IB CHEMISTRY

1.5.1

Ideal Gas Model

The Ideal Gas Law works perfectly for "Ideal Gases". But what is an Ideal Gas?

Piston

Ideal Gas Simulator

PRESSURE60 kPa
300 K

Heats particles → Faster collisions

50 Units

Moves piston → Changes space

The Two Key Assumptions

  • 🤏
    1. Negligible Volume

    The particles themselves take up zero space compared to the empty space between them.

  • 🧊
    2. No Intermolecular Forces

    The particles do not attract or repel each other. They just bounce off (Elastic Collisions).

When does this fail?

Real gases occupy space and have attractions.

  • High Pressure: Particles are squashed together → Volume becomes significant.
  • Low Temperature: Particles move slowly → Attraction becomes significant (leading to condensation).

Student Practice Set

1.
Under which conditions does a Real Gas behave most like an Ideal Gas?