Chapter 1 Fundamental ideas
Atoms
• There are about 100 different types of atom, giving about 100 different elements.
• Each element has its own unique symbol.
• Many more substances are compounds, with two or more different elements chemically joined together.
• The chemical formula of a compound shows how many of each type of atom it contains.
• Atoms have a small, central nucleus with electrons in orbit around it.
• Protons have a positive charge, neutrons are neutral and electrons have a negative charge.
• Atoms of the same element always have the same number of protons.
Forming bonds
• Metals lose electrons to form positive ions.
• Non-metals gain electrons to form negative ions.
• Metals and non-metals form ionic bonds together.
• Non-metals can share electrons to form covalent bonds.
• Atoms are conserved during chemical reactions – they just ‘change partners’.
• This conservation is shown in balanced chemical equations.
Electron arrangement
• The electrons around an atom are arranged in energy levels (electron shells).
• The first shell holds two electrons, the others eight (for the first 20 elements).
• The elements can be arranged in a periodic table in which elements with similar properties occur in the same group.
• The group number tells you how many electrons the element has in its outer shell.
• Metals are found to the left of the table, non-metals to the right, divided by a zig-zag line.
Groups 1 and 0
• Group 1 contains very reactive metals.
• Group 1 metals react with oxygen in air, producing coloured flames.
• Group 1 metals react violently with water, giving off hydrogen gas.
• Group 0 contains the unreactive noble gases.
• Helium is used for safe airships and for party balloons.
• Argon is used to fill ‘old-style’ light bulbs.
• Neon is used in neon lights and as a very low temperature refrigerant.
Chapter 2 Rocks and building materials
Limestone
• Many raw building materials come from rocks such as limestone.
• There are many environmental and economic problems associated with digging rocks from the Earth.
• Limestone is a natural form of calcium carbonate.
• Limestone and other carbonates react with acid to produce carbon dioxide, a salt and water.
• Limestone is badly damaged by acid rain.
Limestone cycle
• Limestone (CaCO3) and other carbonates can be broken down by thermal decomposition.
• Limestone breaks down when heated to form calcium oxide.
• If you add water to calcium oxide it forms calcium hydroxide, which can be used to neutralise acid in the soil.
• Limewater, calcium hydroxide solution, turns cloudy with carbon dioxide. This is the test for carbon dioxide.
Concrete
• Limestone and clay are the raw materials of cement and concrete.
• Concrete is a very versatile building material.
• Concrete is cheap and easy to store, mix and pour into moulds of any shape or size.
• Once set, concrete is rock-hard.
Chapter 3 Metals and their uses
Metal ores
• Most metals are found in chemical compounds called ores.
• Mining ores has many social, economic and environmental effects, some positive, some negative.
• Metal ores are finite and are expensive to refine, so recycling metals makes economic sense as well as having less impact on the environment than mining.
Extracting metals
• Most metals are found as ores from which the metal must be extracted.
• Some metals are more economical to extract than others.
• Less-reactive metals, such as copper, can be extracted by carbon reduction.
• More-reactive metals, such as aluminium, must be extracted by electrolysis.
• Electrolysis on an industrial scale uses large amounts of electrical energy, so it is expensive.
Methods of extracting
• Blast furnaces have to run at very high temperatures to reduce iron oxide and melt the iron.
• Good quality copper ores are now very rare, so copper is usually made by other means.
• Acid is used to leach copper salts from ore, after which they are purified by electrolysis.
• New ideas like bioleaching, phytomining and displacement are being tried out to get copper from ores with very little copper.
Metallic issues
• Economically exploitable metal ores are finite and will run out.
• The developed world is taking more than its fair share of metal resources.
• Recycling can help to make our resources last longer – and save energy and money while reducing pollution.
• New techniques such as phytomining can be used to reclaim waste land and get more metals.
Metal uses
• Metals have many useful properties that we use in our everyday lives.
• Iron can be strong enough to build bridges and machines, yet can be rolled, pressed and cut into any shape.
• Elements in the central block of the periodic table are called transition metals.
• Transition metals can be bent or hammered into shape and are good conductors of heat and electricity.
Alloys
• The iron coming out of a blast furnace is impure and brittle and so has limited uses.
• Pure metals can be quite soft, so they are mixed with small amounts of other elements to make the metal harder.
• Alloys have different-sized atoms added. These distort the layers and stop them sliding, making the metal harder.
• Most iron is turned into its alloy steel by the addition of a little carbon; the amount of carbon controls the properties of the steel.
• Most metals are used in the form of alloys to alter their properties to suit our needs.
Chemistry UNIT 1 Key Points 1