Matter & Energy


Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.

Tin

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Tin, symbol Sn, metallic element that has been used by people since ancient times. Tin is in group 14 (or IVa) of the periodic table. The atomic number of tin is 50.

Tin has been found in the tombs of ancient Egyptians and was exported to Europe in large quantities from Cornwall, England, during the Roman period. The ancient Egyptians considered tin and lead different forms of the same metal.

PROPERTIES AND OCCURRENCE

Tin is highly ductile and malleable at a temperature of 100° C (212° F). It is attacked by strong acids. Ordinarily a silver-white metal, at temperatures below 13° C (55° F) it often changes into an allotropic (distinctly different) form known as gray tin, which is an amorphous, grayish powder with a specific gravity of 5.75. Because of the mottled appearance of tin objects undergoing this decomposition, the action is commonly referred to as tin disease or tin pest. Ordinary bar tin, when bent, issues a crackling sound called tin cry, caused by the friction of the tin crystals.

Tin ranks 49th in abundance of the elements in the earth's crust. Ordinary tin melts at about 232° C (about 450° F), boils at about 2260° C (about 4100° F), and has a specific gravity of 7.28. The atomic weight of tin is 118.69.

USES

Tin is a widely sought metal and is used in hundreds of industrial processes throughout the world. In the form of tinplate, it is used as a protective coating for copper vessels, various metals used in the manufacture of tin cans, and similar articles. Tin is important in the production of the common alloys bronze (tin and copper), solder (tin and lead), and type metal (tin, lead, and antimony). It is also used as an alloy with titanium in the aerospace industry and as an ingredient in some insecticides. Stannic sulfide, known also as mosaic gold, is used in powdered form for bronzing articles made of plaster of paris or wood.