Chemistry Revision  Structure and bonding  Structure and properties  How much?  Rates and energy  Salts and electrolysis

Columns = groups Group number = number of electrons in outer shell Rows = periods Row number = number of shells Periodic table

Type of sub-atomic particleRelative chargeMass Proton+11 Neutron01 ElectronNegligible Atomic structure

Each shell = different energy level Shell nearest nucleus = lowest energy level Energy needed to overcome attractive forces between protons and electrons Atomic structure

Very strong forces of attraction between positive and negative ions = ionic bond Look! Group 1 element Look! Group 7 element Ionic Bonding

Ionic bonds form a giant lattice structure Ionic Bonding

 Metals lose electrons  Non metals receive electrons  Elements become ions with a charge  Metals = + ion Non metal = - ion  High melting and boiling points – strong bonds  Solid at room temperature  Conduct electricity when melted or dissolved

Covalent Bonding (non metals) Simple molecules Giant structures

Covalent Bonding  Share electrons  Between non metals  No charge – don’t conduct electricity  Simple molecules have low melting and boiling points  Giant molecules have high melting and boiling points  Graphite and Diamond are examples

IonicSimple (covalent) Giant (covalent) Metallic Melting point  Boiling point  Electrical/ heat conductor Yes, when molten or in solution (aq) as allows ions to move No, due to no overall charge No – diamond Yes – graphite due to delocalised electrons Yes, due to delocalised electrons Strong electrostatic forces Strong covalent bonds, weak intermolecular forces Strong covalent bonds Structure and properties

Nanoscience  Small particles  Between 1 and 100 nanometres  Titanium oxides used in sunscreen  Can affect health  A spark can cause violent explosion

Polymers Thermo softening polymers  Melt easily when heated  Polymer chains easy to separate Thermosetting polymers  Strong covalent bonds  cross linking polymers  Don’t melt when heated

How much? Relative Atomic Mass (RAM)  Found on the periodic table  Tells you the number of protons and neutrons in an element  Always the bigger number of the 2

How much? Relative Formula Mass (RFM) or Relative Molecular Mass  Works out the mass of a compound  Find the RAM for each element  Add all the RAM numbers together  If there is a number (H 2 SO 4 ) multiply the RAM by that number  (Hx2) + S + (Ox4)

How much? Percentage Mass of an element  Calculate the RAM and RFM of the compound % mass = RAM (x number of atoms) x 100 RFM  If the number is larger than 100 check it

How much? Percentage Yield  Yield is how much is made  Percentage yield calculates how much is made compared to maximum amount  Rarely 100% because not all reactants react and some product gets left behind % Yield = amount of product produced x 100 Maximum amount of product possible

How much?

Gas Chromatography  Separates compounds  Used to identify unknown substances  Sample mixture is vaporised  Compounds with weaker attractions leave the column quicker  Times are recorded are compared to known substances

How much? Mass Spectrometer  Uses the separated compounds from Gas chromatography  Can identify elements  Identifies very small amounts of substances

Rates and energy Collision theory Chemical reactions only occur when reacting particles collide with each other with sufficient energy. The minimum amount of energy is called the activation energy Measure the rate of reaction by:  Gas produced  Mass decrease

Rates and energy Surface area  Larger surface area  Increases the number of collisions  More particles can react  Powder has large surface compared to lumps

Temperature  Higher temperature – more collisions  Heat gives particles kinetic energy  Particles move more quickly  Therefore collide more often in less time Rates and energy

Concentration/Pressure  Higher concentration/pressure – more particles  Less space so number of collisions increases Rates and energy

Catalyst  Speeds up the rate of chemical reaction  Not used up in the reaction  Reusable  Don’t need to have high temperatures which are expensive  Transition metals typically used Rates and energy

Exothermic  Give energy out to surroundings  Measure by increase of temperature Examples  Hand warmers  Self heating can (calcium oxide + water  Calcium hydroxide) Endothermic  Take in energy from surroundings  Measure by decrease of temperature Examples  Cold packs (ammonium nitrate + water)

Hydrated Anhydrous copper sulphate copper sulphate + water Exothermic reaction Endothermic reaction Rates and energy

Salts and electrolysis Acids  H+ ions  pH 0-6  HCl, H 2 SO 4, HNO 3 Alkalis  OH- ions  pH 8-14  NaOH  Alkalis = soluble bases

AcidFormulaSaltExample HydrochloricHClChlorideSodium chloride SulphuricH 2 SO 4 SulphateCopper sulphate NitricHNO 3 NitratePotassium nitrate Salts and electrolysis

1.acid + alkalisalt + water 2.acid + metalsalt + hydrogen 3.acid + metal oxide salt + water 4.acid + carbonate salt + carbon dioxide + water    

Salts and electrolysis Insoluble salt – from precipitation reaction (2 liquids react and make a solid) Method: 1.Mix the 2 chemicals (potassium Iodide and Lead Iodide) 2.Filter the precipitate 3.Wash the precipitate and leave to dry

Salts and electrolysis Neutralisation (pH 7) = acid and alkali Method: 1.Add universal indicator to your acid 2.Slowly add the alkali until the colour turns green (neutral) 3.Record the amount used and repeat without indicator 4.Pour the solution into evaporating basin 5.Heat using the Bunsen burner

Electrolysis  splitting up using electricity  Ionic compounds  Molten/liquid  Opposites attract  Metal  negative electrode  Non metal  positive electrode  OIL RIG – oxidation in loss, reduction is gain Non-metal ion Metal ion Salts and electrolysis

Extract aluminium from bauxite ore Use cryolite to lower melting point from 2050 to C

At anode2Cl - (aq)  Cl 2 (g) + 2e - At cathode2H + (aq) + 2e -  H 2 (g) In solutionNa + and OH - Salts and electrolysis