How can meteorite density link to GCSE practical work?

Question

Accepted Answer

Measuring the density of irregular solids by water displacement is a standard GCSE physics practical, and meteorite replicas or rock samples give it a real purpose.

Many GCSE physics specifications include a practical on determining density, including irregular solids measured by displacement. Meteorites provide an engaging context.

Set-up. Provide a range of rock samples: basalt, granite, sandstone, haematite or magnetite ore, pumice, and if possible a meteorite replica of known density or a small genuine specimen sealed in plastic, measured with allowance for the casing. Students use a balance, measuring cylinder or displacement can, and thread.

Method. Students measure mass, then volume by displacement, and calculate density. They repeat measurements and calculate means. Encourage them to record uncertainty: the resolution of the measuring cylinder often dominates.

Analysis. Students compare results with reference values: iron meteorites about 7.8 grams per cubic centimetre, ordinary chondrites about 3.2 to 3.7, granite about 2.7. They discuss whether density alone could identify a meteorite. Iron ores also have high densities, so it cannot.

Evaluation. Discuss sources of error: trapped air bubbles, water absorbed by porous rock, reading the meniscus, and small volumes. Students suggest improvements, such as using a smaller-diameter measuring cylinder or a more precise balance.

Extension. Students calculate the expected density of a stony-iron with a given percentage of metal and silicate, or estimate the mass of an asteroid from its size and assumed density, linking to space physics.

Safety. Handle heavy samples carefully, wipe up spills to avoid slips, and dry samples thoroughly, especially iron, to prevent rust.

How can meteorite density link to GCSE practical work?

More about for teachers