The Penny Lab
For this lab, you will complete the "Penny Lab Report" by using the "Penny Lab." Click on both of the buttons below, so you have the materials you need. Follow the instructions in the the "Penny Lab Report."
Intermolecular Forces
Intermolecular forces (IMFs) are the interactions between molecules. Intermolecular forces are weaker than either ionic or covalent bonds. The two weakest attractions between molecules are called van der Waals forces which consists of dipole interactions and dispersion forces. A dipole is when a molecules has two poles (positive and negative). Another type of intermolecular force is the hydrogen bond. Watch the following video from 1:04 to end.
There are four intermolecular forces to be aware of:
- Dipole-Dipole Force: An attraction between opposite charges in polar molecules. The slightly polar molecule is weakly attracted to the slightly positive region of another polar molecule.
- Ion-Dipole Force: A force of attraction between an ion and a polar molecule. For example, NaCl dissolves in water because of these forces.
- London Dispersion Forces: An electrostatic force between molecules as the result of the random, fleeting creation of dipoles.
- Hydrogen Bonds: A strong type of dipole-dipole attraction which occurs with the following: H-O, H-N and H-F. Hydrogen bonds explains expansion when water freezes and hydrogen bonds explain surface tension.
Bulk Properties
It is important to understand intermolecular forces because they affect the properties of different types of matter. For example,
ammonia (NH3) has a higher melting point than PF3 despite the fact that melting point increases as you move down a group of elements in the periodic table. Ammonia has a higher melting point because of the hydrogen bonds between nitrogen and hydrogen. Additionally, think back to when you learned about solids, liquids and gases.
ammonia (NH3) has a higher melting point than PF3 despite the fact that melting point increases as you move down a group of elements in the periodic table. Ammonia has a higher melting point because of the hydrogen bonds between nitrogen and hydrogen. Additionally, think back to when you learned about solids, liquids and gases.
- Solids have the highest intermolecular forces meaning they have a stronger glue holding them together which is why they stay the same shape. Think of the intermolecular forces in solids as gorilla super glue. It will hold two items together very well.
- Liquids are the middle man. They have slightly weaker intermolecular forces than solids which is why they are able to take the shape of the container and move around more. Think of the intermolecular forces in liquids as stick glue. It will kind of hold two things together.
- Gases have the weakest intermolecular forces. Most websites say the intermolecular forces are negligible (not there/not important), but keep in mind gases do have intermolecular forces, but they are very, very weak. It would be like not using glue at all to hold two things together which is why gases fly everywhere.
https://youtu.be/-QqTwJzi7Wo