Chemistry Unit 1 Part 1

Chemistry Unit 1 Part 1

1. Atoms and elements

   • Inside atoms
     • Proton = +1
     • Neutron = 0
     • Electron = -1
     • Mass number
     • Atomic no. (number of protons and electrons)
     • Group 1 elements only have 1 electron in their highest level
       • Potassium and sodium
     • Group 0 have full outer shells so they are very stable and unreactive
       • Neon and argon
   • Inside compounds
     • Made up of two or more elects , strongly joined together
     • Ionic bonding
       • Metal and non-metal
       • Metal transfers one electron to the non metal
       • Each atom has a full outer shell
       • Charged atoms = ions
       • Forces of attraction (negative and positive) are ionic bonds
     • Covalent bonding
       • Non-metal and non-metal
       • Atoms share electrons to form covalent bonds
   • An atom is the smallest particles of a chemical elects that can exist
   • An element is made of just one sort of atom
   • All the elements are listed in the periodic table
     • The vertical columns are called groups
       • The elements in a group have similar properties
     • Group 1 are silvered-coloured metals that react with water
     • Elements in group 0 are gases at room temperature and don't usually react with other substances
     • Elements on the left of the stepped line are metals and on the right are non-metal

2. Chemical reactions

   • Chemical equations

3. Limestone

   • The lime cycle
     • Calcium carbonate (limestone)
       • Heat
         • Carbon dioxide gas
         • Calcium oxide
           • Add a few drops of water
             • Solid calcium hydroxide
               • Add more water and filter
                 • Calcium hydroxide solution (limewater)
                   • Add carbon dioxide
   • Products from limestone
     • Crushed into small lumps to make aggregate
     • Calcium oxide and calcium hydroxide both form alkaline solutions with water
       • Neutralise acidity in lakes/oils and acidic waste gases produces by burning coal in power stations
     • Cement
       • Crush limestone rock into small pieces
         • Add powdered clay and heat the mixture to 1450 degrees in a rotating kiln
           • Thermal decomposition ( calcium oxide (quicklime) and carbon dioxide)
           • Add a little calcium sulfate powder
     • Concrete
       • Mix sand , cement , aggregate and water
     • Mortar
       • Mixing a thick paste from cement , sand and water
     • Decomposing metal carbonates
       • Pattern
         • Metals low in the reactivity series = small amounts of energy to break them down
           • High reactive metals = lots of energy to decompose them
             • Very reactive metals = don't decompose at bunsen burner temperatures
               • Potassium carbonate
             • Sodium carbonate
           • Copper carbonate
       • copper carbonate (green) --> copper oxide (black) + carbon dioxide
   • Quarries
     • Benefits
       • Provides jobs where they may be scarce
         • Quarries produce materials worth billions and this contributes to the countries economy
     • Problems
       • In attractive areas it can damage tourism
         • Transportation creates traffic
           • It takes up land space which is then unavailable for farming and recreation
   • Formed from the shells of creates that lived in shallow seas
   • Raw material for the production of materials including cement , mortar and glass
   • Attractive , durable and strong
   • Cut into blocks
   • The surface of limestone can be damaged by acid rain
     • calcium carbonate + sulphuric acid --> calcium sulfate + carbon dioxide + water

