0 seconds, and thus the whole record from time 0 to the end is all needed
- The scale of the y-axis is used because the lowest temperature recorded is 10 and the highest value is 27, so the scale below 10 is ...
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- Experiments
Chemical: Cyclohexane
Appearance: Clear colorless liquid
Molecular formula: C6H12
Structural formula: CH3CH2CH2CH2CH3
Measure division: 30 seconds
Time used: 5 minutes (300 seconds)
Table 2: Temperature of Cyclohexane at different time
Graph 1: Change in temperature of cyclohexane with time
- The scale of x-axis is used because timing starts at 0 seconds, and thus the whole record from time 0 to the end is all needed
- The scale of the y-axis is used because the lowest temperature recorded is 10 and the highest value is 27, so the scale below 10 is not needed.
Chemical: Butanol
Appearance: Clear, colorless liquid
Molecular formula: C2H6O
Structural Formula: CH3CH2OH
Measure division: 30 seconds
Time used: 7 minutes (300 seconds)
Table 3: Temperature of Butanol at different time
Graph 2: Change of temperature of butanol with time
- The scale of x-axis is used because timing starts at 0 seconds, and thus the whole record from time 0 to the end is all needed
- The scale of the y-axis is used because the lowest temperature recorded is 24.2 and the highest value is 26.2, so the scale below 24.2 is not needed.
- Explanation
- From Table 1, we can see that non-polar liquids tend to have a greater temperature difference, indicating that it cool down faster, than polar chemicals. This can be explained by the intermolecular forces of the molecules. Non-polar molecules have weaker intermolecular forces, with only van der Waals’ attraction, while polar molecules have both van der Waals’ forces and dipole-dipole attraction. Thus, less heat energy is required for the non-polar molecules to break the intermolecular forces, and attain enough energy to evaporate from the liquid. From the table, ethyl ether has the weakest intermolecular attraction while triethanolamine has the strongest.
- In the first experiment with cyclohexane, the temperature decreases a lot mainly because of the evaporation of cyclohexane that took place. The reading of the thermometer will decrease because evaporation is a process in which the molecules on the surface of the solution breaks the intermolecular forces and becomes vapor. This will mean that energy will be taken from other molecules, and thus the average kinetic energy will be reduced, which will cause a drop in temperature. Cyclohexane is non-polar, so the intermolecular forces will be weaker, as it only have van der Waals’ forces, and thus it is easier to break the bonds for evaporation, and thus the temperature change is larger.
- The second experiment is a test with butanol. The decrease in temperature is only a little, because the chemical is polar and thus the intermolecular forces are stronger than non-polar, making it harder to evaporate, and that is why the temperature decrease for evaporation is slight.
- Evaluation
- The data attained by the experiments may not be accurate, since the contact between the thermometer may not be full, and thus the decrease in temperature is not properly recorded
- Some of the temperature of the chemicals may not b recorded as I is out of range of the thermometer, which in turns result in inaccurate data.
Reference:
www.wikipedia.com