Hydraulic cylinders control the linkages in this excavator's working parts. Because the liquid (usually oil) cannot be...Read More >>Hydraulic cylinders control the linkages in this excavator's working parts. Because the liquid (usually oil) cannot be compressed, when a piston pushes down on the oil contained in a cylinder, that pressure is transmitted to the machinery. Matter exists as a solid, a liquid or a gas. It is made up of atoms of certain types (elements), either of just one type or a combination of two or more. Different materials have differing degrees of density (the amount of matter packed into a certain volume), strength, elasticity (stretchiness) and plasticity (the extent to which its shape can be changed). Other properties include: how well it conducts heat and electricity, whether it is soluble or not and what its boiling and melting points are.
Candlewax is a good example of a molecular solid. In this type of solid, the linkages between the molecules are weak. As a...Read More >>Candlewax is a good example of a molecular solid. In this type of solid, the linkages between the molecules are weak. As a result, molecular solids are plastic (malleable) when heated only slightly. They have low melting points: for waxes, this is around 45°C (113 °F). Waxes come from plants, bees and the distillation of petroleum.
In any liquid or solid, forces are needed to hold neighbouring molecules together. These forces both attract and repel other molecules. Without attractive forces, the molecules would not come together to form liquids or solids; the molecules would drift apart freely and everything would be gas. But without repulsive forces all matter would squash closer and closer together into an incredibly dense point. So, for any material, a combination of push-pull forces are at work between its molecules. These are called intermolecular forces. Many properties of solids and liquid depend on them.
Rubber is highly elastic, but at extremely low temperatures it becomes brittle, shattering into fragments if tapped with a hammer.
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