4.Main Content
experiments
Examples of solids, liquids and gases
Demonstration
An exhibition of a wide variety of natural and synthetic materials for students to look at and handle - if possible over several weeks. It makes an ideal start to a course in Physics at whatever age that takes place.
Apparatus and materials
Whatever can be made available. Suggestions are:
• Metal blocks such as iron, aluminium, brass, lead
• Examples of soft wood and hard wood e.g. Formica and plywood
• Paraffin wax
• Foamed polystyrene, Perspex, or other polymers
• Glass of any type
• Building stone such as slate and marble
• Rubber, latex foam block, steel spring, bare copper wire
• Alum, sodium thiosulfate (hypo)
• Common salt, washing soda, silk, cotton, wool, curry powder, soap, vinegar, olive oil, gelatine, wheat, flour, greaseproof paper, paper
• Copper sulfate, calcite, cast bismuth
• Lead shot, Bakelite, granite, basalt, limestone, sandstone, schist, mica, flowers of sulfur, glass camphor, Milton (chlorine bleach), pitch, chalk, concrete, brick, ceramic, plaster of Paris, tungsten carbide tipped drill
• Glass bottles containing air and one from which some air has been evacuated (labelled AIR and VACUUM).
• Balloon full of air, one with hydrogen (or, if that is not available, natural gas), one with carbon dioxide.
Offering hand lenses might be useful.
Technical notes
Science apparatus manufacturers including Philip Harris and Griffin Education sell elastic materials investigation kits and solid materials kits.
The bigger the size of samples, the more convenient is it for handling and viewing. However, if the samples can be of a similar size, relative densities will be more obvious. A suitable size would be 3 cm x 4 cm x 5 cm. Light plastic containers of the same volume (and shape) would be useful for holding liquids.
As far as possible, the substances exhibited should be common ones, of a domestic nature rather than special chemicals outside the students' experience.
The sense of smell is important which is why the list includes some items with strong smells,
Balloons should be filled immediately before display. Hydrogen, in particular, will diffuse quite quickly through the walls of the balloon. It is helpful to stretch a balloon before trying to inflate it. This softens the walls.
Safety
Hands must be washed after handling lead. The general warning not to taste anything and to 'smell with care' should be repeated.
Read our standard health & safety guidance
Procedure
Ask students to examine all the exhibits - without spending too long with each one. It will give their examination some focus if they are required to compile lists, say, hard or soft, or solid, liquid or gas.
If students do not seem to be thinking about why the materials differ ask a few leading questions such as "Why might a solid iron be different from aluminium?" Or you could develop a game of 20 questions to identify a material.
Teaching notes
1 The aim of the exhibition is that students closely examine different materials and begin to wonder why there are these differences. They may also
• get a feeling for density.
• wonder why materials have different properties.
2 Draw students' attention to the basic properties of crystals - flat faces with the angles between these faces common to particular materials.
3 If an inlet tube to the evacuated bottle can be opened under some coloured water, seeing the water rush into the bottle makes an unforgettable impression.
This experiment was safety-checked in January 2005