Solids, Liquids and Gases: Units

Understanding States of Matter: Solids, Liquids and Gases

Solids have a fixed shape and volume because the particles are arranged in a regular, repeating pattern.
The particles are closely packed together and their positions are fixed.
The main energy transfers involving solids are conduction and radiation.

Liquids take the shape of their container and have a fixed volume, but their shape can change.
The particles are closely packed, but not as much as in solids and they are able to move past each other, allowing flow.
Heat energy is primarily transferred through liquids by convection.

Gases have no fixed shape or volume. They spread out to fill any space available.
The particles are relatively far apart and are in constant, random motion.
In gases, heat energy is transferred through convection and radiation.

The transfer of energy within solids, liquids, and gases will depend on the state of the matter.
In solids, energy is transferred primarily through conduction, which is the process where vibrating particles pass their energy to neighbouring particles.
The primary method of energy transfer in liquids and gases is convection where particles with a lot of heat energy move and take the place of particles with less heat energy.
In gases, energy can also be transferred through radiation.

Changes in state are physical processes that involve energy transfers.
When a substance is heated, its particles gain kinetic energy and move faster, leading to expansion.
As a solid melts into a liquid or a liquid boils into a gas, the substance absorbs energy. This energy is used to break the bonds between particles.
Conversely, when a gas condenses into a liquid or a liquid freezes into a solid, energy is released.
Even when a substance changes state, its total amount of energy remains constant, which is a reflection of the principle of conservation of energy.