Chemistry Unit 1

Atoms and elements-

the nucleus contains protons and neutrons giving it an overall +1 charge yet the overall charge of the atom is neutral due to the -1 charged electrons as number of protons= electrons.

The periodic table- vertical=groups, horizontal=periods. All elements in a group have similar properties and the same number of electrons in the outer shell and you can therefore predict their properties. Group 0 are noble gases and they are stable and unreactive due to full outer shell.

Compounds-

Atoms react forming chemical bonds thus making compounds which are difficult to separate.

A metal and a non-metal is an ionic compound, and it occurs because the metal loses its extra electron making it +ve yet the non-metal gains electrons making it -ve and the opposite charges attract.

A compound make of non-metals is created by sharing electrons, and this is a covalent bond- enough covalent bonds will be made to fill up the outer shell. 

Limestone-

Limestone is retrieved through quarrying and is good for making monuments and old buildings. Limestone is known also as calcium carbonate (CaCO3).

·         When heated calcium carbonate thermally decomposes to form calcium oxide (CaO) and carbon dioxide (CO2).

·         When reacted with acid its forms a salt, carbon dioxide and water. 

·         when reacted with water only calcium hydroxide is formed (Ca(OH)2) which is an alkali that can neutralise acidic soil in fields and can test for carbon dioxide as when mixed with water it forms lime water. 

·         when heated in a kiln with clay it makes cement

·         cement+sand+water=mortar 

·         cement+sand+aggregate=concrete

Disadvantages: it destroys the landscape creating an eyesore, quarrying creates noise pollution and dust which is bad for asthmatics, habitats are destroyed, Lorries used pollute and the energy used to make products comes from burning fossil fuels.

Advantages: you can build houses and roads, it can neutralise soil and acidic lakes, it can neutralise sulphur dioxide in power stations preventing acid rain, the quarry provides local jobs and it can improve the local economy and infrastructure. 

limestone products are cheap and widely available, hardwearing, can be poured into moulds to quickly and cheaply build buildings (yet it is unattractive), they don’t rot when wet, cannot be gnawed away by insects and rodents, concrete doesn’t corrode and if fire resistant yet has to be reinforced as it can crack.

Extracting metals from rocks-

Ores must contain enough metal to be worth extracting, and the metals are in the form of oxides as they have reacted with oxygen. If the market price increases and technology improves making it easier to extract then it is worth extracting, but if prices drop then it is not.

Metals are extracted from their ores via REDUCTION or ELECTROLYSIS.

Anything below carbon (zinc, iron, tin, lead, copper, silver, gold and platinum) are removed by reduction with carbon (e.g. copper oxide+ carbon= copper + carbon dioxide)

Electrolysis: elements more reactive than carbon are removed via electrolysis of molten compounds. The…