Grade 8 Chemistry: Particles & Matter

Matter is composed of constantly moving particles with spaces between them, and its state and properties depend on particle arrangement, movement, and bonding.

Core Principles

All matter consists of tiny, moving particles.
Particle movement speed increases with temperature.
Spaces exist between particles.
Particles exert attractive forces on each other.
States of matter (solid, liquid, gas) differ in particle arrangement and movement.
Changes of state involve energy transfer.
Elements, compounds, and mixtures are classified by particle composition and bonding.
Physical changes alter appearance but not substance; chemical changes form new substances.

Key Terms

Particle Model: Concept that all matter is made of tiny, moving particles.
Solid: State of matter with fixed shape and volume; particles vibrate in place.
Liquid: State of matter with fixed volume but variable shape; particles slide past each other.
Gas: State of matter with variable shape and volume; particles move fast and far apart.
Melting: Phase transition from solid to liquid.
Freezing: Phase transition from liquid to solid.
Evaporation/Boiling: Phase transition from liquid to gas.
Condensation: Phase transition from gas to liquid.
Sublimation: Phase transition from solid directly to gas.
Deposition: Phase transition from gas directly to solid.
Element: Pure substance made of only one type of atom.
Compound: Substance formed from two or more different atoms chemically bonded in a fixed ratio.
Mixture: Combination of substances not chemically bonded, separable by physical means.
Homogeneous Mixture: A mixture that is uniform throughout (e.g., salt water).
Heterogeneous Mixture: A mixture that is not uniform throughout (e.g., salad).
Physical Change: Change affecting the form of a substance but not its chemical composition.
Chemical Change: Change that results in the formation of new chemical substances.

Timeline

Heating: Energy In: Melting (Solid → Liquid), Evaporation/Boiling (Liquid → Gas), Sublimation (Solid → Gas)
Cooling: Energy Out: Freezing (Liquid → Solid), Condensation (Gas → Liquid), Deposition (Gas → Solid)