C5
- Created by: emchown
- Created on: 10-03-15 16:38
View mindmap
- C5
- Atmosphere
- Layer of gas surrounding the earth
- Made up of elements: Nitrogen, Oxygen, Argon, Carbon Dioxide and Water Vapour
- Chemicals in the atmosphere consist of non-metal element and molecular compounds
- Molecules that make up the atmosphere are gases because they have very low melting points.
- Molecular compunds have strong covalent bonds between the atoms that make up the compound.
- Only weak forces of attraction between the small molecules
- Molecular compunds have strong covalent bonds between the atoms that make up the compound.
- Small amounts of energy are needed to break these forces
- Atoms within molecules (hydrogen) are connected by strong cobvalent bonds.
- Covalents bonds - electrons are shared between the nuclei of 2 atoms.
- Causes a strong, electrostatic attraction between nuclei and shared electrons
- Covalents bonds - electrons are shared between the nuclei of 2 atoms.
- Unlike ionic compunds, pure molecular compunds dont conduct electricity - molecules arent charged.
- Hydrosphere
- All the water on the Earth. The water contains dissolved compounds.
- Seawater is salty because it contains dissolved ionic compounds.
- eg Sodium Chloride; Sodium Sulfate; Potassium Bromide.
- The Water Molecule
- Good solvent for salts.
- Bent because electrons in covalent bond are nearer to oxygen atom than hydrogen atoms.
- A Polar Molecule
- Charges on atoms means forces between molecules are slightly stronger than any other.
- More energy needed to seperate
- Small charges help to dissolve ionic compounds as the water molecules attract ions.
- Lithosphere
- Rigid outer layer of Earth made from the crust and upper part of mantle
- Mixture of minerals (silicon dioxide)
- Abundant elements in it include Silicon, Oxygen and Aluminium
- Silicon Dioxide
- Giant Covalent structure
- Each silicon atom is covakently bonded to 4 oxygen atoms.
- Each oxgyen covalently bonded to 2 silicons.
- Strong, rigid sturcture.
- Doesnt conduct electricity - no ions or free electrons
- Does dissolve in water - no charge to attract water molecules
- High melting and boiling points
- Exists in different forms
- Quartz in Granite - main thing in Sandstone
- Amethyst - used as gemstone, cut and polished for jewellery.
- Used for Furnace Linings - high melting point, alot of energy to break bonds
- Carbon
- Giant Covalent Structure
- Diamond
- Large no. of covalent bonds - high melting and boiling point
- Each carbon atom covalently bonded to 4 others.
- Very strong, rigid, 3D structure - difficult to break down
- Insoluble - no charges to attract water molecules
- Doesnt conduct electricity - no ions or free electrons
- Used as Drill Tips - very hard and alot of energy needed to break covalent bonds
- Graphite
- Giant covalent structure
- Layered Structure
- Slide past eachother - soft and slippery
- Each carbon covalently bonded to 3 others
- Insoluble - strong bonds
- High melting and boiling points
- Can conduct electricity - electrons forming weak bonds between layers are free to move.
- Used in Pencils - soft, layers removed easy and stick to paper
- Identification of Ions
- Insoluble compounds will give precipitates - used to identify metal ions
- Oceans - dissolved calcium and carbonate ions form precipitate Calcium Carbonate (limestone)
- To identify a negtive ion, range of different test can be carried out
- Adding a reagent to unknown sample which react with ions to form an in soluble salt
- To identify a negtive ion, range of different test can be carried out
- Sulfate Ions
- Add barium chloride solution and dilute hydrochloric acid to sulfate solution
- A white precipitate of barium sulfate will be produced if a sulfate is present
- barium ion + sulfate ion = barium sulfate
- Chloride, Bromide and Iodide Ions
- Cream precipitate - silver bromide
- White precipitate - silver chloride
- To identify, add silver nitrate solution and nitric acid to suspected halide solution
- Yellow precipitate - silver iodide
- Most ionic compounds are soluble in water
- Insoluble compounds will give precipitates - used to identify metal ions
- Testing for Carbonates
- Acids
- Carbonates react with dilute acids to from carbon dioxide (and salt and water)
- eg. add calcium carbonate to dilute hydrochloric acid, carbonate will fizz and give off CO2
- calcium carbonate + hydrochloric acid = calcium chloride + carbon dioxide + water
- Thermal Decomposition
- Copper Carbonate and Zinc Carbonate heated - thermal decomposition reaction takes place
- Results in distinctive colour change which enables two compounds to be identified
- Heat copper carbonate (green) forms Copper Oxide (black)
- Heat Zinc Carbonate (white) forms Zinc Oxide (yellow at high temps.) Cools and returns whate.
