* States of Matter: The state of matter (solid, liquid, gas) is determined by how tightly packed the particles are and how they move.
* Particle Movement: Particles in a substance are constantly in motion, but the *type* of motion changes with the state of matter.
* Solids: Particles are tightly packed and vibrate in fixed positions. They have very limited movement.
* Liquids: Particles are close together but can move around each other, allowing liquids to flow. They have more freedom of movement than solids.
* Gases: Particles are far apart and move rapidly and randomly in all directions. They have the greatest freedom of movement.
Changes of State and Particle Movement:
* Melting: When a solid melts into a liquid, the particles gain enough energy to overcome the forces holding them in fixed positions. They begin to move more freely, leading to a change in state.
* Freezing: When a liquid freezes into a solid, the particles lose energy and slow down. This allows the forces of attraction to hold them in fixed positions, resulting in a solid.
* Boiling/Evaporation: When a liquid boils or evaporates into a gas, the particles gain even more energy. They move so fast and with so much force that they overcome the forces holding them together in the liquid state, becoming a gas.
* Condensation: When a gas condenses into a liquid, the particles lose energy and slow down. This allows the forces of attraction to draw them closer together, forming a liquid.
* Sublimation: When a solid directly changes into a gas, the particles gain enough energy to escape the solid state without going through the liquid phase.
* Deposition: When a gas directly changes into a solid, the particles lose enough energy to settle into a fixed position without going through the liquid phase.
Key Takeaway: The energy that particles have determines how they move. Changes of state are simply changes in the *amount* of energy the particles have, leading to changes in how they move and how closely they are packed together.
