Junior cycle science chemistry earth materials


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Junior cycle science chemistry earth materials

  1. 1. 07/03/2014 Junior Cycle Science Chemistry Earth Materials Theresa Lowry-Lehnen RGN, BSc (Hon’s) Nursing Science/ Specialist Practitioner, PGCC, Dip Counselling, Dip Adv Psychotherapy, BSc (Hon’s) Clinical Science, PGCE (QTS), H. Dip. Ed, MEd, PhD student Health Psychology
  2. 2. Limestone 07/03/2014 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: Limestone + sand + soda glass 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. 3. Limestone 07/03/2014 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 _______ __________: Calcium carbonate HEAT calcium oxide + carbon dioxide 2) This is then “slaked” with water to produce calcium hydroxide (“_________ lime”): Calcium oxide WATER calcium hydroxide Calcium hydroxide is alkaline and is used to ______ acidic soil. Words – slaked, acidic, neutralise, decomposition, c
  4. 4. Formation of oil and gas 1) Layers of dead sea _____ settle on the seabed. 2) Layers of __________ rock build up on top. 07/03/2014 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. 5. Hydrocarbons and crude oil 07/03/2014 Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples: C C H H H H H Ethane H H H H H C C C C H H H H Butane H Increasing length H Longer chains mean… 1. Less ability to flow 2. Less flammable 3. Less volatile 4. Higher boiling point
  6. 6. Fractional distillation 07/03/2014 Crude oil can be separated by fractional distillation. The oil is evaporated and the hydrocarbon chains of different lengths condense at different temperatures: Fractions with low boiling points condense at the top Fractions with high boiling points condense at the bottom
  7. 7. Cracking 07/03/2014 Shorter chain hydrocarbons are in greater demand because they burn easier. They can be made from long chain hydrocarbons by “cracking”: Butane Ethane For example, this bond can be “cracked” to give two of these: Ethane
  8. 8. Cracking 07/03/2014 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: 1) Carbon dioxide causes the _________ effect 2) Sulphur dioxide causes _____ _____ 3) Plastics are not _____________
  9. 9. Alkanes 07/03/2014 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: Ethane Butane Alkanes are fairly unreactive (but they do burn well).
  10. 10. Alkenes 07/03/2014 Ethane Ethene Butane ALKENES ALKANES Alkenes are different to alkanes; they contain DOUBLE COVALENT bonds. For example: Butene 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. 11. Monomers and Polymers Ethene 07/03/2014 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: This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION
  12. 12. Another way of drawing it… 07/03/2014 Instead of circles, let’s use letters… H H C C H C H Ethene H H C C C H H H C C H Ethene H H H H H H Poly(e)thene General formula for addition polymerisation: n C C C C n e.g. H n CH3 H CH3 C C C C H H H H n
  13. 13. 07/03/2014 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 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. 2 Billion years 1 Billion years 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. Present day
  14. 14. 07/03/2014 Evolution of the Earth’s Atmosphere Carbon dioxide 4 Billion years Methane Ammonia Oxygen Nitrogen Others Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2 3 Billion years 2 Billion years 1 Billion years Present day
  15. 15. Carbon dioxide in the atmosphere 07/03/2014 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
  16. 16. The Structure of the Earth 07/03/2014 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
  17. 17. The Crust 07/03/2014 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:
  18. 18. Movement of the Lithosphere 07/03/2014 The Earth’s LITHOSPHERE (i.e. the _______) is split up into different sections called ________ plates: 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. Words – radioactive, crust, convection, tectonic, year
  19. 19. Forming new crust 07/03/2014 Earthquakes and volcanic eruptions can be common here Magma
  20. 20. Tectonic theory 07/03/2014 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. 21. Forming mountains 07/03/2014 The formation of mountain ranges can be explained by tectonic theory. Consider the Himalayas at the top of India: This is where India is now This is where India was millions of years ago The intense heat and pressure from this process causes the rocks to change structure into metamorphic rocks.
  22. 22. The Evidence: Tectonic theory 07/03/2014 1) Some continents look like they used to “fit” together 2) Similar rock patterns and fossil records The Problems: Wegener couldn't explain how continental drift happened so nobody believed him The Answer: 1) 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 2) We also now know that the sea floor is spreading outwards from plate boundaries Conclusion – scientists now believe Wegener’s Tectonic Theory
  23. 23. Movements of the crust When the lithosphere (“crust”) moves three things can happen: 07/03/2014 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.
  24. 24. Evidence for sea floor spreading 07/03/2014 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