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Physics notebook Cambridge IGCSE 0625

Gas pressure and temperature · 3 parts · syllabus 2.1.2, 2.1.3, 2.2.1

Why can a sealed can burst when it gets hot?

Trap some air in a syringe joined to a pressure gauge and squeeze it to smaller and smaller volumes, with a magnifier showing a model of its particles. Then lock the plunger, cool the air with ice and warm it on a hotplate, and extend the graph to find where the pressure would reach zero.

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A plain aerosol spray can lying on the dashboard of a parked car, in strong sunshine under the windscreen. (enlarge)

Follow the idea

  1. Squeezing a gas

    Gas pressure from particles hitting the walls, as a force per unit area; squeezing a gas at a steady temperature, and pV = constant with its graphs

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  2. Heating a gas at a fixed volume

    Heating a gas at a fixed volume, in particle terms; the kelvin scale and T = θ + 273

    Not started

  3. Thermal expansion

    Thermal expansion of solids, liquids and gases, why gases expand most, and where expansion is useful or a problem

    Not started
A glass gas syringe standing nozzle down in a beaker of water on a hotplate, held by a clamp, with a collar on the stand holding the plunger still. A thin tube runs from the nozzle to a dial pressure gauge, and a thermometer dips into the water.

The experiment · Squeeze trapped air · then lock it, cool it and warm it

Run it yourself, or project it for the class

Use the apparatus step by step and look closely at what happens. The whole experiment fits one screen, so it works on a projector too.

Open the experiment