Overview
Brief introduction to kinetic molecular theory (KMT), phases of matter, phase changes, temperature vs heat, and plasma and non-Newtonian fluids.
Kinetic Molecular Theory Basics
- All matter is made of atoms/particles that are always in motion.
- Particles possess kinetic energy; motion exists even in solids.
- In solids, particles vibrate in fixed positions; motion is not obvious.
- Moving from solid to liquid to gas, particles gain energy and move faster.
- Particle speed and kinetic energy determine the phase of matter.
States of Matter: Particle Behavior and Properties
- Solid: particles closely packed, high density, fixed positions, vibrate only.
- Liquid: fixed volume, takes shape of container, particles move past each other.
- Gas: expands to fill available volume, particles move fast and collide often.
- Gas pressure is higher due to frequent collisions with walls and each other.
- Gases are compressible; solids are not compressible.
Temperature, Heat, and Kinetic Energy
- Temperature measures the average kinetic energy of particles in a substance.
- Higher temperature means faster particle motion and higher kinetic energy.
- Heat and temperature are not the same; adding heat may not change temperature.
- Phase changes occur by adding or removing heat/energy.
Phase Changes and Names
- Know the correct term when asked for “phase change” versus “phase.”
- Solid to liquid: melting (example: ice to liquid water).
- Liquid to solid: freezing.
- Liquid to gas: boiling or evaporation.
- Gas to liquid: condensation; seen as droplets forming on kettle sides.
- Solid to gas (directly): sublimation; no liquid phase in between.
- Gas to solid: deposition.
Summary Table: States and Phase Changes
| From State | To State | Process Name | Key Notes |
|---|
| Solid | Liquid | Melting | Add heat; particles gain energy and move more freely. |
| Liquid | Solid | Freezing | Remove heat; particles arrange into fixed positions. |
| Liquid | Gas | Boiling/Evaporation | Add heat; gas occupies available volume. |
| Gas | Liquid | Condensation | Remove heat; droplets form on cooler surfaces. |
| Solid | Gas | Sublimation | Direct transition; no liquid phase. |
| Gas | Solid | Deposition | Direct transition; no liquid phase. |
Intermolecular Forces
- Intermolecular forces hold particles together in solids and liquids.
- In gases, intermolecular forces are very weak or almost non-existent.
Formula: Kinetic Energy
- Kinetic energy is related to speed; faster particles have higher energy.
- KE formula introduced: KE = 1/2 × mass × velocity squared.
Plasma and Non-Newtonian Fluids
- Plasma: ionized gas; electrons escape atoms, leaving free electrons and positive ions.
- Oobleck: non-Newtonian fluid; behaves solid under pressure and liquid when pressure is removed.
Exam Tips
- Learn three to four clear differences between solid, liquid, and gas.
- Be precise: “phase” means solid/liquid/gas; “phase change” requires process names.
- Understand that adding/removing heat drives phase changes; temperature links to average kinetic energy.
Key Terms & Definitions
- Kinetic Molecular Theory: model describing matter as particles in constant motion.
- Kinetic Energy: energy due to motion; depends on mass and velocity squared.
- Temperature: measure of average kinetic energy of particles.
- Heat: energy transfer that can change phase without changing temperature.
- Intermolecular Forces: attractions between particles affecting phase behavior.
- Sublimation: solid to gas directly; no liquid phase.
- Deposition: gas to solid directly; no liquid phase.
- Plasma: ionized gas with free electrons and positive ions.
- Non-Newtonian Fluid: fluid whose viscosity changes with applied stress.
Action Items / Next Steps
- Memorize phase change names and corresponding directions.
- Practice tabulating differences between states for exam preparation.
- Review KE formula and link to particle speed and temperature.
- Watch next lesson on the heating curve for temperature-heat-phase relationships.