1 - My Wider World
1.1 Our changing universe
Candidates need to understand that:
For many centuries, our ancestors thought the Earth was the centre of the universe. Science has since taught us that this is incorrect. We know that the Earth lies within the Milky Way galaxy (a group of stars), which is located somewhere within the universe. Scientists have discovered that the Sun is one star in the Milky Way. Even smaller in scale than a galaxy is a solar system. Our solar system comprises one star (the Sun) and planets orbiting it.
Scientists use many different techniques to observe and search for patterns in the universe in an attempt to understand and gather evidence concerning how it began, what it is like and how it is changing. They have gathered much evidence from the use of telescopes, both on Earth and in space, and from the study of light reaching us from stars in distant galaxies.
Candidates need to:
1. Know that observations of the solar system and the galaxies in the universe can be carried out on the Earth or from space.
2. Know that observations are made with telescopes that may detect visible light or other electromagnetic radiations such as radio waves or X-rays from space, and that these observations provide evidence for changes taking place in the universe.
3. Understand that if a wave source is moving relative to an observer there will be a change in the observed wavelength and frequency (Doppler effect).
4. Explain why there is a red-shift in light observed from most distant stars and galaxies. The further away stars or galaxies are, the more their light is red-shifted. This indicates that distant galaxies are moving away from us, and that the further away a galaxy is the faster it is moving away.
5. Explain how the observed red-shift provides evidence that the universe is expanding and supports the ‘Big Bang’ theory (that the universe began from a very small initial point).
Within this context, candidates should be able to use scientific data and evidence to discuss, evaluate or suggest implications of the following:
■ the position of the Earth in the solar system
■ the evidence for the origin, structure and continuing evolution of the universe.
1.2 Our changing planet
Candidates need to understand that:
The Earth is a planet that has changed since its formation and is still changing. The surface of the Earth has cooled after a period of intense volcanic activity and has become able to sustain plant and animal life. The surface of the Earth continues to change due to the activity of volcanoes and earthquakes, mainly along the edges of tectonic plate boundaries.
Alongside these changes the atmosphere has altered to enable life to evolve, from being rich in carbon dioxide to containing enough oxygen to support life. Environmental scientists are beginning to understand the processes that cause the natural greenhouse effect and maintain the heat balance and global climate that enable life on Earth.
Candidates need to:
1. Know that the surface of the Earth has changed over time as a result of cooling.
2. Know that the Earth consists of a mantle, core and crust, surrounded by the atmosphere.
3. Know that the Earth’s crust and the upper part of the mantle are cracked into a number of large pieces (tectonic plates).
4. Explain how convection currents within the mantle cause the movement of tectonic plates.
5. Describe how movement of tectonic plates can cause disastrous consequences such as earthquakes and volcanoes.
6. Know that during the first billion years of the Earth’s existence there was intense volcanic activity.
7. Know that volcanic activity released the gases that formed the early atmosphere and water vapour that condensed to form the oceans.
8. Understand that some theories suggest that, during this period, the Earth’s atmosphere was mainly carbon dioxide and there would have been little or no oxygen gas. HT only: there may also have been water vapour and small proportions of methane, hydrogen and ammonia.
9. Describe how plants and algae produced the oxygen that is now in the atmosphere by photosynthesis.
10. Describe how the atmosphere surrounding the Earth allows light energy radiated from the Sun to pass through.
11. Explain how greenhouse gases in the atmosphere keep temperatures on Earth stable and warm enough to support life, by allowing short-wave radiation to pass through the atmosphere to the Earth’s surface but absorbing the outgoing long-wave radiation from the Earth.
Within this context, candidates should be able to use scientific data and evidence to discuss, evaluate or suggest implications of the following:
■ the accurate prediction of earthquakes and volcanic eruptions
■ changes to the composition of the atmosphere over time.
1.3 Materials our planet provides
Candidates need to understand that:
The Earth’s crust, sea and atmosphere, and the organisms living on Earth, are the ultimate sources from which all useful substances are obtained. Metals, metal ores, limestone and fossil fuels are examples of materials obtained from the Earth. Scientists are sometimes able to use these materials directly, but many have to be processed or reacted with other substances to make useful products.
Understanding the chemical structure of these raw materials and their chemical reactions enables scientists to make the best use of them.