4. Magnificent metals

   • Stunning steel
     • Iron
       • Cast
         • Re-melting blast furnace iron and adding scrap stewl makes cast iron
         • Has a high stretch in compression - used for cannons and cooking pots
       • Pure
         • Remove impurities
         • Regular arrangement of atoms so they slide over each other making it soft and easy to bend into shapes
     • Carbon steels
       • Low % of carbon - less than 0.3%
         • Easy to make into shapes
         • Car body panels and food cans
       • High % of carbon - 0.6 - 1 %
         • Hard and strong
     • Stainless steel
       • Iron and steel rust when they react with water or oxygen in the air = corrosion
         • Weakens structures - cost money and lives
       • Stainless steel doesn't rust - corrosion resistant
       • Contains chromium atoms
       • Cutlery , surgical instruments and kitchen sinks
     • Mainly iron mixed with certain amounts of carbon
     • Alloy (mixture of a metal with one or more elements ) - layers of atoms so it can't slide easily
   • Copper
     • Phytomining
       • Plant certain plants on low-grade copper ores
         • Plants absorb the copper compounds
           • Burning the plants produces ash that is rich in copper compounds
     • Bioleaching
       • Some bacteria can obtain their nutrients and energy from copper compounds in copper ores
         • The bacteria produce solutions of copper compounds
           • Chemical reactions or electrolyse extract the copper
             • Very slow process
     • Uses
       • Pipes as it bends easily
       • Wires as it conducts electricity well
       • Coins when mixed with nickel
       • Bottom of plans as it conducts heat well
     • Obtaining pure copper
       • 1. Dig ore from an open cast mine
         • 2. Concentrate the ore to separate copper minerals from the waste rock of the ore
           • 3. Make a solution of copper compounds from the ore and use electrolysis
           • 3.Heat the concentrated ore in a furnace where chemical reactions remove other elements (smelting)
           • 4. Electrolysis
             • Negative electrode is made of pure copper
               • Impure copper forms the positive electrode
                 • During electrolysis , positive copper ions move to the negative electrode
                   • Waste material falls to the bottom of the beaker and it damages the environment
     • Can also be obtained from solutions of copper salts by adding scrap iron to the solutions
       • iron + copper sulfate --> iron sulfate + copper
   • Titanium and aluminium
     • Titanium is extracted using a multi-step process which uses lots of energy so is expensive
       • Low density
       • Resists corrosion
       • Transition metal
       • Aeroplanes , artificial hips and bone pins or oil rigs at sea
     • Aluminium is extracted by electrolysis , which uses a lot of electrical energy which is expensive
       • Low density
       • Corrosion resistant
       • Aeroplanes , overhead power cables , drink cans and cooking foil
     • Expensive because they can't be extracted easily by heating their ores with carbon
       • Aluminium is above carbon in the reactivity series , its atoms are joined very strongly to oxygen atoms in bauxite
         • If you heat titanium oxide with carbon you make it titanium carbide and this is a brittle metal
     • Recycling - creating new cans only uses 10% of the energy and less pollution is created
   • Transition metals
     • Central block of the periodic table
     • Shiny surface weh freshly cut
     • Can be bent or hammered without cracking
     • Good conductors of heat and electricity
   • Iron
     • Extracting ores
       • 1. Put the iron ore in a hot blast furnace with coke (carbon)
         • 2. Oxygen is removed from the iron oxide in reduction reactions. The products are iron and carbon dioxide
       • If below carbon they are also extracted by heating their oxides with carbon
     • Too reactive to exist on its own
       • Joined to other elements in naturally occurring compounds called minerals (mixed with sand or rock) = ORES
   • Gold
     • Found as a metal on its own as it is unreactive
       • Hardly ever joins to other elements to form compounds
     • In its NATIVE STATE

5. Making crude oil useful

   • Looking into oil
     • Alkanes
       • Longer chain alkanes are more viscous because their molecules get more tangled (don't pour easily)
         • The smaller the molecules , the lower the boiling point
           • Alkanes with small molecules catch fire more easily
   • Burning dilemmas
     • Carbon dioxide
       • Formed by the complete combustion of hydrocarbons
       • Global warming
         • Impacts
           • Climate change
             • Weather patterns change
               • Extreme weather events
             • Some species will die
             • Some species such as the mosquito may spread over wider areas
           • Melting ice caps
             • Sea levels rise
             • Increased flooding
         • 1. Radiation from the Sun enters the Earths atmosphere and reaches the Earth surface
           • 2. The radiation warms up the Earths surface
             • 3. The Earths surface radiates heat energy, Some of the heat energy goes directly into space whilst some is absorbed by carbon dioxide gas in the atmosphere
               • 4. The atmosphere radiates some of its heat energy back towards the Earth and the Earths surface gets hotter
         • Solutions
           • Use less or alternate fuels
     • Particulates
       • Burning diesel produces tiny pieces of solid
       • Causes global dimming
         • In the atmosphere , particulates reflect sunlight back into space - so less reaches the earths surface
     • Acid rain
       • When coal burns it produces sulfur dioxide gas , carbon dioxide and water
       • If sulfur dioxide goes into the air it dissolves in water in clouds and makes acid rain
       • Oxides of nitrogen such as nitrogen dioxide , are formed when hydrocarbon fuels burn at high temperatures in car engine
       • Makes lakes more acidic
         • Damages trees (dissolves soil nutrients and washes them away , also damages the protective waxy coating of leaves - can no longer produce food)
           • Damages limestone buildings
     • Carbon monoxide
       • Poisonous
       • Incomplete combustion
   • Separating oil fraction
     • 1. Crude oil is evaporated at 450 degrees and enters the fractional column as a gas
       • 2. The fractional column has a temperature gradient ( it is hotter at the bottom and cooler at the top)
         • 3. Once a fraction has cooled to below its boiling point (turns from a gas into a liquid) it is removed
           • 4. Fractions with higher boiling points are removed at the bottom of the column and vide versa
   • Contains many hydrocarbons (compounds of hydrogen and carbon)
   • Mixture , so it is not chemically joined and each hydrocarbon has its own properties

6. Biofuels

   • Plant oil fuels are renewable but they produce carbon dioxide on burning
   • Problems
     • Deforestation to make room for crops damages biodiversity
       • Emissions of oxides of nitrogen cause asthma and lung disease
         • Produces lots carbon dioxide
           • Evicted people from land
             • Land could be used to grow food
   • Benefits
     • Provides jobs
       • Generate renewable sources for electricity
         • Carbon neutral

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