Core Chemistry - Topic 2 Materials From The Earth
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- Created by: Katie
- Created on: 05-05-13 16:12
Rocks and their Formation
- Igneous rocks - rocks formed by cooled, solidified magma
- they contain interlocking crystals of different sizes
- the size depends on the rate in which the magma cooled
- slower rate = bigger crystals
- longer time allows for them to grow
- Sedimentary rocks - rocks formed from pieces of other rocks or hard parts of dead organisms
- formed from sea shells made mostly of calcium carbonate e.g. chalk, limestone
- layers of sediment build up on the sea bed and compact together over a long time
- may contain fossils - remains of dead organisms or imprints e.g. footmarks
- Metamorphic rocks - rocks formed by heating and/or pressurising existing rocks
- marble is formed from chalk or limestone
- the small gaps between the grains become new crystals of calcium carbonate that interlock tightly
- meaning it is harder than chalk or limestone
- Sedimentary rocks are the most susceptible to erosion
- the interlocking crystals make rocks harder and less erodible
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Limestone and its Uses
- Limestone is used:
- as blocks to construct buildings 57%
- a raw material to manufacture cement, concrete and glass 38%
- making steal and iron alloys 5%
- Limestone - out of the ground at a quarry
-
- explosives used to break limestone into pieces
- cut or crushed into useful size and exported
- Thermal decomposition - strongly heating a compound so it decomposes
- calcium carbonate - calcium oxide + carbon dioxide
- Cement - heating limestone with powdered clay
- found in mortar (used to hold bricks together)
- Concrete - mixing cement with sand, gravel and water
- used in construction of buildings/bridges
- Glass - heating limestone with sand and sodium carbonate
- chemical reaction occurs liquid glass is made
- it cools and forms a hard transparent solid
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Advantages & Disadvantages of Quarrying Limestone
- Advantages
- provides jobs in difficult places (countryside)
- helps local families and businesses
- its valuable so helps local and UK economy
- provides a nature reserve after work is done
- Disadvanages
- ruin attractive scenery
- dust and noise pollution
- affect quality of life for locals
- damage tourist industry
- heavy lorries
- extra traffic - pollution
- land used cannot be used for farming etc
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Chemical Reactions
- Atoms - smallest part of an element that can take part in chemical reacions
- they make up all substances
- Compound - atoms of 2 or more different elements chemically joined together
- Chemical formula - shows symbols for elements present and ratios in which the are present
- No atoms are created or destroyed in chemical reactions just rearranged ALL REACTIONS
- total mass before = total mass after
- The products have diffeent physical and chemical properties than the reactants
- because their atoms are combined differently
- Precipitation reactions - when soluble substances react together to form an insoluble product
- called the precipitate
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Reactions of Calcium Compounds
- Calcium oxide - one product of the thermal decomposition of limestone
- calcium oxide + water = vigorous reaction making calcium hyrdoxide
- releases lots of heat
- calcium hydroxide - crumbly white solid
- Limewater - calcium hydroxide dissolved in more water
- turns from colourless to cloudy in presence of carbon dioxide
- calcium + carbon ➝ calcium + water
- hyrdroxide dioxide carbonate
- If a lot of carbon dioxide is bubbled through limewater - calcium carbonate disappears
- colourless solution is formed
- because carbon dioxide dissolves in water forming an acid solution
- acid reacts with calcium carbonate
- Farmers may spray one on their crops as plants don't like acidic soil
- Sulfur in coal - burns and produces sulfur dioxide (and nitrogen oxides)
- both acidic gases that produce acid rain
- wet calcium carbonate sprayed through waste gases to neutralise
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