Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Next page Next page The units in this module are: C2a – Paints and Pigments C2b – Construction Materials C2c – Does the Earth move? C2d – Metals and Alloys C2e – Cars for Scrap C2f – Clean Air C2g – Faster or Slower 1 C2h – Faster or Slower 2 Click on the links to take to the topic you wish to revise. Next page What’s in a paint? How paints dry What is a colloid? Thermochromic paints Download podcast here Phosphorescent paints Main menu Next page What’s in a paint? Paints have different ingredients in them to do different jobs Reason Pigment To provide colour Binding agent Keeps the paint attached to the surface solvent Dissolves the pigment and binding agent Back to C2a Main menu How paints dry Next page Water based paints such as emulsion paints dry because the solvent evaporates and forms a film Oil based paints dry because the solvent evaporates and the binding agent reacts with oxygen and harden to form a film of paint Back to C2a Main menu What is a Colloid? Next page Paint is a mixture called a colloid A colloid is where solid particles are mixed with liquid particles but do not dissolve. The solid particles are dispersed in the liquid. They are so small that they do not settle on the bottom and stay mixed. Back to C2a Main menu Thermochromic paints Next page There are some special types of paints available. Some paints contain pigments that change colour as temperature changes These are called thermochromic paints Uses of these paints include: thermometers cups kettles baby spoons eggs Back to C2a Main menu Next page Phosphorescent paints Some paints can glow in the dark. They contain phosphorescent pigments. These pigments absorb and store light energy. Uses : dash boards warning signs Before phosphorescent pigment were used, radioactive materials were used on watch faces to make them glow Back to C2a Main menu For a paint you need a pigment Blend the powder with an oil Thin it with a little solvent Stir it well but do not boil Paint it on, this is your colloid Let the solvent blow away It’s the same with an emulsion Of two liquids, one will stay Left behind the binding medium Sticks the colour to the wall Forms a smooth protective layer Doesn’t look too bad at all Dyes and paints can make a statement Dress up as a ghost or sprite Use some paint that’s phosphorescent Lit by day, it glows by night Choose a colour that’s synthetic If you want to paint the town Or wear the latest thermochromic Heat – or cold – will change it round Next page Click here to take you to a quiz on “Paints and Pigments” Back to C2a Main menu Next page Which materials are used? Products from rocks Using limestone Making concrete Download podcast here Problems with rocks Main menu Which materials are used? Next page Lots of materials can be used in buildings Some examples are : glass bricks steel aluminium wood iron Back to C2b Main menu Products from rocks Next page Limestone, granite and marble are three rocks which can be used as construction materials. Limestone Sedimentary rock Made by sea creatures sinking to the bottom of the sea and buried Granite Igneous rock Formed when molten rock cools down Marble Metamorphic rock Made by action of heat and pressure on limestone Back to C2b Main menu Next page Heating limestone Limestone is calcium carbonate, CaCO3 Heating limestone is a thermal decomposition reaction. Two new substance are made in this reaction Calcium carbonate Calcium oxide + Carbon dioxide CaCO3 CaO + CO2 Back to C2b Main menu Making concrete Next page A lot of limestone is made into cement. Limestone and clay are heated together. Concrete is a useful construction material. It is made from cement, sand, gravel and water. Concrete is not very strong unless it is reinforced. Putting steel rods in concrete reinforces it. This makes the beams stronger and prevents its from cracking. Back to C2b Main menu Next page Problems with rocks Obtaining rocks from a quarry can cause environmental problems They take up valuable land space They destroy landscapes Destroy the environment of plants and animals Increase dust and noise levels Back to C2b Main menu Next page Click here to take you to a quiz on “Construction Materials” Back to C2b Main menu Next page Structure of the Earth Plate tectonics Evidence for plate tectonics Subduction Download podcast here Volcanoes Main menu Structure of the Earth Next page Crust is solid rock Mantle is molten rock Outer core is liquid iron and nickel. It is very dense. Inner core is solid iron and nickel. It is very dense. Back to C2c Main menu Plate tectonics Next page The crust and the upper mantle is called the lithosphere. The lithosphere is made up of large sections called tectonic plates. These plates float on top of the mantle. They move a few cm each year. The liquid in the mantle can move because of convection currents and carry the plates with it. Back to C2c Main menu Evidence for plate tectonics Next page Africa and South America look like they fit together suggesting they were once joined. Fossils and rocks have been found on both continents. Earthquakes and volcanoes occur where plates meet. Back to C2c Main menu Subduction Next page When an oceanic plate and a continental plate collide, the oceanic plate is forced underneath the continental plate. The oceanic plate melts in the magma. This is called subduction. The continental plate forms fold mountains. Back to C2c Main menu Volcanoes Next page Volcanoes are formed where there are weaknesses in the Earth’s crust. Molten rock can make its way to the surface. Geologists study volcanoes. People choose to live near volcanoes because the land is fertile and lots of crops can be grown. There are two types of volcanic rock Extrusive igneous rocks form outside the Earth and have small crystals Intrusive igneous rocks form in side the Earth’s crust and have large crystals Back to C2c Main menu Next page Click here to take you to a quiz on “Does the Earth move?” Back to C2c Main menu Next page Extracting copper Purifying copper Alloys Smart alloys Download podcast here Main menu Next page Extracting Copper Copper is a useful metal used in wires and pipes Copper is extracted from its ore using displacement with carbon. This is