Physical Properties and Intermolecular Forces

Objectives

Students will:

• predict the type of intermolecular attractive force that will form between two identical particles.

• explain the differences in melting or boiling points based on the types of intermolecular forces present between particles.

Why?

So why do we care about intermolecular attractive forces? Think about water molecules. When an ice cube melts or when water boils in a pan on the stove, the covalent bonds holding the hydrogen and oxygen atoms together in the molecule remain intact. However, the attractions between water molecules, the intermolecular attractions, are affected by melting and boiling. Intermolecular attractions influence a variety of physical properties of compounds including melting points, boiling points, and solubility (ability to dissolve). In the last activity, you investigated the types of intermolecular attractive forces that cause molecules to attract. In this activity, you will investigate how these intermolecular attractive forces determine the melting point, boiling point, and solubility of a substance.

This interactive let's you change the intermolecular attractions between particles at the same temperature. While you can't actually do this in real life, this simulation will help you explore how the strength of intermolecular attractions determine if a substance is a solid, liquid, or gas at a given temperature.

Use this interactive to answer questions 1-4

The boiling point of a substance is the temperature at which the substance changes states from liquid to gas. Boiling point is a physical property that is determined by intermolecular attractions. In the interactive below, there are two tiny drops of liquid, one polar and the other non-polar. Use the interactive to answer questions 5-8

The diagram below shows two types of molecules that contain carbon atoms. In each molecule, carbon atoms are gray, hydrogen atoms are white, and oxygen atoms are red.

Use the diagram below to answer questions 9-14.

You probably know that oil and water don't mix. Did you ever wonder why? The interactive below shows polar water molecules and nonpolar oil molecules in a container together. Use the key below to identify each type of molecule.

Use the button to "shake up" the oil and water mixture. Then watch to see what happens to the oil and water as you let the container "settle".

IMAFs play a huge role in something that we do multiple times every single day: washing our hands.

Watch the video below about surfactants, then answer questions 17-18.

Watch the video below about how soap interacts with the coronavirus. As you watch, consider what you learned about IMAFs in substances such as water, oil, and alcohol..

Answer questions 19-

Click on the link below to launch a simulation to show how salt and sugar dissolve in water. Note: This simulation won't run on an iPad or some tablets. If someone in your group can't open the simulation, please have someone in the group share their screen so all team members can see the simulation.

https://phet.colorado.edu/sims/cheerpj/sugar-and-salt-solutions/latest/sugar-and-salt-solutions.html?simulation=sugar-and-salt-solutions