Presentation on theme: "The earth’s crust 3 layers: Crust, mantle and core. The mantle is mostly solid, but can move slowly The crust is cracked into tectonic plates How do tectonic."— Presentation transcript:
The earth’s crust 3 layers: Crust, mantle and core. The mantle is mostly solid, but can move slowly The crust is cracked into tectonic plates How do tectonic plates move? 1. Radioactive processes occur in the core which release heat. 2. The heat travels through the mantle by convention currents. These convection currents cause the plates to move a few cm per year If the movements are sudden, earthquakes and/or volcanoes can occur at the plate boundary When plates crash into each other, it causes mountain ranges Wegeners theory of crustal movement/ continental drift The continents were once joined by gradually moved apart. He thought this as there were similar fossils on continents that were very far apart (s america and africa) The shapes of the continents fitted He thought that the mountain ranges on the earth’s surface were caused by continents colliding. Scientists did not believe him as he could not explain how they moved What did they believe? They believed that mountain ranges were caused by the earth’s crust cooling and shrinking after it was first formed They also thought there was a land bridge (which had now sunk) between s America and Africa, which explains the fossils. Formation of the atmosphere The atmosphere is a layer of gases surrounding the earth. It is held in place by gravity During the first billions years of the earth’s existence there was intense volcanic activity. This released the gases which made up the atmosphere. One theory about the atmosphere is that… It was mostly carbon dioxide and water vapour. There was also small amounts of ammonia or methane There was little or no oxygen Earth’s Atmosphere
Today’s atmosphere The atmosphere has been the way it is today for 200 million years It is made up of mostly nitrogen (78%). It also contains 21% oxygen It contains 0.04% carbon dioxide The remainder is made up of water vapour, methane and noble gases Uses of noble gases- Helium (balloons) Neon (advertising signs) Argon (light bulbs) The differences between the early and today’s atmosphere Water vapour: There is much less water vapour now It condensed to form the oceans Carbon dioxide: There is much less carbon dioxide now. It was taken in by plants The plants died and formed layers These eventually formed sedimentary rocks (fossil fuels) It also dissolved in the oceans to form carbonate rocks. Oxygen: Produced by plants (photosynthesis) How did life begin? The Miller Urey experiment Amino acids are needed to make a living organism Amino acids are made up of carbon, hydrogen, nitrogen and oxygen Miller and Urey did an experiment to see if they could make amino acids under conditions like the early atmosphere They used water, ammonia methane and hydrogen. These did not react under normal conditions They did react when Miller and Urey used a high voltage to produce a spark. This simulated lightening This provided energy for the reaction 11 amino acids were formed This provides some evidence that lightening may have provided the energy to create life. Primordial soup theory Organic molecules (found in the sea) form a ‘primordial soup’ These then reacted together to form the first primitive cells Fractional distillation of air Fractional distillation is used to separate liquids with different boiling points. 1.Air is cooled until it condenses to a liquid (-200 C) 2.Carbon dioxide and water are removed from the mixture as they are solid at this temperature. 3.Liquid is warmed. 4.Nitrogen is collected at the top and oxygen at the bottom Uses of Nitrogen and Oxygen Nitrogen: Very unreactive so stops food going off Used to make ammonia Oxygen: Helps people breathe (accident scene or in hospital)
Vegetable Oils These are important foods as they provide us with a lot of energy and nutrients This is found in fruits, nuts and seeds To extract the oil, you need to crush the plant material and press the oil out Water and other impurities are then removed Cooking with vegetable oils Vegetable oils have a higher b.p that water This means they can be used to cook foods at higher temperatures (where the water would just evaporate) This means food can be cooked faster, and can also be flavoured differently However, oils release more energy when eaten, which turns to fat if not burned. Emulsions Some substances do not mix. They are said to be immiscible (eg oil and water). We can use an emulsifier to force them to mix. The remaining mixture is called an emulsion. Emulsions are more viscous than oil and water Emulsions provide better texture, coating ability and appearance Unsaturated oils contain C=C double bonds which can be tested for using bromine water (goes colourless as with alkenes) We can harden unsaturated oils to increase the melting temperature. This makes them solid as room temperature, which makes them useful as spreads. Hardening vegetable oils React with hydrogen at 60 ̊ C Use a Nickel catalyst to speed up the process The saturated oil is called a hydrogenated oil Plant oils
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