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Chemistry year 9 (Atomic structure (Discovery of the electrons led to the…
Chemistry year 9
Atomic structure
Discovery of the electrons led to the plum pudding model, JJ Thompson
The results from the alpha particle scattering led to the conclusion that the mass of an atom was concentration at the charge nucleus, Geiger and Marsden
Niels Bohr adapted the nuclear model by suggesting that the electrons orbit the nucleus
Rutherford, discovered protons
Chadwick, discovered neutrons
Name of particle and relative mass: Proton, 1. Neutron, 1. Electron, very small
Name of particle and charge: Proton, +1. Neutron, 0. Electron, -1
Solids, Liquids & Gases
Limitations of the simple model is that there are no forces between the spheres, that all particles are spheres and that the spheres are solid, they are actually empty
A mixture is not chemically combined
Pure elements and compounds melt and boil at a specific temperature
A formulation is a mixture that has been designed as a useful product. E.g medicine, cleaning agents and fertilisers
In paper chromatography a solvent moves through the paper carrying different compounds different distances, depending on their attraction for the paper and the solvent
Rf = distance moved by substance/distance moved by solvent
Chemistry of the atmosphere
80% nitrogen, 20% Oxygen, small proportions of various other gases
Intense volcanic activity, releasing gases that formed the atmosphere
Water vapour condensed to form oceans
Carbon dioxide was dissolved in the water an carbonates precipitated producing sediments
Algae and plants decreased the percentage of carbon dioxide and increased the percentage of oxygen through photosynthesis
Water
Potable water is water that is safe to drink
Potable water is produced by choosing an appropriate source of water, passing the water through filter beds and sterilising
Sterilising agents used for potable water include chlorine, ozone and ultraviolet light
Desalination can be done by distillation or by a processes that use membranes such as reverse osmosis
Sewage treatment
Screening - remove large solids, water passes through metal grid
Primary treatment - solid sediments sink to the bottom and and large paddle rods rotate and push the sludge towards the centre of the tank. Sludge is piped to storage tank
Secondary treatment - bacteria feeds on any remaining harmful microorganisms still present.
Final treatment - useful bacteria sinks to bottom and is recycled,
Periodic table
Mendeelev left gaps for elements that he thought had not been discovered and changed the order based on atomic weights
Group 0 elements are unrheactice, and do not easily form molecules as they are stable
Group 1, reactivity increases going down the group
Bonding
Ionic
Metals and non metals
Transfer of electrons
Compound
Held by strong electrostatic forces between oppositely charged ions
Metallic
Metals
Outer shell is delocalised. Held by strong electrostatic forces
Covalent
Non metals
Sharing electrons
Strong bonds
Greenhouse gases
Based on peer-reviewed evidence, scientists believe human activity will cause the temperature of the earth's atmosphere to increase
Carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product
Reactivity series
Potassium, Sodium, Calcium, Magnesium, Aluminium, Carbon, Zinc, Iron, Tin, lead, Hydrogen, Copper, Silver, Gold