Earth Materials

1. Earth Materials O Griffiths Heolddu Comprehensive School

2. Limestone Limestone + sand + soda glass Limestone is a __________ rock made up of mainly calcium carbonate. It’s cheap and easy to obtain. Some uses: 1) Building materials – limestone can be quarried and cut into blocks to be used in _______. However, it is badly affected by ____ ____. 2) Glass making – glass is made by mixing limestone with _____ and soda: 3) Cement making – limestone can be “roasted” in a rotary kiln to produce dry cement. It’s then mixed with sand and gravel to make _______. Words – sand, building, sedimentary, concrete, acid rain

3. Limestone If soil is too _____ crops will fail. Limestone can also be used as a neutralising agent. There are two reactions to know: 1) Firstly, a THERMAL _________________ reaction is used to break the calcium carbonate down into calcium oxide (quicklime) and _______ __________: HEAT Calcium carbonate calcium oxide + carbon dioxide 2) This is then “slaked” with water to produce calcium hydroxide (“_________ lime”): WATER Calcium oxide calcium hydroxide Calcium hydroxide is alkaline and is used to ______ acidic soil. Words – slaked, acidic, neutralise, decomposition, carbon dioxide

4. Formation of oil and gas 1) Layers of dead sea _____ settle on the seabed. 2) Layers of __________ rock build up on top. 3) The heat and ________ from these rocks, along with the absence of ______, mean that oil and gas are formed over ______ of years. Words – sedimentary, millions, oxygen, creatures, pressure

5. Hydrocarbons and crude oil H H C C H H H H Ethane Increasing length H H H H C C C C H H H H H H Butane Crude oil is a mixture of a very large number of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples: Longer chains mean… Less ability to flow Less flammable Less volatile Higher boiling point

6. Fractional distillation Fractions with low boiling points condense at the top Fractions with high boiling points condense at the bottom Crude oil can be separated by fractional distillation. The oil is evaporated and the hydrocarbon chains of different lengths condense at different temperatures:

7. Cracking Butane Ethane Ethane For example, this bond can be “cracked” to give two of these: Shorter chain hydrocarbons are in greater demand because they burn easier. They can be made from long chain hydrocarbons by “cracking”:

8. Cracking This is a THERMAL DECOMPOSITION reaction, with clay used as a catalyst Cracking is used to produce plastics such as polymers and polyethanes. The waste products from this reaction include carbon dioxide, sulphur dioxide and water vapour. There are three main environmental problems here: • Carbon dioxide causes the _________ effect • Sulphur dioxide causes _____ _____ • Plastics are not _____________

9. Alkanes Ethane Butane • Alkanes are SATURATED HYDROCARBONS. What does this mean? • HYDROCARBONS are molecules that are made up of hydrogen and carbon atoms • SATURATED means that all of these atoms are held together by single bonds, for example: Alkanes are fairly unreactive (but they do burn well).

10. Alkenes ALKANES ALKENES Ethene Ethane Butane Butene Alkenes are different to alkanes; they contain DOUBLE COVALENT bonds. For example: This double bond means that alkenes have the potential to join with other molecules – this make them REACTIVE. We can test for alkenes because they turn bromine water colourless.

11. Making Ethanol • By reacting ethene with steam in the presence of a …………………… , ethanol can be produced. • Ethanol is used …

12. Monomers and Polymers Ethene This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION Here’s ethene again. Ethene is called a MONOMER because it is just one small molecule. We can use ethene to make plastics… Step 1: Break the double bond Step 2: Add the molecules together:

13. Another way of drawing it… H H H H C C C C H H H H Ethene Ethene Poly(e)thene H H H H C C C C H H H H n C C n C C C C CH3 CH3 H H e.g. n C C n H H H H Instead of circles, let’s use letters… General formula for addition polymerisation:

14. Polymers • The properties of polymers depend on what they are made of and the conditions under which they are made. • E.g. Slimes with different viscosities. • List some uses of polymers.

15. Problems with polymers • Many ………………………… are not ………………………………. This means that they are not ………… ………… by …………………………. This can lead to problems with …………… disposal. Such as: • - • - • - • - • -

16. Evolution of the Earth’s Atmosphere Carbon Methane Ammonia Oxygen Nitrogen Others dioxide 4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2

17. Evolution of the Earth’s Atmosphere Volcanic activity releases CO2, methane, ammonia and water vapour into the atmosphere. The water vapour condenses to form oceans. 4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day Green plants evolve which take in CO2 and give out oxygen. Carbon from CO2 becomes locked up in sedimentary rocks as carbonates and fossil fuels. Methane and ammonia react with the oxygen and nitrogen is released. Nitrogen is also produced as a result of denitrifying bacteria on nitrates from decaying plants. Some of the oxygen is converted into ozone. The ozone layer blocks out harmful ultra-violet rays which allows for the development of new life.

