States of Matter

States of Matter

Basic Information

• Matter exists in three states: solid, liquid, and gas.

• These states can be changed by adding or removing heat - this process is known as a change of state.

• Solids have a fixed shape and volume, their particles are closely packed in regular arrangement.

• Liquids have a fixed volume but can change shape according to the container, particles in a liquid are close but can move past each other.

• Gases can change both shape and volume, particles in a gas move about freely and are far apart from each other.

Changing States

• Adding heat can cause a solid to become a liquid (melting) or a liquid to become a gas (evaporation).

• Removing heat can cause a gas to become a liquid (condensation) or a liquid to become a solid (freezing).

• The processes are reversible, meaning they can go in either direction. For instance, water can freeze into ice (liquid to solid) or melt back into water (solid to liquid).

• The temperature at which a substance melts or freezes is called its melting or freezing point.

• The temperature at which a substance evaporates or condenses is called its boiling or condensation point.

Keywords to Remember

• Solidification: The process of a liquid changing into a solid.

• Sublimation: The process of changing from a solid directly into a gas without first becoming a liquid.

• Deposition: The process where a gas changes directly into a solid without becoming a liquid first.

• Brownian motion: The random movement of particles in a fluid (a liquid or gas), as a result of their collisions with other particles.

• Diffusion: The intermingling of substances by the natural movement of their particles. An example would be a drop of food colouring spreading in water.

Remember these key points and continue practicing past paper questions to get familiar with the type of questions you may face. Always discuss any difficulties with your teacher.