Japan 高校3年 Chemistry (part 2)

Chapters: 3

1. Inorganic substances

Inorganic substances

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Organic compounds · Polymers

Organic Compounds: Structure, Formulae and Classification – Organic chemistry is the chemistry of carbon compounds. A carbon atom has 4 outer electrons, so it always makes 4 bonds. This is called tetravalence. With 4 single bonds the carbon is sp³ and its bonds point to the corners of a tetrahedron (109.5°). With one double bond it is sp² and flat (120°). With a triple bond it is sp and straight (180°). We can draw the same molecule in several ways: complete, condensed, bond-line and 3D wedge-dash. Finally we sort organic compounds into open-chain and ring compounds, and into families by their functional group. Members of one family form a homologous series, where each member differs by one CH₂.
Polymers – A polymer is a giant molecule made by joining many small molecules (monomers) into a long chain. In addition polymerisation, monomers with a C=C double bond open up and link with nothing lost (ethene → poly(ethene)). In condensation polymerisation, two kinds of monomer with reactive groups at both ends join and give off a small molecule such as water at every link (nylon, polyester). Nature makes polymers too: starch, cellulose, proteins, DNA, rubber. Separate chains give thermoplastics that melt and can be recycled; cross-linked chains give thermosets that never melt. Most plastics do not rot, so we must reduce, reuse and recycle them.

Chemistry in human life

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