Kinetic Particle Theory and States of Matter

Vocabulary flashcards covering key terms and concepts from the lecture on kinetic particle theory, states of matter, their properties, changes of state and diffusion.

Matter

Anything that has mass and occupies space, existing as solid, liquid or gas under ordinary conditions.

State of Matter

A physical form in which matter can exist—solid, liquid or gas (plus plasma and Bose–Einstein condensate in special cases).

Solid

State of matter with fixed shape and fixed volume; particles are closely packed in an orderly arrangement and can only vibrate in place.

Liquid

State of matter with fixed volume but no fixed shape; particles are close yet disordered and move freely throughout the substance.

Gas

State of matter with no fixed shape or volume; particles are far apart, move rapidly in all directions and can be compressed.

Plasma

A high-energy, electrically charged state of matter similar to a gas but consisting of ions and free electrons.

Bose–Einstein Condensate

State of matter formed near absolute zero where particles occupy the same quantum state and behave as a single ‘super-atom’.

Kinetic Particle Theory

Model stating that all matter is made of tiny particles in constant random motion, explaining states, properties and changes of matter.

Kinetic Energy (of particles)

Energy of motion possessed by particles; increases from solids to liquids to gases.

Compressibility

Ability of a substance to be forced into a smaller volume; gases are compressible, liquids and solids are not under normal conditions.

Melting

Change of state from solid to liquid when particles gain enough energy to overcome attractive forces.

Melting Point

Temperature at which a solid becomes a liquid; e.g., ice melts at 0 °C.

Freezing

Change of state from liquid to solid as particles lose energy and settle into fixed positions.

Freezing Point

Temperature at which a liquid solidifies; identical to the substance’s melting point.

Boiling

Change of state from liquid to gas throughout the liquid at its boiling point, producing bubbles.

Boiling Point

Temperature at which a liquid’s vapor pressure equals atmospheric pressure and it boils; water boils at 100 °C.

Evaporation

Slow change of a liquid to a gas at temperatures below boiling point, occurring only at the surface.

Condensation

Change of state from gas to liquid when particles lose energy and move closer together.

Sublimation

Direct change of state from solid to gas without becoming liquid; e.g., dry ice → CO₂ gas.

Heating Curve

Graph showing temperature change of a substance as it absorbs heat through melting and boiling.

Cooling Curve

Graph showing temperature change of a substance as it loses heat through freezing and condensation.

Volatile Liquid

Liquid that evaporates readily at room temperature due to a low boiling point; e.g., petrol, perfume.

Diffusion

Movement of particles from a region of higher concentration to one of lower concentration until evenly distributed.

Relative Molecular Mass

Mass of one molecule compared with 1⁄12 of a carbon-12 atom; lower values mean lighter, faster-moving gas particles.

Rate of Diffusion

Speed at which particles spread; increases with higher temperature and decreases with higher molecular mass.

Evidence for Particle Motion

Observations such as ‘dancing’ dust in sunlight or spreading smells that confirm constant random movement of particles.

Arrangement in Solids

Particles packed closely in a fixed, orderly lattice with strong attractions.

Arrangement in Liquids

Particles close but disordered with weaker attractions, allowing them to flow.

Arrangement in Gases

Particles very far apart with negligible attractions, moving freely and rapidly.

Compressibility of Gases

Large spaces between gas particles allow volume to decrease significantly under applied pressure.

Volumetric Property of Liquids

Liquids retain a fixed volume because particles, though mobile, are still close together and not compressible.

Energy Change in State

Heat absorbed converts to particle kinetic energy during melting/boiling; heat released to surroundings during freezing/condensation.

Homogeneous Mixture

Uniform mixture resulting from complete diffusion of one substance into another, such as bromine diffusing into air.

Effect of Temperature on Diffusion

Higher temperature gives particles more kinetic energy, causing faster diffusion in gases and liquids.