Chemistry

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IONIC BONDING

metal & non-metal = ions

metal lose electrons = positive ions/

non-metal gain electrons = negative

COVALENT BONDING

non-metals = molecules

atoms share electrons to fill outer shells

Calcium carbonate (limestone)

thermal decomposition = calcium oxide + carbon dioxide

calcium carbonate + sulfuric acid → calcium water

calcium oxide + water → calcium hydroxide = alkali

neutralise acidic soil - faster than limestone

test for CO2 - bubble gas through limewater solution (dilute calcium hydroxide) = cloudy solution of calcium carbonate from CO2

Heated powdered limestone & powdered clay = cement

Cement mixed with sand & water = mortar (stick bricks) (can add calcium hydroxide)

Mix cement with sand & aggregate (water & gravel) = concrete

Quarrying limestone = scars landscape

big ugly holes

noise & dust

destroys habitats

transported away (lorries)

Pollution

cement factories = dust = breathing problems

energy for cement & quicklime (calcium oxide) = fossil fuels

Houses & roads/dyes paints, medicines

Neutralise - acidic soil & rivers/lakes (acid rain)

Neutralise sulfur dioxide in power station chimneys

Jobs = money into local economy = local improvements

Limestone & concrete - building materials

widely available & cheaper than granite/marble

more hard-wearing than marble but attractive

concrete poured into moulds to make blocks which join together. Quick & Cheap. But Unattractive.

Limestone/concrete/cement don't rot when wet like wood. Not gnawed by insects. Fire-resistant.

Concrete doesn't corrode. Low tensile strength - can crack. Stronger if reinforced with steel.

Thermal decomposition - when one substance chemically changes into at least two new substances when heated

Chemistry