Calx     It was believed to be an ash-like substance which is left when the phlogiston leaves a metal. Although we now believe that metals form metal oxides when they burn, we no longer believe the phlogiston theory.

Carbon dioxide     This is a slightly acidic gas that is formed whn carbon burns in air (or oxygen). It does not support combustion and so a burning splint will be extinguished by the gas. However, this is NOT the test for carbon dioxide. To test for the gas, bubble it into limewater. A milky white precipitate shows that the gas is carbon dioxide.

Carbon dioxide is produced during respiration (this is true whether the respiration is by animals, plants or even anaerobic respiration of yeast during fermentation).

Carbon monoxide     This has the formula CO and is a possible product if a fuel burns in a poor supply of air. It is a toxic gas. It can be removed from the exhaust gases of cars by the use of a catalytic converter. You should be able to write a word equation for its formation during a combustion reaction.

Carbon steels     Steel can contain up to 1.5% of carbon. This is much less than the 4% found in cast iron.

Cast iron     This is iron as it comes out of the blast furnace. It contains around 4% carbon and so is brittle. Some of the carbon is removed as th cast iron is converted to steel.

Catalytic converter     This is a device fitted to the exhaust pipe of a car in order to convert the harmful gases into less harmful ones. The particulular gases to be removed are carbon monixde and the nitrogen oxides.. Afetr conversion , these become nitrogen (already 4/5 of the atmosphere) and carbon dioxide (although a pollutant since it is a greenhouse gas, the amount of carbon dioxide released in this way is very small compared to the amount emitted by burning the fuel).

Cement     Limestone is heated to a high temperature with clay and then powdered. It is mixed with sand and water to make mortar.

Cementation     This is one of the processes of sedimentary rock formation. The water is squeezed out from the gaps between the grains of sand etc of the wet sediment. This leaves behind the mineral salts which can act as a kind of glue to hold the grains together.

Chemical equation     (Don't confuse this with chemical formula) If you are asked for a symbol equation is must be balanced.

Chemical formula     (Don’t confuse this with chemical equation) This is the chemical code for a substance. If the substance forms molecules the formula tells us how many atoms of each element are in the molecule.

Eg HCl contains one hydrogen and one chlorine
C2H5OH contains two carbons, six hydrogens and one oxygen

If the substance does not form molecules (such as ionic solids), the formula tells us the ratio of each kind of ion.

Eg NaCl has one sodium ion for every chloride ion
CuCl2 has one copper ion for every two chloride ions

Sometimes brackets can be used to make things clearer:

CuNO3 2 might mean one copper, one nitrogen and thirty two oxygens but

Cu(NO3)2 clearly means one copper, two nitrogen and six oxygens

Chemical reaction     A change where one or more new substances are formed. It is difficult to undo a chemical change.

Chemical weathering     Rocks can be broken down by many effects. Chemical weathering is where this breakdown is caused by chemical action. This is often due to acidic rainfall and is made worse when the rain is made extra acidic by pollution (acid rain).

Chromatography     Literally means coloured writing, it is a technique used to separate coloured materials. You can use chromatography to separate the colours of ink (maybe black ink contains red, blue and brown dyes) or food colourings (smarties are good for this). Forensic science uses chromatography to investigate substances found at the scene of a crime and can trace DNA etc.

Coke     Coal is heated in the absence of air (so not burned) to drive off volatile components and form coke. It is a raw material in the blast furnace as a source of carbon.

Combustion     This is a scientific word for the burning of a fuel.

Compound     A substance conatining two or more different kinds of atoms chemicaly joined together.

Concrete     This is formed by mixing cement, sand, stones (or crushed rock) and water. It can be poured into a hole to form a block for building foundations or into a mould to produce a variety of shapes (eg girders and railway sleepers). It can be reinforced by being poured around steel cables or mesh.



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