C5
- Created by: Jessie leitch
- Created on: 19-03-16 11:54
Molecules in the air
Dry air contains non-metal elements eg. nitrogen, oxygen argon. Air also contains small amounts of non-metal compounds eg. carbon dioxide and water vapour. The atoms in thre molecules are held together with covalent bonds because covalent bonds occur between non-metals:
Covalent bonds form when atoms share a pair of electrons to gain a full outer shell. The atoms are held together because there is electrostatic attraction between the nuclei of the atoms and the electrons shared between them. Eg. In water hydrogen atoms and a oxygen atom share electrons to gain full outer shells.
For most covalent molecules, the forces between molecules are weak but the forces within the molecules (covalent bonds) are strong. Therefore, they are often gases due to there low boiling/ melting points as they are small molecule and little force is needed to overcome the forces between molecules. They don't conduct electricity as molecules are charged.
Most non-metal elements and most compounds between non-metal elements are molecular
Ionic cystals
The hydrosphere is mostly water with some dissolved compounds called salts.
These salts contain ions arranged in a regular lattice. Ionic bonds are formed because there is a metal and a non metal. The strong ionic bonds mean they have a high boiling/ melting points. They dont conduct electricity unless dissolved or molten because ions are fixed and cannot move.
In the formula for an ionic compound the number of positive charges balance the negative charges eg.Mg2+ and Cl- make MgCl2. some ions, eg. sulphate, contain groups of atoms. This is called a molecular ion.
Solutions of some ionic compounds may form a percipitate. Percipitates form when an insoluble solid is made in the reaction. For example most metal hydroxides are insolable as is silver chloride from the reaction of silver ions and chloridre ions
Ionic equations with state symbols show what happens what percipitates form:
Cu2+ (aq) + 2OH- (aq) --> Cu(OH)2 (s)
Giant molecules and metals
The lithosphere is made of rocks and minerals. Minerals are solids with atoms or ions arranged in a lattice. The most abundant elements in the lithosphere are
- oxygen
- silicon (mostly as silicon dioxide another giant covalent compound)
- aliminium
Rocks that contain metal minerals are called ores. Some ores containe metal oxides.
Diamond and graphite are minerals, both of which are composed of carbon atoms. Diamonds are very hard, have high melting and boiling points, do not conduct electricity and are insolubal because of strong ionic bonds
Like diamond, graphite has a giant molecular structure. However, graphite contains layers of carbon atoms. The layers slide over each other easily because there are only weak forces between them, making graphite slippery. Graphite contains electrons which can inderpendantly move through the graphite, carrying charge from place to place and allowing graphite to conduct electricity.
Water and salts in the hydrosphere
Electostatic attraction between partial charges produce inter molecular forces produce inter molecular charges. These are no as strong as ionic or covalent bonds
Water is a good solvent for salt
solvent + solute --> solution
water + salt --> solution
salts dissolve as oxygen has a slight negative charge so it pulls out the sodium from the sodium chloride one at a time
Extracting metals from ores
Methods of extraction:
- Some elements are found naturally as metals because they are so unreactive eg. gold
- Some elements are extracted by reduction as carbon is more reactive so displaces the metal. The reduction is done in a blast furnace. There is equal contact between the metal oxide and the charcol. Oxygen released from the iron oxide will react with the carbon to create carbon dioxide. The metal is left to cool and solidify.
- Some elements are extracted by electrolysis when they are more reactive than carbon eg. aliminium. Eletrolysis is the splitting of currents using an electrical current.
Bauxite= alliminium ore. Sodium hydroxide is added to the bauxite to remove any impuritities. The bauxite is made molten by using heat to break the ionic bonds. The aliminium goes to the negative electrode because it is positive and it gains 3 electrons in an oxidation reaction. The oxygen goes to the negative electrode because it is positive and looses 2 electrons in a reduction reaction. It them reacts with another oxygen to become a diatomic gas
- Al3+ + 3e- --> Al
- O2- + O + e- O + O --> O2
Issues with extracting metals
Is there a good supply of ore?
How can the ore be reduced? Reduction, electrolysis
Impact on the environment? CO2 is produced, noise pollution, dust production , waste rock, leaves large holes left in the ground, caves may cave in.
Energy cost? electricity is need, too expensive
Production? waste may contain traces of toxic materiels such as lead and mercury
Calculating molecular mass
Calculate total mass of metal 52 x 2 = 104
Calculate total mass of mineral 104 + 56 + (16 x 4) = 224
Calculate percent 104/224 x 100 = 46%
Turn percent into grams 100grams = 46grams
Metals
Metallic bonds occur between two metals. They are strong but weaker than covalent and ionic. All the ions are positive
The attraction between the positive charge on the metal atoms and negative charges are able to move and so can conduct electricty. It also means that metal are malleable as positive ions can move into space and slide past each other forming new shapes
The atom gives up an electron for a full outer shell. the electrons are attracted to the ions so they are held together. Ions are not repelled as electrons between.
The life of metals
- mining the ore
- ore is crushed to increase the surface area
- purifying of the metal
- extracting the mineral using electrolysis
- metal ingot
- shaping the metal
- recycle scrap metal
- metal ingot
- manufacturing products from the metals
- recycle scrap metal
- metal ingot
- end of useful life
- seperate and recycle waste metal
- metal ingot
- rubbish to waste tip
Related discussions on The Student Room
- Punishment »
- How do I catch up on GCSE chemistry? »
- CyberStart Game 2020/2021 (CyberDiscovery UK) »
- Isolation discipline »
- Froggatt Endcliffe »
- UCAS Personal Statement »
- Cyberstart Game level 5 »
- aiming for all 9s »
- AQA A-level Computer Science Paper 2 (7517/2) - 19th June 2023 [Exam Chat] »
- Revision Struggles?! Join the 2023 TSR All Day Revision Thread! »
Comments
No comments have yet been made