Air takes up space, can be squashed and expands
Push the plunger of a sealed syringe full of air, then warm and cool a flask with a balloon on its neck.
Core concept
Air is matter: it takes up space, can be compressed, exerts pressure and expands when heated
Topic: Air and gases
We cannot see air, but it is matter: it has mass: How much matter something has, measured in grams or kilograms. It is the same everywhere. All key words and takes up space. Air is a gas, so its particle: A tiny piece that matter is made of, far too small to see. All key words are far apart and move fast. Because there is so much space between them, air can be squashed (compressed) into a smaller volume: How much space something takes up, measured in millilitres or cubic centimetres. All key words, 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
- Seal the syringe nozzle and push the plunger from 50 mL to 25 mL and then 10 mL, recording the pressure.
- Open the nozzle and push the plunger in again.
- 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.