Lab 15: Evaporation and Intermolecular Attractions

Lab 15: Evaporation and Intermolecular Attractions 

Purpose:

In this lab, we had five different substances that we measured the difference in temperature before anf after letting the liquid evaporate for four minutes. The purpose of this lab was to figure out the strongest intermolecular bond out of the five substances.

Pre Lab Table:


Lab Data:


Questions: 

2. The difference that Methanol had was -15 °C, Ethanol at -9.3 °C, n-Butanol with -3 °C, Glycerin at 3.7 °C and lastly Water at -3.4 °C. Between all five of the substances, the one with the biggest difference was Methanol with -15 °C which also shows has the weakest bond. While Glycerin with 3.7 °C has the strongest bond. The differences in the initial temperature and final temperature helps us understand the strength of the bond. This is because where there is a higher difference, there is a weaker bond and with a smaller difference there is a stronger bond. The differences in temperature for each of the substances were that they evaporate at different rates based off of the amount of hydrogen bonds and the atomic mass of each. The strength of the intermolecular forces were all the same for each of the substances and it determines how fast a substance evaporates. This meaning we determined the differences in temperature based off of the hydrogen bonds and the atomic mass.

3. When comparing both water and Methanol, they had different changes in temperature, but have similar molar masses. Water has a molar mass of about 18.02 and Methanol of about 32.04. The change in water was -3.4 °C while methanol was -15 °C the difference is about 11.6 °C. Water has two hydrogen bond while methanol has one. The strongest intermolecular group are hydrogen bonds meaning it is harder to evaporate explaining why the temperature was lower.

4. The number of -OH groups in the substances that we tested affected the ability to test the compounds to evaporate in the way that -OH groups have hydrogen bonds so they increase the strength of the intermolecular forces. The more -OH groups means it would take a longer amount of time to evaporate since there is a stronger force. In glycerin you could see when drawing the lewis dot structure that there were more -OH groups and it showed in the results that it took longer to evaporate. We measured the strength of the intermolecular forces in this lab and we saw the differences in the different liquids with help from the lewis dot structures.







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