fifths (paper 2)

• solubility is the maximum mass of a solute that dissolves in 100g of solvent
• moles = concentration x volume
• amount (mol) = volume (dm^3) / 24
• 1dm^3 = 1000cm^3
• 1. Add some alkali and 2-3 drops of indicator to a conical flask using a pipette and a pipette filler.
  2. Fill the burette with acid- do this below eye level.
  3. Using the burette, add the acid to the alkali a bit at a time.
  4. The indicator changes colour when all the acid has been neutralised.
  5. Record the volume of acid used to neutralise the alkali.
  6. Repeat this process a few times to obtain more reliable results.
• metallic bonding = electrostatic attraction between positive ions and a sea of delocalised electrons
• metallic structure = regular lattice arrangement of positive ions held together by delocalised electrons
• metals are good conductors because they have delocalised electrons which are free to move
• metals are malleable (can be hammered into shape) because they have layers of ions that can slide over each other
• covalent compounds do not conduct electricity because there are no charged particles that are free to move
• ionic compounds only conduct electrically when molten or in solution as the ions are free to move
• negative ions are called anions, and positive ions are called cations
• electrolysis = the breaking down of a substance caused by passing an electric current through an ionic compound which is molten or in solution
• Electrolysis of molten lead bromide:

  • solid lead bromide is heated and becomes molten (ions are free to move)
  • electrodes attached to a power source are placed in the molten lead bromide
  • anode = positively charged
  • cathode = negatively charged
  • at the anode a brown has is given off (bromine gas)
  • at the cathode a shiny substance is formed (molten lead)
• as you go down group 1, the outer electron lost from the metal is further from the nucleus, therefore the electron is less attracted by the nucleus and therefore more easily lost
• the higher we go up in group 7, the more reactive the element
• most metals are found in the Earth's crust combined with other elements. such compounds are found in rocks called ore
• a few very unreactive metals, such as gold, are found native which means they are found in the Earth's crust as the uncombined element
• if an ore contains a metal which is below carbon in the reactivity series then the metal is extracted by reaction with carbon in a displacement reaction
• if the ore contains a metal which is above carbon in the reactivity series then electrolysis is used to extract the metal
• uses of aluminium: cans, power cables, pots and pans
• properties of aluminium: low density, resists corrosion, conducts electricity, strong, good conductor of heat
• uses of copper: electrical wires, pots and pans, water pipes
• properties of copper: good conductor of electricity, ductile, unreactive, malleable
• uses of iron: buildings, saucepans
• properties of iron: strong, conducts heat, high melting point
• uses of mild steel: nails
• uses of high-carbon steel: cutting tools
• uses of stainless steel: kitchen sinks
• properties of mild steel: strong material that is malleable and rusts easily
• properties of high-carbon steel: harder than mild, more brittle
• properties of stainless steel: forms a strong protective oxide layer - very resistant to corrosion
• what is an alloy?

  a mixture of a metal with other metals or carbon e.g. brass (copper + zinc)
• why are alloys harder than pure metals

  in alloys, different elements have slightly different sized atoms - which breaks up the regular lattice arrangement - making it difficult for layers of ions to slide over each other