Overview
This lecture covers the three states of matter, their particle structures, changes of state, heating/cooling curves, and diffusion, including how temperature, pressure, and molecular mass affect gases.
States of Matter
- Matter is anything with mass that occupies space.
- There are three states of matter: solid, liquid, and gas.
- Solids have a fixed shape and volume; particles are tightly packed.
- Liquids have a fixed volume but take the shape of their container; particles are less tightly packed than solids.
- Gases have neither a fixed shape nor volume; particles are far apart and move freely.
Particle Structure and Motion
- Solid particles are very close together in a regular, ordered arrangement and only vibrate in place.
- Liquid particles are slightly separated, arranged randomly, and can slide past each other.
- Gas particles are widely separated, highly disordered, and move rapidly in all directions.
Changes of State
- Melting: solid to liquid at the melting point as particles gain kinetic energy (e.g., ice to water at 0°C).
- Boiling: liquid to gas at the boiling point as particles gain more kinetic energy (e.g., water to vapor at 100°C).
- Evaporation: gradual change from liquid to gas at temperatures below boiling point.
- Condensing: gas to liquid as particles lose energy and come closer together.
- Freezing: liquid to solid at the freezing point as particles lose kinetic energy (e.g., water to ice at 0°C).
Heating and Cooling Curves
- Heating curves show temperature changes as a substance is heated; temperature stays constant during state changes.
- Cooling curves show temperature drops as a substance cools from gas to liquid to solid; temperature remains steady during state changes.
Gas Volume and Pressure
- Increasing temperature increases gas particle motion and volume.
- Increasing pressure reduces the volume of a gas by forcing particles closer together.
- Decreasing pressure allows gas particles to spread out, increasing volume.
Diffusion and Relative Molecular Mass
- Diffusion is the spreading of particles from high to low concentration due to random motion.
- Lighter gases (lower molecular mass) diffuse faster than heavier gases (higher molecular mass).
Key Terms & Definitions
- Matter — Anything with mass that takes up space.
- Solid — State of matter with fixed shape and volume, tightly packed particles.
- Liquid — State with fixed volume, takes container's shape, particles can slide past each other.
- Gas — State with no fixed shape or volume, particles move freely.
- Melting Point — Temperature at which a solid turns to liquid.
- Boiling Point — Temperature at which a liquid turns to gas.
- Diffusion — Movement of particles from high to low concentration.
- Relative Molecular Mass — The mass of a molecule compared to one-twelfth of the mass of a carbon-12 atom.
Action Items / Next Steps
- Revise the properties and changes of state for solids, liquids, and gases.
- Practice drawing and interpreting heating and cooling curves.
- Study the effects of temperature and pressure on gas volume.
- Review the definition and examples of diffusion.