Lab 15: Evaporation and Intermolecular Attractions
Lab 15: Evaporation and Intermolecular Attractions
Pre-Lab Table
Data Table
Questions #2-4 (Calculations and Results)
2. Explain the differences in the difference in temperature of these substances as they evaporated. Explain your results in terms of intermolecular forces.
The differences in temperature of the substances as they evaporated can be attributed to their absorption of heat. When a liquid evaporates to become a gas, it must absorb energy (often in the form of heat) in order to break its intermolecular bonds and become a gas. This means that the energy (heat) must be absorbed from somewhere, and our group deduced that this source must be its surroundings--specifically the area around the temperature probe. The temperature probe recorded negative temperature drops for the filter paper because the heat in its surroundings was being absorbed as the substance evaporated, which would have resulted in a drop in temperature. Thus, our group decided that more drastic drops in temperature must've been to more energy required to break the intermolecular bonds holding some of the substances together.
The differences in temperature of the substances as they evaporated can be attributed to their absorption of heat. When a liquid evaporates to become a gas, it must absorb energy (often in the form of heat) in order to break its intermolecular bonds and become a gas. This means that the energy (heat) must be absorbed from somewhere, and our group deduced that this source must be its surroundings--specifically the area around the temperature probe. The temperature probe recorded negative temperature drops for the filter paper because the heat in its surroundings was being absorbed as the substance evaporated, which would have resulted in a drop in temperature. Thus, our group decided that more drastic drops in temperature must've been to more energy required to break the intermolecular bonds holding some of the substances together.
3. Explain the difference in evaporation of any two compounds that have similar molar masses. Explain your results in terms of intermolecular forces.
Although ethanol and glycerin had remarkable close molar masses, their temperature change data differed significantly. We believe that this is due to the greater number of hydrogen bonds found amongst glycerin as opposed to ethanol; glycerin contains 3 OH components within it while ethanol only has one. This gives glycerin a stronger intermolecular force which would mean that it would require more energy to evaporate. Thus, the temperature changes between these two substances would vary significantly.
Although ethanol and glycerin had remarkable close molar masses, their temperature change data differed significantly. We believe that this is due to the greater number of hydrogen bonds found amongst glycerin as opposed to ethanol; glycerin contains 3 OH components within it while ethanol only has one. This gives glycerin a stronger intermolecular force which would mean that it would require more energy to evaporate. Thus, the temperature changes between these two substances would vary significantly.
4. Explain how the number of -OH groups in the substances tested affects the ability of the tested compounds to evaporate. Explain your results in terms of intermolecular forces.
The OH groups in the substances affected their ability to evaporate by acting as potential for hydrogen bonding, which is one of the strongest intermolecular bonds. Thus, as a compound gains OH groups it also forms a stronger and stronger intermolecular bonds with other molecules of the same composition. With these stronger bonds, however, comes the need for more energy to break these bonds. This means that it requires more energy to allow the substance to evaporate. This conclusion was supported by our data; glycerin, which had three groups of OH,rose in temperature while another substance with only one group (such as ethanol) fell drastically in temperature; each of these requires a different amount of energy to evaporate. It also explains how glycerin continued to drip even after the four minutes had passed while ethanol ended up being slightly damp and did not drip at all.
The OH groups in the substances affected their ability to evaporate by acting as potential for hydrogen bonding, which is one of the strongest intermolecular bonds. Thus, as a compound gains OH groups it also forms a stronger and stronger intermolecular bonds with other molecules of the same composition. With these stronger bonds, however, comes the need for more energy to break these bonds. This means that it requires more energy to allow the substance to evaporate. This conclusion was supported by our data; glycerin, which had three groups of OH,rose in temperature while another substance with only one group (such as ethanol) fell drastically in temperature; each of these requires a different amount of energy to evaporate. It also explains how glycerin continued to drip even after the four minutes had passed while ethanol ended up being slightly damp and did not drip at all.
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