Solid A solid is a substance in which the molecules do not have free movement. Solution A solution is a homogeneous mixture of substances that cannot be separated by mechanical means. A stalactite is a mass of calcareous matter hanging in caves, formed by the filtration of water containing calcium bicarbonate in solution through holes or pores in the cave roof. Stalagmite A stalagmite is similar to a stalactite , but grows upwards from the cave floor, usually below a stalactite. Steel Steel is an alloy of iron and carbon .
Sterling silver is an alloy of silver and copper .
Stone Age Stone Age is the name in anthropology for the period of human culture before the discovery and use of metal when man made his tools and weapons mainly of flint , but sometimes of other stones, and later of bone, horn and ivory or wood. The stratosphere is that region of the upper atmosphere where the temperature ceases to fall with increasing height above the earth's surface, and either remains constant or slightly increases. Stratified rocks are mostly sandstones, shales and limestone . Strontium Strontium is a metal element with the symbol Sr of the alkaline-earth group. Sulphuric Acid Sulphuric acid has the formulae H2SO4.