HS Chemistry - Intermolecular Forces

States of Matter

Overview of The Page

This page will cover:

What are the different states of matter? What are the differences between them?
How are intermolecular forces different in each of the states of matter?

There are three main states of matter: gas, liquid, and solid. They are identified and distinguished primarily by the strength of the intermolecular forces between the molecules. When the forces of attraction between molecules are stronger, the molecules move closer together.

In a gas, the molecules expand to occupy the shape and volume of the character. They are not connected to one another. For this reason, they can be compressed to a smaller size, as there is empty space between the molecules. The intermolecular forces of attraction between the molecules are weak.

Molecules in a gas are far apart

In a gas, the molecules are far apart - they expand to fill the volume and shape of their container. They are not connected to each other, and randomly move around at varying speeds in vary directions, shown by arrows and their lengths here. There is a lot of space between the molecules, so they can be compressed to smaller volumes. The intermolecular forces of attraction are weakest in the gas state.

In a liquid, the molecules take the shape of their container, but they do not expand to fill its volume. Although the molecules can move around and over each other, they remain connected to one another. For this reason, liquids can't be compressed anywhere near as much as gases, as there is little empty space between the molecules. The intermolecular forces of attraction between the molecules are stronger than in gases, but weaker than they are in solids.

Molecules in a liquid are closer together

In a liquid, the molecules are close together, but not as close as they are in solids - although they do not expand to fill their container, they take its shape. While they remain connected to each other, they still move and slide around, not represented here. There isn't much space between the molecules, so they can't be compressed as much as gases. The intermolecular forces of attraction are stronger in liquids than they are in gases, but weaker than they are in solids.

In a solid, the molecules do not expand to fill the volume, nor do they take the shape of their container - they remain in the shape they are currently in. They are connected to each other, and cannot move or slide over one another - they can only vibrate in their positions. For this reason, solids can't be compressed anywhere near as much as gases - there is far less empty space between the molecules. The intermolecular forces of attraction between the molecules are stronger in solids than they are in liquids.

Molecules in a solid are very close together

Solids and liquids can barely be compressed, because the molecules are already very close together, and are touching one another. For this reason, solids and liquids are called the condensed phases.

Different states of matter have different energies of attraction between particles, and different kinetic energies of the particles.

In a gas, the kinetic energies of the particles are very high, while the energies of attraction are very low.

In a liquid, the kinetic energies of the particles are close to the energies of attraction.

In a solid, the kinetic energies of the particles are low, while the energies of attraction are high.

The kinetic energies of the particles also affect the rate of diffusion. If the particles can move fast, then they can diffuse quickly. For this reason, diffusion happens much faster in gases than in liquids, and much faster in liquids than in solids.