C5

C5

1. Atmosphere

   • Pure molecular compounds don't conduct electricity
     • Molecules aren't charged
   • Molecules that make up atmosphere are gases at 20°C
     • Low boiling points
     • Structure of molecules
       • Gases have small molecules with weak forces of attraction
         • Only small amounts of energy are needed to break forces
   • Consists of non-metal elements and non-metal molecular compounds
   • Atoms within molecules are connected by strong covalent bonds
     • Electrons are shared between atoms
     • Strong electrostatic attraction is created between a positive and a negative nucleus

2. Lithosphere

   • Made from crust and the part of mantle beneath it
   • Carbon in lithosphere
     • Diamond and graphite are formed from pure carbon
     • Graphite
       • Each carbon atom is covalently bonded to three other carbon atoms
       • Spare electrons can move between the layers so graphite conducts electricity
       • Arranged in sheets that slide easily over each other
     • Diamond
       • Each carbon atom is covalently bonded to four other carbon atoms
         • Very difficult to break
   • Silicon dioxide
     • Much of silicon and oxygen is present as silicon dioxide
     • Forms giant covalent structure - similar properties to diamonds
     • Properties
       • Gard
       • High melting point
       • Electrical insulator
       • Insoluble in water

3. Hydrosphere

   • Seawater is salty because it contains ionic compounds called salys
     • Sodium chloride is an ionic compound
       • Made from positive sodium ions and negative chloride ions
     • Ions are electrostatically attracted to each other
       • Form giants 3D crystal lattice with high melting and boiling points
   • If given table kg charges on ions, work out formulae for salts in the sea

4. Properties of ionic compounds

   • Ionic compounds have similar properties
     • High melting points
       • Ions are held together by strong forces of attraction in a lattice
     • Don't conduct electricity when SOLID
       • Ions are fixed in place and can't moce
     • Do conduct electricity when MOLTEN or DISSOLVED
       • Ions are free to move around
   • Many ionic compounds dissolve in water because water molecules are polar
     • Have a positive and negative end
     • A water molecule is attracted to an ion in the crystal lttice
       • An ion breaks away from the lattice
         • The ion moves freely through the water

5. Testing for ions

   • Precipitate ractions
     • In oceans, calcium ions (+) combine with carbonate ions (-)
       • Form insoluble ionic compound calcium carbonate
     • Use precipitation reactions to detect ions in aqueous solutions
     • Make predictions by interpreting information on solubility
       • Magnesium carbonate is insoluble
         • Mixing a solution with magnesium ions (magnesium chloride) with a solution with carbonate ions (sodium carbonate)
           • Results in precipitation of insoluble magnesium carbonaye
   • Testing for metal ions
     • Positive metal ions can be identified in solution by adding sodium hydroxide solution
       • Observe colour of precipitate
         • See page 43
     • Hydroxide ion has singular negative cahrge
       • Work out formula of metal hydroxide produced
         • Write a balanced ionic equation
           • See page 43
   • Many negative non-metal ions can be identified in solution
     • They will react with other aqueous ions to produce an insoluble precipitate
       • Examples on page 43

6. Extracting useful metals

   • ORES are rocks that contain varying amounts of minerals
     • Metals can be extracted from these
     • Sometimes large amounts or ores need to be mined to get a small amount of metal
       • Example - copper
   • Metals less reactive than carbon extracted from oxides by heating with carbon
     • Metal oxide is reduced, as it's lost oxygen
     • Carbon is oxidised as it has gained oxygen

7. Relative formula mass

   • Tells you the total mass of the atoms in a conpind
     • Add up relative atomic masses of elements
   • Metals mads
     • Write down firmula
       • Work out realise formula mass
         • Work out percentage mass of metal
           • Work out mass of metal

8. Electrolysis

   • Breaking down of an electrolyte using an electric current
   • Used to extract reactive metals from their ores
     • Too reactive it be extracted by heating with catbon
   • Ionic compounds conduct electricity when they're molten or dissolved in solution
     • Ions are free to move around through liquid
     • When an ionic compound melts, electrostatic forces between charged ions in crystal lattice are broken down - ions free
   • When a direct current is passed through a molten ionic cinpund
     • Positively charged ions are attracted towards the negative electrode
     • Negatively charged ions are attracted towards the positive charged electrodes
   • Molten lead bromide
     • Lead ions (+) go towards the negative electrode forming lead
     • Bromide ions (-) go towards positive electrode forming bromine
   • When electrons get to the opposite electrode, they DISCHARGED
     • The non-metal ion loses its electrons at the positive electrode to form a bromine ayom
       • Bromine atom the bonds with another to form a bromine milecule
     • Lead ions gain electrons to form a lead atom

9. Metals

   • Environmental impacts
     • Making material from raw materials
       • Rock wastsed
       • Leaves a scar on landscape
       • Air/noise pollution
       • Pollutants caused by transportation
       • Energy used
       • Electrolysis uses more energy than refuctuon
     • Manufacturing
       • Energy used in processing and transportation
     • Use
       • Pollutants caused by transportation
       • Energy usage
     • Disposal
       • Landfill sites remove wildlife habitats and are an eyesore
   • Properties
     • Giant structure of ions that are held together by strong forces of attraction
       • Called METALLIC BONDS
     • Strong - ions are closely packed in a lattice structure
     • High melting points - lot of energy needed to break metallic bonds
     • Malleable - beaten into shape or dented
       • Layers of ions can slide over each other
     • Conductors of electricity - electrons are free to move throughout the structure
       • When a voltage is applied, electrons move in one direction
     • Positively charged ions are held together by a sea of electrons