- Acids
- Extracting Useful Materials (Lithosphere)
- Naturally occurring elements and compounds are called Minerals
- Ores are rocks that contain varying amounts of minerals of which metals and be extracted.
- Method of extraction depends on the metals postition on the reactivity series
- Metals above Carbon in the reactivity series are very reactive and have to be extracted by Electrolysis
- Metals below Carbon are extracted by reduction (heating with Carbon or Carbon Monoxide)
- All metals below hydrogen can be extracted using Hydrogen
- Gold and Platinum are unreactive so are obtained by physical processes (panning)
- Extraction by reduction with Carbon
- Zinc extracted from Zinc Oxide by heating with carbon
- Zinc oxide reduced because it loses oxygen
- Carbon is oxidised because it gains oxygen
- Zinc Oxide + Carbon = Zinc + Carbon Dioxide
- Metals and the Environment
- Life Cycle assessment of metal products must be carried out
- Making Mineral from Raw Materials
- Mining
- Rock wasted
- Scar on landscape
- Air pollution
- Noise pollution
- Processing
- Pollutants used by transportation
- Energy usage
- Extracting Metal
- Electrolysis uses more energy than reduction
- Mining
- Making Product from Mineral
- Energy usage in processing and transportation
- Use
- Transport
- Pollutants
- Running Product
- Energy Usage
- Transport
- Disposal
- Reuse
- No impact
- Recycle
- Less energy than initial manufacturing
- Throw Away
- Landfill sites remove habitats and are unsightly
- Reuse
- Extraction by Electrolysis
- Decomposition of an electrolyte (solution that conducts electricity) using electric current
- Ionic compounds will only conduct electricity when electrons are free to move (molten or dissolved in solution)
- Electrostatic forces between charged ions broken down
- Molten Lead Bromide
- Contains positive lead ions and negative bromide ions
- When current passed through the molten salt, postive lead ions sttracted towards negative electrode and negative bromide ions atrracted to positive electrode
- Lead is formed at negative and Bromine to positive
- When ions get to oppositely charged electrode, the are discharged.
- Bromide ions lose electrons to positive electrode - bromine atom
- Lead ions gain electrons from negative electrode - lead atom
- Aluminium Ore
- Too reactive to be extracted using carbon
- Aluminium oxide mixed with Cryolite to lower melting point
- Mixture melted
- Aluminium ion move towards negative electrode - aluminium formed
- Oxide ions attracted to positive electrode - oxygen formed
- Positive electrodes burn away quickly and have to be replaced frequently.
- Expensive process - large amounts of energy needed
- Positive electrode
- Al3+ + 3e- = Al
- Reduction
- Negative electrode
- 2O2- - 4e- = O2
- Oxidisation
- Properties of Metals
- Generally, metals are strong and malleable
- Metal crystalline structure - positively charged metal ions are held close together by a sea of electrons that are free to move
- Properties of a metal can be explained by its structure
- Force of attraction that keeps structure together is called a Metallic Bond
- Very Strong - metal ions closely packed together on a lattice structure
- High Melting Point - A lot of energy needed to break strong force of attraction
- Malleable - External forces cause layers of metal ions to move by sliding over other layers
- Conducts Electricity - Electrons free to move throughout structure. Electrical force applied, the electrons move along the metal in one direction
- Atmosphere
- Chloride, Bromide and Iodide Ions
- Cream precipitate - silver bromide
- White precipitate - silver chloride
- To identify, add silver nitrate solution and nitric acid to suspected halide solution
- Yellow precipitate - silver iodide
Comments
Report