- All substances are made of atoms.
- Elements contain only one type of atom.
- Different atoms can bond together giving, taking or sharing electrons to form compounds.
- Limestone is made mainly of calcium carbonate.
- Limestone is widely used in building.
- Limestone breaks done when we heat it strongly to make quicklime and carbon dioxide.
- Some carbonates decompose when we heat them in a Bunsen flame.
- When water is added to quicklime it produces slaked lime.
- Lime mortar is made by mixing slaked lime with sand and adding water.
- Cement is made by heating limestone with clay in a kiln.
- Concrete is made by mixing crushed rocks, cement and sand with water.
- Glass is made by heating powdered limestone, sand and sodium carbonate together very strongly.
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- The Earth's crust contains many different elements.
- A metal ore contains enough of the metal to make it economically worth extracting
- The reactivity series is useful in deciding the best way to extract a metal from its ore.
- Metal more reactive than carbon cannot be extracted from its ore using carbon (you have to use electrolysis).
- We extract iron from iron ore by reducing it with carbon in a blast furnace.
- The solid, raw materials used to make iron are iron ore, coke and limestone.
- Pure iron is too soft for it to be useful.
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- Carefully controlled quantities of elements are added to iron to make alloys of steel with different properties.
- The hardness of steels is related to their carbon content.
- Alloys are mixtures of metals, designed to improve their properties.
- Smart alloys, also called shape memory alloys, return to their orginal shape on heating (used in medicine and dentistry).
- Copper and aluminium are all alloyed with other metals to make them more useful.
- Scientists are looking at new ways to extract copper that will use less energy.
- Aluminium and titanium are useful because they resist corrosion but they are expensive to extract.
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