Lesson 9: States of Matter & Gas Laws

States of Matter & Gas Laws Reference

States of Matter

• Solid: fixed shape and volume; particles vibrate in fixed positions.
• Liquid: fixed volume, variable shape; particles slide past each other.
• Gas: variable shape and volume; particles move rapidly and randomly.
• Plasma: ionized gas (very high temperature); found in stars and lightning.

Phase Changes

• Solid → Liquid: melting (absorbs energy)
• Liquid → Gas: evaporation/boiling (absorbs energy)
• Gas → Liquid: condensation (releases energy)
• Liquid → Solid: freezing (releases energy)
• Solid → Gas: sublimation (dry ice, CO₂)

Kinetic Molecular Theory

Gas molecules are in constant random motion. Temperature is a measure of average kinetic energy. KE_avg = (3/2)kT where k = Boltzmann's constant.

Gas Laws

• Boyle's Law: P₁V₁ = P₂V₂ (constant T and n)
• Charles's Law: V₁/T₁ = V₂/T₂ (constant P and n)
• Gay-Lussac's Law: P₁/T₁ = P₂/T₂ (constant V and n)
• Ideal Gas Law: PV = nRT, where R = 0.08206 L·atm/(mol·K)

Real vs Ideal Gases

Ideal gas law assumes no intermolecular forces and point-mass molecules. Real gases deviate at high pressure and low temperature. The van der Waals equation corrects for these effects.