Chemistry Unit 1

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  • Chemistry 1
    • Crude Oil
      • Crude oil, natural gas coal. Formed extremely slow. They are finite (limited supply) and non renewable (using them up faster than being formed so eventually run out)
      • Crude oil
        • Trapped in  Eaths crust. Released by hole being drilled through rock. Oil has to be under pressure to flow out.
        • When extracted is thick, black sticky liquid which is transported to a refinert through pipeline.
          • Toxic oil can coat feathers of sea birds. Oil wash ashore and damage beaches which leads to a big clean up. Detergents used to disperse oil however  toxic to widelife
      • Fractional Distillation
        • Crude oil is split into fractions containing similar sized molecules using fractional distillation. The oil is heated until it vaporises. It then passes up a tall tower that is hot at the bottom but cool at the top. As the vapour passes up this tower the molecules cool and condense
      • hydrocarbons
        • Small hydrocarbon- Small forces of attraction, easy to break by heating, volatile substance, low boiling point
        • Long hydrocarbon- large force of attraction, difficult to break by heating, think viscous liquid, higher melting point
      • Cracking
        • Converts large alkane molecules into smaller more useful alkane/alkene molecules. Smaller alkane molecules blended to make petrol (huge demand).
          • Needs catalyst and high temperature.
    • Carbon Fuels
      • Choosing a fuel
        • Energy, Value, Cost, Availability, Toxicity, Ease of use, Storage, Pollution
      • Combustion
        • Complete=   Methane + Oxygen ? Carbon dioxide + Water
          • Incomplete= Methane + Oxygen ? Carbon monoxide + Water
            • Very little oxygen=           Methane+ Oxygen  ? Carbon+ Water
    • Clean Air
      • Changing atmosphere
        • Earliest atmosphere contained ammonia and carbon dioxide. This came from inside Earth and was released through action of volvanoes
          • Temperature fell, water vapour in atmosphere condensed to form ocean+ sea
            • Evolution of plants meant  photosynthe-sis started  reduce amount  carbon dioxide + increase oxygen in atmosphere
              • Clean air,         78% nitrogen          21% Oxygen   1% other gases including 0.035% carbon dioxide
      • Pollution
        • Pollution gasses formed by Burning fossil fuels and incomplete combustion of car engine
          • Car exhausts produce Carbon monoxide, Nitrogen dioxide(leads to acid rain), unburned hydrocarbons (creates smog)
            • Oxides of nitrogen produces acid rain and photochemical smog
              • Aerosols produce CFCs (damage ozone layer)
                • A way to removie carbon monoxide from car exhaust is to fit a catalytic converts. It causes the carbon monoxide to react producing carbon dioxide
                  • carbon monoxide+     nitrogen oxide  ?    nitrogen+ carbon dioxide
      • Acid Rain
        • Coal/Oil burned sulphur impurities produce sulphur dioxide. This plus nitrogen dioxide dissolves in water to produce acid rain. Acid rain can erode stonework and corrode metals, kill plants, make rivers acidic and kill aquatic life
          • Human influences on atmosphere
            • Excessive burning of fossil fuels is increasing the amount of carbon dioxide in atmosphere. Deforestation on large areas of the Earth surface means amount of photosynthesis is reduces from the atmosphere.
    • Making polymers
      • Alkanes and Alkenes
        • Alkanes have a single covalent bond and are saturated .With bromine water is colourless (have max number of hydrocarbon atoms per carbon atom in molecule) Alkenes have double covalent bond and are unsaturated. With bromine water is orange (carbon atom is not bonded to max number of hydrogen atoms)
      • Polymerisation
        • Alkenes made by cracking can be used as monomers. These are small molecules that can be reacted to make polymers. Alkenes are good at joining together and when they dont produce another substance it is polymerisation
          • The process needs high pressure and catalyst.
            • Addition Polymerisation
              • Involves reaction of any unsaturated monomer molecules eg alkenes to form a saturated polymer
    • Designer Polymers
      • Polymer plastic properties
        • Easily molded, Waterproof, Electrical insulator, Non- biodegradable, Lightweight, Flexible, Can be printed on, Unreactive.Can be coloured, Heat insulator, Transparent, Tough
          • Outdoor clothing- Nylon. Because its light weight, tough, waterproof (dosnt let vapour escape so it could be uncomfortable to wear is person gets hot and perspire.)
