Investigating Science 11–12 · Year 12

Temperature and gas volume: Charles’s law and an estimate of absolute zero

Module 6: Technologies

Practical, model not builtMedium risk

School laboratory, not for home

In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

This site has no interactive model of its own. Where a step or a material names a Concept Studio model, simulation or tool, it has not been built; an external simulation a step names (for example PhET) is not part of this site.

The idea

At constant pressure a gas’s volume is proportional to its absolute temperature, so extrapolating measured volumes to zero estimates absolute zero, and the equipment limits how good that estimate is.

Safety card

Medium riskA teacher supervises

Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

Hazards

scalds from hot water
glass syringe breakage

Controls

fill baths from a kettle with care and keep them below 80 °C
clamp the syringe; never force a stuck plunger

Note

Heat or hot water is used: follow the NSW Department of Education Chemical Safety in Schools (CSIS) package, Section 1, and record a RiskAssess risk assessment before the lesson.

What you need

a 100 mL glass gas syringe with a sealed tip, lightly lubricated so the plunger moves freely, clamped horizontally
a large water bath, ice, a kettle, thermometer or temperature probe, stirrer

How to do it

Set 50.0 mL of dry air in the syringe at room temperature and record the temperature.
Immerse the syringe barrel in the bath and change the temperature in steps of about 10 °C from 5 °C to 75 °C.
At each step stir, wait 3 minutes, tap the plunger gently and read the volume.
Plot volume against temperature in °C and extrapolate the line to zero volume.
Repeat the series, then evaluate the syringe, thermometer and method for random and systematic error.

What you should see

For an ideal gas, 50.0 mL at 20.0 °C becomes 46.6 mL at 0 °C and 58.5 mL at 70.0 °C, a straight line that reaches zero volume at −273 °C. Plunger friction makes readings lag and any water vapour in the air adds volume at the higher temperatures, so the learner’s intercept is an estimate whose error they explain; the gradient check is that equal temperature steps give equal volume steps.

What changes

What you change: temperature of the gas
What you measure: volume of the gas
What you keep the same: same amount of air (sealed)
pressure at atmospheric (free plunger)
wait time before each reading

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

Gas volume doubles when the Celsius temperature doubles.
Particles themselves get bigger when heated.
Absolute zero has been reached in this experiment.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Investigating Science Stage 6 Syllabus (2017), NESA; currentINS12-13 INS11/12-1 INS11/12-2 INS11/12-4
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

All Concept Studio activities