Skip to content
Grade 8 Beginner About 15 min Version 1 Awaiting review Premium

Air takes up space, can be squashed and expands

We cannot see air, but it is matter: it has mass and takes up space. Air is a gas, so its particles are far apart and move fast. Because there is so much space between them, air can be squashed (compressed) into a smaller volume, and the particles then hit the walls more often, so its pressure rises. When air is heated, its particles move faster and spread out, so the air expands; when it is cooled, it contracts.

What you will learn

  • Show that air takes up space and can be compressed.
  • Describe how squashing air changes its pressure.
  • Show that air expands when heated and contracts when cooled.

Before you start

  • Know that gases are made of particles that move freely.

Materials

  • A 50 mL plastic syringe and a cap
  • A conical flask, a balloon, hot water and ice water

Equipment

  • Pressure sensor (optional) and a water bath

Procedure

  1. Seal the syringe nozzle and push the plunger from 50 mL to 25 mL and then 10 mL, recording the pressure.
  2. Open the nozzle and push the plunger in again.
  3. Stand the flask in hot water (80 °C), then in ice water (5 °C), and watch the balloon.

How this simulation is simplified

  • The syringe starts with 50 mL of air at 100 kPa, and its temperature stays the same.
  • The flask holds 500 mL of air at 25 °C; the balloon stretches without resisting.