            • Gore-tex is a breathable material with all advantages of nylon but allows water vapour to escape but prevents rain from getting in. It has a membrane of polyurethane sandwiched between 2 layers of nylon fibres, The polyurethane has tiny holes that allow vapour to pass through but that are too small to let liquid vapour though.
              • The structure of plastics is that the consist of a tangles mass of very long chain molecules in which atoms are held together by strong covalent bonds. Plastics that have weak forces between polymer molecules have low melting points and can be stretched easily as the polymer molecules can slide over one another. Plastics that have strong forces between the molecules have high melting points, rigid+ can't be streached
      • Disposal  of plastics
        • Landfills sites. Problem because most plastics are non-biodegradable. Therefore micro-organisms have no effect on them and will not decompose+   rot away. Waste of land
          • Burning plastics. Produce air pollution+waste valuable resoucres. Produce carbon dioxide (greenhouse effect) leads to global warming
            • Recycling plastic. Prevents resources being wasted. However different types of plastic need to be recycled separately. Therefore time consuming.
    • Cooking + Food Additives
      • Cooking food
        • Causes a chemical reaction to occur, (new substances formed from old ones, change in mass, energy change, rise/fall in temperature
          • Eggs and meat contain protein, the protein molecules change shape shape when they are heated denaturing. Therefore texture changes.
            • Potatoes and other vegetables are plants and their cells have rigid cell walks. During cooking the heat breaks down this cell wall, starch is released and it becomes softer. The starch grains swell up and spread out, this makes the potato is easier to digest
      • Baking Powder
        • Contains sodium             hydrogen carbonate. When heated it decomposes to make sodium carbonate and water and carbon dioxide gas is given off.          Sodium hydrogen carbonate?  sodium carbonate+ water+carbon dioxide
      • Additives
        • Antioxidants, material that stops food reacting with oxygen in the air. Food colouring, improve appearance in food. Flavour enhances, bring out flavour. Emulsifiers, help mix ingredients which would normally separate,
      • Emulsifiers
        • Molecules in a emulsifier have 2 ends. 1 like to be in water (hydrophilic) and the other end likes to be in oil (hydrophobic). Emulsifier join droplets together and keeps them mixed. The hydrophilic end of the water emulsifier molecule bonds to the polar water molecules. The hydrophobic end of emulsifier molecule bonds to non-polar oil molecules
    • Smells
      • Perfumes
        • Must smell nice, evaporate easily (travel up nose), non toxic, not irritate, not dissolve in water, not react with water (react with perspiration)
        • Esters
          • Used as synthetic perfumes. Made by reacting alcohol with organic acid. This produces an ester and water.
          • Perfumes are volatile (evaporate easily). Molecules in a drop of perfume are held together by a weak intermolecular forces of attraction. The molecules that escape have lots of energy and easily overcome the weak attraction to the other molecules in the liquid
        • Water doesn't dissolve nail varnish because the attraction between water molecules is stronger that the attraction between water molecules and the particles in nail varnish. Also the attraction between particles in nail varnish is stronger than the attraction between water molecules and particles in nail varnish
    • Paints
      • Special mixture of different material and that is called a colloid. In a colloid, fine solid particles are well dispersed with liquid particles but don't dissolve.
        • Mixture of Pigment(substance give paint colour), binding medium (oil sticks pigment to surface its being painted onto) Solvent (dissolves thick binding medium+makes it thinner+easier to coat surface
          • Paint coat surface with thin layer and solvent evaporates away as paint dries. Solvent in emulsion paint is water. In oil-based paints the pigment is dispersed in oil (binding medium).
            • Thermochromic pigments. Can be used in cups+kettles to warn when hot. Bath toys to show water is correct temperature for baby. Phosphorescent pigments glow in dark. To increase range of therochromuuc pigments they can be mixed with ordinary pigments in acrylic paints
            • Particle size of solids in colloid must be very small so they stay scattered throughout the mixture. If particles too big they would start to settle down to bottom.
              • Oil based paint dries in 2 stages. (1) Solvent evaporates away (2) Oil-binding medium reacts with oxygen in the air as it dries to form a hard layer. This is oxidation reaction

Comments

InNeedOfHelp

This was so helpful thank you!!!

zainiqbal

thanks

zainiqbal

but theres too much writing

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