GCSE Chemistry B (Combined) OCR

States of Matter

States of Matter

• Matter is anything that has mass and takes up space.
• Matter exists in four states: solid, liquid, gas, and plasma.
• The state of matter is determined by the arrangement of particles and the energy of particles.

Solids

• In a solid, particles are tightly packed in a fixed, regular arrangement.
• The particles vibrate in fixed positions but do not move around.
• Solids have a definite volume and shape.

Liquids

• In a liquid, particles are close together but can move around each other in a random manner.
• Liquids take the shape of their container and have a definite volume.
• The particles in a liquid are constantly colliding and moving past each other.

Gases

• In a gas, particles are far apart and move in all directions in a random manner.
• Gases completely fill their container and can be easily compressed.
• The particles in a gas move fast and collide with each other and the walls of the container.

Plasma

• Plasma is an ionised gas, meaning it is a gas that has been energised until atomic electrons are dislodged.
• As a result, plasma contains a mixture of free-moving ions, electrons, positive ions, and neutral particles.
• Plasma is only found in certain conditions such as in large concentrations of energy (like the sun) or in fluorescent lights.

Changing States of Matter

• Melting is the transition from solid to liquid, and occurs when the temperature reaches the melting point of the substance.
• When liquid turns into gas, this is called evaporation.
• If a gas transforms into a liquid, this process is known as condensation.
• The transition from solid to gas (or vice versa) without passing through the liquid state is known as sublimation.
• The energy required to change a substance from a solid to a liquid (or from a liquid to a gas) is called latent heat.

Remember, in an exam situation, you should aim to use correct terminology and make sure to cover all the key points in your answers. Address the question directly, and do not include irrelevant information. Good luck with your revision!