because carbon is more reactive than carbon Copper oxide + Carbon Copper + Carbon dioxide 2 CuO + C 2 Cu + CO2 Back to C2d Main menu Purifying copper Next page Copper can be purified using electrolysis. It must be 99.9% pure to be used in wires. Rods called electrodes are placed in an electrolyte (copper sulphate) Copper metal forms on the cathode Cu2+ + 2e- Cu Copper from the anode becomes ions in solution Cu – 2e- Cu2+ Back to C2d Main menu Next page Alloys An alloy is a mixture of elements where at least one is a metal. Metals are more useful as alloys. Alloy Main Metal Use Amalgam Mercury Tooth fillings Brass Copper & Zinc Hinges, screws, instruments Bronze Copper & Tin Statues Solder Tin & Lead Joining metals, circuits Steel Iron Car bodies, ships Back to C2d Main menu Smart Alloys Next page Smart alloys are also known as shape memory alloys. Shape memory alloys can return to their original shape when put in hot water or an electric current is passed through it. Uses of shape memory alloys are: originally for military uses medical uses spectacle frames Back to C2d Main menu Next page Click here to take you to a quiz on “Metals and Alloys?” Back to C2d Main menu Next page Corrosion of iron Corrosion of aluminium Properties of iron and aluminium Car bodies Download podcast here Main menu Corrosion of Iron Next page Iron is the only metal that rusts. Iron needs oxygen and water to rust. Rusting is speeded up by salt water or acid rain. Iron + Oxygen + Water Hydrated Iron Oxide Back to C2e Main menu Corrosion of Aluminium Next page Aluminium does not corrode even in damp conditions. This is because it forms a layer of aluminium oxide. This prevents the surface from corroding. Back to C2e Main menu Properties of Iron and Aluminium Next page Property Iron Aluminium Density Denser than steel Lees dense than iron Magnetism Magnetic Not magnetic Corrosion Rusts easily Does not corrode easily Malleability Malleable Malleable Conductivity Good conductor Good conductor Back to C2e Main menu Car Bodies Next page Steel is used to make car bodies. It is harder and stronger than iron. It is also less likely to corrode than iron. Stainless steel was used to make a car body. It is more expensive than steel but did not rust. Aluminium can be used instead of steel. Aluminium cars are lighter and give better fuel economy. An aluminium frame also corrodes less, However, repair costs are approximately 25% more than steel. Back to C2e Main menu Next page Click here to take you to a quiz on “Cars for Scrap?” Back to C2e Main menu Next page Composition of air Evolution of the atmosphere Air pollutants Controlling air pollution Download podcast here Main menu Composition of Air Next page Air is a mixture of gases. It is:- 78% nitrogen 21% oxygen 1% other gases The other gases include carbon dioxide, water vapour and argon. Back to C2f Main menu Evolution of the Atmosphere Next page The atmosphere has remained constant for millions of years. Atmosphere formed from volcanic eruptions was made of carbon dioxide, water vapour, methane and ammonia. Water vapour cooled and formed oceans. Plants form and convert carbon dioxide into oxygen Back to C2f Main menu Air Pollutants Next page Pollutant How is it formed? Problem Carbon monoxide Formed from incomplete combustion in car engines Is a poison and prevents oxygen transport around body Nitrogen oxides In car engines from the reaction of nitrogen with oxygen Creates smog, acid rain and breathing problems Sulphur dioxide Combustion of fossil fuels containing sulphur e.g. coal Acid rain Back to C2f Main menu Controlling Air Pollution Next page The balance between carbon dioxide and oxygen can be changed by humans Increasing energy use means more carbon dioxide Population increase means more carbon dioxide Deforestation means more carbon dioxide Catalytic converters can be fitted to car exhaust systems to change poisonous carbon monoxide and nitrogen oxides into carbon dioxide and nitrogen. Back to C2f Main menu Next page Click here to take you to a quiz on “Clean Air?” Back to C2f Main menu Next page What are rates? Measuring rates Rates and graphs Temperature and rates Download podcast here Concentration and rates Main menu What are Rates? Next page Chemical reactions are different. The rate of reaction is the time it takes for a reaction to complete. Back to C2g Main menu Measuring Rates Next page We can measure the rate of reaction by timing how long it takes for a product to form (e.g. a gas) or a reactant to be used up (e.g. a solid) Back to C2g Main menu Rates and Graphs Next page The graph starts steeply. This is when the reaction is fastest. When the line is flat, the reaction has stopped. We can compare two reactions. The one with the steepest line is the quickest reaction. We can calculate initial rate of reaction by working out the gradient = volume of gas(cm3) time(s) Back to C2g Main menu Temperature and Rates Next page Particles of reactants must collide for a reaction to occur. As the temperature is increased the particles move faster because they have more energy. This means the particles collide more often and with enough energy. More collisions mean a faster reaction. Back to C2g Main menu Concentration and Rates Next page As the concentration is increased there are more particles in a given volume. The particles are closer together There will be more collisions and the reaction will be faster. Back to C2g Main menu Next page Click here to take you to a quiz on “Faster or Slower 1?” Back to C2g Main menu Next page Surface area and rates Catalysts and rates Download podcast here Main menu Surface Area and Rates Next page If we break up a solid reactant into smaller pieces, we increase the surface area. Because more surface area is exposed, the particles collide more frequently. More collisions mean a faster reaction. Back to C2h Main menu Catalysts and Rates Next page Catalysts are chemicals which speed up a chemical reaction. They are not used up during a reaction and do not change how much product is made, they just make it happen faster. Catalyst are specific – each catalyst only works for certain reactions Back to C2h Main menu Next page Click here to take you to a quiz on “Faster or Slower 2?” Back to C2h Main menu