Lab 15: Evaporation and Intermolecular Attractions

   In the Evaporation and Intermolecular Attractions Lab, we found the change in temperature of four different substances by evaporating the substances. We used a LabQuest device to record the temperature of each substance while it was evaporating for 240 seconds. First, we wrapped the LabQuest probe in filter paper. Then we soaked the probe in one of the four substances for thirty seconds. After that, we set the probe on the table to evaporate and collect data.






 Calculation Questions

2. Explain the differences in the difference in temperature (𝝙𝗧) of these substances as they evaporated. Explain your results in terms of intermolecular forces.
   Due to each substances' different intermolecular forces, they all had varying changes in temperatures. For example, Methanol had the greatest value in change. This was due to its relatively weak intermolecular force compared to those of the other four substances. Therefore, it evaporated and cooled down more than the others. On the opposite side of the spectrum, n-Butanol had the least change in temperature. This meant that it had the strongest intermolecular force out of the five substances which slowed its evaporation and cooling. Lastly, while most of the substances dropped in temperature, glycerin's temperature increased. This was due to its three hydrogen bonds which created such a strong intermolecular force that it absorbed energy from the atmosphere.

3. Explain the difference in evaporation of any two compounds that have similar molar masses. Explain your results in terms of intermolecular forces.
   Methanol and Ethanol had similar molar masses. The change of temperature in methanol was greater than in ethanol however. They both had the same intermolecular force of hydrogen bonds. This caused Methanol to evaporate faster than Ethanol was that it had a lower molar mass. This proves that when the other factors are constant, substances with higher molar masses will take longer to evaporate than substances with lower molar masses.

 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.
   -OH groups are hydrogen bonds, and hydrogen bonds are the strongest intermolecular forces. The more -OH groups there are in a certain substance, the stronger it is. Methanol had one -OH group but a very low mass, so evaporated the most. While Ethanol also only had one -OH group, it had a higher molar mass than Methanol, so it evaporated second most. Additionally, water had one -OH group, a low molar mass, so it was in the middle in terms of evaporation rate. n-Butanol had one -OH group, but it also had a very high molar mass which caused it to come in second place of evaporating the least. Lastly, glycerin had three -OH groups in addition to the highest molar mass of the five substances. Therefore, it evaporated the least.



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