Overview
This lecture covers physical properties and changes of matter, focusing on the three main states—solid, liquid, and gas—and how temperature and pressure affect them.
States of Matter
- Matter exists as solids, liquids, or gases, called phases or states of matter.
- Solids have definite shape and definite volume, are incompressible, and their particles vibrate in fixed positions.
- Liquids have indefinite shape, definite volume, are incompressible, and their particles move freely but remain close together.
- Gases have indefinite shape and volume, are compressible, and their particles are far apart and move rapidly.
Physical Properties of Matter
- Mass is the amount of matter in an object, measured in grams (g) or kilograms (kg).
- Volume is the space an object occupies, measured in liters (L) or milliliters (mL).
- Density is mass divided by volume (Density = mass/volume).
Changes in States of Matter
- Heating a solid increases particle vibration until melting point; at 0°C for ice, solid turns to liquid.
- Boiling point is the temperature (100°C for water) where liquid turns into gas throughout the entire liquid.
- Compressing a gas or lowering temperature can change a gas to a liquid.
Phase Changes
- Melting: Solid to liquid due to heat absorption (e.g., ice melting).
- Freezing: Liquid to solid when heat is lost (e.g., water freezing).
- Condensation: Gas to liquid as energy is lost (e.g., water vapor on glass).
- Evaporation: Liquid to gas below boiling point, usually at surface (e.g., pond water evaporating).
- Sublimation: Solid directly to gas, skipping liquid (e.g., dry ice).
- Deposition: Gas directly to solid, skipping liquid (e.g., frost forming).
Practice Questions (with Answers)
- Solid to gas directly: Sublimation.
- State with definite volume but not shape: Liquid.
- Solid characteristic NOT true: Ability to flow.
- Liquid to gas temperature: Boiling point.
Key Terms & Definitions
- Matter — Anything with mass and volume.
- Mass — Amount of matter in an object.
- Volume — Space occupied by an object.
- Density — Ratio of mass to volume (D = m/v).
- Incompressible — Cannot be compressed into a smaller volume.
- Boiling Point — Temperature at which liquid becomes gas.
- Melting Point — Temperature at which solid becomes liquid.
Action Items / Next Steps
- Review definitions and phase changes for exam preparation.
- Practice classifying examples of phase changes.
- Be familiar with calculating density and identifying states of matter.