Intervention session 4

1. Intervention session 4 1.The changing world Keywords: Suggest, Use information, Explain, Conclude, Calculate, Describe, Evaluate

2. Learning Objectives: • Understand what different questions are asking. • Know what answers are expected by AQA. I will be successful in this lesson if I can: • State what information is required to answer AQA set questions (Grade C) • Explain what ‘understanding’ questions are asking for (Grade C). • Identify the language sought for when answering examination questions (Grade B). • Structure long answers appropriately (Grade A).

3. 5 mins: On your own write down as many bits of information that you think belongs in that question. 10 mins: Swap your paper with your partner and add to their paper. starter

4. Speak to others in the room to find the answers to the questions that you have no bits of information on. Task 1 Please no more than 5mins

5. Let’s review the key points for The changing world 1 Task 2 • The earth is made up of layers (crust, mantle, inner and outer core). • Scientists previously thought that mountains and valleys formed by the earth shrinking (the crust wrinkled). • The earth’s lithosphere (ocean & land-crust & upper part of the mantle) is cracked into plates called tectonic plates. Convection currents set up by the heat in the mantle (caused from the natural radioactivity in the earth) has an effect on these plates by moving them either together or apart ata rate of 2.5cm per year. • Mountains form, volcanoes and earthquakes occur at plate boundaries. • Alfred Wegener’s theory of continental drift was not accepted for many years. • Volcanoes released most of the gases that formed the earth’s early atmosphere. These were mainly carbon dioxide & some water vapour.

6. Let’s review the key points for The changing world 2 Task 2 • This water vapour is thought to have formed the oceans as the earth cooled. Overtime plants evolved to produce oxygen & take in carbon dioxide setting up an O2-CO2 balance. • The main gases in today’s atmosphere are nitrogen (78%) & oxygen (21%). There are also small amounts of other gases including carbon dioxide (0.04%), noble gases – meaning unreactive because they have a full outer shell of electrons- (almost 1%) and water vapour. • The carbon cycle maintains the level of carbon dioxide in the atmosphere naturally because carbon moves into the atmosphere from respiration, decomposition & combustion. Carbon is removed from the atmosphere by photosynthesis & by dissolving in water (mainly oceans). • We are releasing the carbon from fossil fuels very quickly when compared with the millions of years it takes to produce these fossil fuels. This is why the amount of carbon in the atmosphere has been steadily increasing from human impact.

7. ASSESSOR TIPS • The inner core is solid whilst the outer core is liquid. • Alfred Wegener proposed the idea of continental drift (plates moving at a steady rate due to convection currents in the mantle set up due to natural radioactivity from the earth) in 1915. Other scientists did not accept his ideas. Eventually in 1960s, scientists found new evidence deep down on the ocean floor and Wegener’s ideas were used to develop the Theory of Plate Tectonics (the eart is broken into plates) • There are alternative theories about the earths formation & the early atmosphere, but many scientists think the current theory is accurate. There was little or no oxygen in the early atmosphere. • Make sure you know the percentages of CO2, O2, N2 in the atmosphere. • You must understand the main processes that add or remove carbon dioxide & how they work to maintain balance. • You should know what these words mean and how to use them in questions; • Photosynthesis, respire, decompose, combustion, dissolves

8. Let’s review the key points for Products from oil Task 3 • Cracking of fractions from crude oil produces smaller more useable molecules. Alkanes and unsaturated hydrocarbons (called alkenes) are produced. Bromine water is used to test for saturation. • Monomers are small molecules that join together to make polymers. Polymers are made when any type of monomer is joined together • Alkene molecules are joined together by addition polymerisation. • Polymers have very long molecules with strong bonds holding the atoms together within the molecules. • Thermosoftening polymers have weak forces between the polymer molecules. • Strong bonds form between the molecules in thermosetting polymers. • Polymers can be designed with specific properties. • New polymers have been produced to replace traditional materials in many uses. • Shape memory polymers return to their original shape after being bent.

9. ASSESSOR TIPS • Make sure you use the correct words to describe the results of the bromine water test (it turns colourless or colour is removed). • Unsaturated means that the molecules contains fewer hydrogen atoms than an alkane molecule with the same number of carbon atoms. • In addition reactions there is only one product because the reactants join together. • You should be able to recognise alkenes used as monomers from their names or formulas. • Many students do not make clear in their answers whether they are explaining the chemical or intermolecular bonds. Chemical bonds are strong and join atoms together to make molecules. Intermolecular forces act between molecules & are weaker than chemical bonds. It is best to use the word ‘bond’ only for forces that hold atoms together within molecules. • Thermosoftening plastics become soft when heated. • You DO NOT NEED TO REMEMBER the names & details of specific polymers. But YOU DO NEED TO RECOGNISE the type of polymer from a description of their properties or uses. • You should be able to explain why polymers have replaced other materials

10. Let’s review the key points for Plant oils Task 4 • Vegetable oils can be extracted from seeds, nuts and fruits by pressing or by distillation. • Vegetable oils provide a lot of energy as foods or fuels. • Some vegetable oils are unsaturated because their molecules contain carbon-carbon double bonds. • When foods are cooked in oil the energy content, flavour, colour & texture of the food are changed. • Unsaturated oils can be made into solids at room temperature by hydrogenation (addition reaction where hydrogen is added to break the double bonds & a catalyst to increase the rate of reaction and a high temperature). • Emulsions are mixtures of tiny droplets of liquids suspended in each other. Emulsifiers help to stabilise emulsions which are usually thicker than the liquids that make them. • Additives are used in foods to improve appearance, taste and shelf-life and can be identified by using chemical analysis. • E-numbers are given to foods approved for use in Europe. • We can burn vegetable oils to produce energy. Modified vegetable oils can replace some of the fossil fuels that we use because biofuel is renewable & causes less pollution.

11. ASSESSOR TIPS • There are lots of different vegetable oils, but they all have molecules with chains of carbon atoms. • Increasing the temperature makes chemical reactions go faster (increases the rate of reaction) so food cooks faster in oil than in water. • Oils are liquid at room temperature whereas fats are solid at room temperature. • Emulsions are different from solutions. In a solution the substances mix thoroughly and the liquid becomes clear. In an emulsion the liquids remain as tiny droplets and the mixture is transparent. • Liquids that DO NOT MIX and usually separate from each other are known as ‘immiscible’ and can be made into emulsions. • Questions are likely to be about the reason for adding substances to food and how these are detected. You DO NOT NEED to know specific E-numbers, but you should recognise that a substance is a permitted additive if it has an E-number. • Get used to reading food labels so you can recognise additives. For higher grades you need to be able to present arguments for and against the use of additives in foods. • You must identify that biofuels have a neutral burn. The amount of carbon put into the air is neutralised by the amount of carbon the plants had removed.

12. Learning Objectives: • Understand what different questions are asking. • Know what answers are expected by AQA. I will be successful in this lesson if I can: • State what information is required to answer AQA set questions (Grade C) • Explain what ‘understanding’ questions are asking for (Grade C). • Identify the language sought for when answering examination questions (Grade B). • Structure long answers appropriately (Grade A).