18. Carbon dioxide in the atmosphere The amount of CO2 in the atmosphere is affected by 3 things: 1) Geological activity moves carbonate rocks deep into the Earth and they release ______ _______ into the atmosphere during volcanic activity. 2) When fossil fuels are burned the carbon contained in them reacts with _____ to form CO2. 3) Increased CO2 in the atmosphere causes a reaction between it and _______. These reactions produce two things: INSOLUBLE CARBONATES (which are deposited as ______) and SOLUBLE HYDROGENCARBONATES (which ________ in the seawater). These reactions do not remove ALL of the new CO2 so the greenhouse effect is still getting _______! Words – oxygen, seawater, carbon dioxide, worse, dissolve, sediment

19. The Structure of the Earth A thin crust - 10-100km thick A mantle – has the properties of a solid but it can also flow A core – made of molten nickel and iron. Outer part is liquid and inner part is solid The average density of the Earth is much higher than the crust, so the inner core must be very dense

20. Tectonic theory People once thought that the oceans and the continents were formed by shrinkage from when the Earth cooled down after being formed. Alfred Wegener proposed something different. Consider Africa and South America: These continents look like they “fit” together. They also have similar rock patterns and fossil records. These two pieces of evidence led me to believe that there was once a single land mass. This is my TECTONIC THEORY.

21. Movement of the Lithosphere These plates are moving apart from each other a few centimetres every _______ due to the ________ currents in the mantle caused by the ________ decay of rocks inside the core. The Earth’s LITHOSPHERE (i.e. the _______) is split up into different sections called ________ plates: Words – radioactive, crust, convection, tectonic, year

22. Tectonic theory • The Evidence: • Some continents look like they used to “fit” together • Similar rock patterns and fossil records The Problems: Wegener couldn't explain how continental drift happened so nobody believed him • The Answer: • Scientists discovered 50 years later that the Earth generates massive amounts of heat through radioactive decay in the core. This heat generated convection currents in the mantle causing the crust to move • We also now know that the sea floor is spreading outwards from plate boundaries Conclusion – scientists now believe Wegener’s Tectonic Theory

23. The Crust Sedimentary rocks settle in layers. The oldest rock is at the bottom. Layers of sedimentary rock can be examined to discover how they were formed. They are often found folded or fractured:

24. Forming mountains This is where India is now This is where India was millions of years ago The formation of mountain ranges can be explained by tectonic theory. Consider the Himalayas at the top of India: The intense heat and pressure from this process causes the rocks to change structure into metamorphic rocks.

25. Forming new crust Earthquakes and volcanic eruptions can be common here Magma

26. Movements of the crust When the lithosphere (“crust”) moves three things can happen: 1) Plates move past each other, causing earthquakes 2) Plates move away from each other – a “constructive plate margin”. The gap is filled with magma which cools to form basalt. This is called sea floor spreading. 3) Plates move towards each other – a “destructive plate margin”. The less dense one slides underneath (“subduction”) and partially melts. This causes volcanoes and earthquakes.

27. Evidence for sea floor spreading Since the Earth was formed the north and south poles have periodically “________ ____”. When tectonic plates move apart and _____ fills the gap the iron particles in the magma orientate themselves in line with the Earth’s ________ field. This means that the rock formed on the sea floor contains a “magnetic __________” of the changing field: These magnetic patterns can be used to prove that sea floor spreading does happen, and at a rate of about 2cm per _____. Words: impression, magma, swapped over, magnetic, year

28. Predicting Catastrophe • How easy is it to predict when an earthquake will happen or an volcano will erupt? We can predict ……………… earthquakes are likely to occur, but not ……………… they are likely to occur. Volcanoes usually show ………………… …………… before they erupt. Therefore it is slightly easier to predict when one might erupt.

29. Group 0 – The Noble gases

30. Group 0 – The Noble gases Some facts… 1) All of the noble gases have a full outer shell, so they are very ______ 2) They all have _____ melting and boiling points 3) They exist as single atoms rather then _________ molecules • Helium is ________ then air and is used in balloons and airships (as well as for talking in a silly voice) • Argon is used in light bulbs (because it is so unreactive) and argon , krypton and ____ are used in fancy lights Words – neon, stable, low, diatomic, lighter

31. The Periodic Table Noble gases Alkali metals Halogens These elements are metals This line divides metals from non-metals These elements are non-metals

32. The structure of the atom MASS NUMBER = number of protons + number of neutrons 4 He SYMBOL 2 PROTON NUMBER = number of protons (obviously)

33. The structure of the atom ELECTRON – negative, mass nearly nothing PROTON – positive, same mass as neutron (“1”) NEUTRON – neutral, same mass as proton (“1”)

34. Compounds Sodium chloride (salt) Methane Glucose Compounds are different to elements. They contain different atoms. Here are some examples:

35. Some simple compounds… Methane, CH4 Key Hydrogen Oxygen Carbon Sulphur Sulphuric acid, H2SO4 Carbon dioxide, CO2 Water, H2O Ethyne, C2H2