Candidates need to:
1. Be able to classify materials as elements, compounds or mixtures.
2. Describe the structure of the atom in terms of numbers of protons, neutrons and electrons and their arrangement. Atoms contain the same number of protons (positive charge) and electrons (negative charge). The protons and the neutrons (no charge) are at the centre, in the nucleus, and the electrons are positioned around the outside of the atom.
3. Explain the difference between atoms, molecules and ions.
4. Define the terms atomic number and mass number.
5. Know that useful materials can be removed from the ground by mining or quarrying.
6. Give examples of substances used straight from the ground (gold, sulfur, limestone and marble).
7. Describe how salt is separated from rock salt before use.
8. Describe how fuels (hydrocarbons) are separated from crude oil (fractional distillation).
9. Describe how metals are separated from their ores:
(a) metals more reactive than carbon, such as aluminium, are extracted by electrolysis of molten compounds. The use of large amounts of energy in the extraction of these metals makes them expensive
(b) metals less reactive than carbon are extracted from their ores using carbon and carbon monoxide as reducing agents
(c) lead and iron may be made from their oxides by reduction:
■ extraction of lead: carbon and carbon monoxide can act as reducing agents (2PbO + C ➞ 2Pb + CO2 and PbO + CO ➞ Pb + CO2)
■ extraction of iron: iron oxide (Fe2O3) and coke (carbon) are heated to produce iron. The coke burns to produce carbon dioxide (C + O2➞ CO2). The carbon dioxide reacts with the coke to produce carbon monoxide (C + CO2 ➞ 2CO). When heated, the iron oxide reacts with the carbon monoxide to produce iron. Iron oxide is reduced and carbon monoxide is oxidised (Fe2O3 + 3CO ➞ 2Fe + 3CO2).
10. HT only: describe air (the atmosphere) as a mixture of gases with different boiling points that can be fractionally distilled to provide new materials for industrial processes (helium for balloons, argon for filament lamps and electrical discharge tubes, nitrogen for ammonia – which is used for making fertilisers) and either used directly or used to make another product.
Within this context, candidates should be able to use scientific data and evidence to discuss, evaluate or suggest implications of the following:
■ the social, economic and environmental impacts of exploiting the Earth’s crust, sea and atmosphere, and living organisms
■ methods of cleansing coal and metal mines such as phytomining.
1.4 Using materials from our planet to make products
Candidates need to understand that:
Commercial organisations make products for consumers to buy. Chemical companies have to make profits and need to maximise the amount of product produced from the starting materials. For this reason, chemists often have to work quantitatively (ie accurately to measure the amounts of reactants and products).
When buying a product the consumer is often encouraged to think about the energy used, and waste produced, in making the product in addition to its cost and effectiveness.
Candidates need to:
1. Explain why mass is conserved in chemical reactions and that during a reaction products with different properties are formed as a result of atoms rearranging.
2. Know that, when producing new products, chemical reactions can be represented by using balanced chemical equations.
3. Explain why, in order to produce a product economically and safely, it is important that the correct amount of material is used.
Within this context, candidates should be able to use scientific data and evidence to discuss, evaluate or suggest implications of the following:
■ material costs when making products
■ costs of energy consumption when making products
■ the ‘value for money’ of a range of products.
Suggestions for practical work that could be used to support Theme 1
It is the responsibility of the centre to be aware of the health and safety implications of any practical work, and to
ensure that risk assessments for practicals are carried out.
■ Compare less reactive metals with more reactive metals, eg in acid.
■ Heat metal oxides with carbon to compare reactivity, eg CuO, PbO, Fe2O3.
■ Heat copper carbonate with charcoal to produce copper.
■ Study displacement reactions, eg CuSO4(aq) + Fe.
■ Ignition tube demonstration of blast furnace – potassium permanganate, mineral wool plug, iron oxide mixed with carbon.
■ Pass air over heated copper using gas syringes and measure the percentage of oxygen. Then burn magnesium in the nitrogen to form Mg3N2. Add water to produce ammonia (nitrogen must have come from the air).
■ Collect gas produced by aquatic plants and test for oxygen.
■ Measure the amount of carbon dioxide in inhaled and exhaled air.
■ Demonstrate fractional distillation of crude oil using CLEAPSS mixture (take care to avoid confusion with the continuous process in a fractionating column).
■ Make model volcanoes.
■ Grow brassica plants in compost with added copper sulfate or spray brassica plants (eg cabbage leaves) with copper sulfate solution, ash the plants (fume cupboard), add sulfuric acid to the ash, filter and obtain the metal from the solution by displacement or electrolysis.
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