Intermolecular Forces
Chapter Name : States Of Matter |
Sub Topic Code : 102_11_05_02_02 |
Topic Name : Intermolecular Forces |
|
Sub Topic Name : Dispersion Forces And London Forces |
|
Introduction
Intermolecular forces are the forces of attraction and repulsion between interacting particles (atoms and molecules). Attractive intermolecular forces are known as Van der Waals forces. Van der Waals forces vary considerably in magnitude and include dispersion forces or London forces, dipole-dipole forces, and dipole-induced dipole forces. • Force of attraction between two temporary dipoles is known as London force. • Another name for this force is dispersion force.
Pre-Requisites:
molecule, dipole, ion, halogen group
Activity:
Solids have strong inter-molecular forces, liquids have weak inter-molecular forces, and Therefore it is difficult for solids to flow.
Real Life Question:
Why is chlorine a gas, bromine a liquid and iodine a solid at STP?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| London dispersion forces | Forces of attraction between molecules caused by the temporary dipole moment of the molecules spaced very close together. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| Halogen lamp | Halogen lamps are used. |
Real life uses :
Halogen lamps, use iodine or bromine
Places to visit :
Garage,
Practical examples around us
| Examples | Explainations |
|---|---|
| Bromine occurs as a liquid at stp | London dispersion forces are greater in bromine as compared to fluorine or chlorine which is why it occurs as a liquid at STP. |
What you learn in Theory:
Forces of attraction between molecules that occur instantaneously between two temporary dipoles are called London dispersion force. It is commonly seen between molecules of halogen group.
What you learn in Practice:
Substances are solid, liquid or gaseous mainly due to different intermolecular forces between their molecules.