C5

C5

1. Air

   • Dry air contains non metal elements such as: nitrogen oxygen and argon
   • Air also contains small amounts of non-metal compounds such as: CO2 and water vapour

2. Simple molecular substances

   • Have very low melting and boiling points
   • They are low because the intermolecular forces are weak
   • Very little energy is needed to overcome the forces
   • They have no free electrons moving around so they cant conduct electricity

3. Ionic crystals

   • The earths hydrosphere is all the water on earth
   • Hydrosphere is mostly water with some salts
   • When water evaporates dissolved salts from solid crystals
   • Salts are ionic compounds. Ions have either a positive or a negative charge and are arranged in a giant 3-D pattern called a lattice
   • The strong force of attraction between positively charged ions and negatively charged ions is called an ionic bond
   • Ionic compounds have high melting and boiling points
     • Because a large amount of energy is needed to overcome the strong intermolecular forces in the lattice
   • Ionic compounds do not conduct electricity when solid but do when they are melted or dissolved in water because the charged ions can move
   • Na+ and Cl- make NaCl; Mg2+ and Cl- make MgCl2
   • SO4 2- is a molecular ion

4. Testing for ions

   • Solutions of some ionic compounds make a precipitate of an insoluble compound when they mix.
   • Calcium Ca2+
     • White precipitate
   • Copper Cu2+
     • Light blue precipitate
   • Iron(II) Fe2+
     • Green precipitate
   • Iron(III) Fe3+
     • Red Brown precipitate
   • Zinc Zn2+
     • White precipitate
   • Negative carbonate ions are identified by adding dilute acid and looking for fizzing
     • Because CO2 is released
   • Negative chloride, bromide, iodide and sulfate ions are identified by adding dilute silver nitrate or dilute barium chloride and looking for precipitates

5. Metals minerals and ores

   • The litosphere is the rigid outer layer of the earth made up of the crust and the upper mantle
   • Minerals are solid with atoms or ions arranged in a regular arrangement or lattice
   • Silicon oxygen and aluminium are very abundant in the litosphere
   • Rocks contain metal minerals called ores
   • Extracting metals by heating their oxides with carbon is a redox reaction as both oxidation and reduction happen
   • Burning metals can only be used for elements less reactive than carbon

6. Diamond and Graphite

   • They are giant carbon covalent structures
   • Diamond
     • Bonds are very strong and need a large amount of energy to break them. This is why it has a high melting point and wont dissolve in water
     • There are no free particles in diamond so it doesnt conduct electricity
     • Each carbon atom has 4 bonds in a tetrahedral lattice
   • Graphite
     • Each carbon atom is strongly bonded to three others in sheets
     • The sheets are strong but there is a weak bond between the layers so they can slide over eachother
     • There are free moving electrons between the layers so it conducts electricity

7. Formula mass

   • The relative formula mass of a compound is the sum of the relative atomic masses of all the atoms in its formula
   • The gram formula mass of an element or compound is its relative atomic mass in grams
   • percentage of metal in mineral = total mass of metal atoms/gram formula mass

8. Electrolysis

   • Passing a current through an ionic compound when it is molten or dissolved in water
   • The compound being broken down is called the electrolyte - electrolytes break down as the current passes through them
   • It is used to extract more reactive metals because their oxides cannot be reduced by carbon
   • Metals form at the negative cathode because metals are positive ions
   • Negative ions such as chloride and oxide move to the positive anode

9. Metals

   • Are malleable - can be hammered into shape
   • The atoms are held by metalic bonds - atoms are arranged in a regular pattern or giant lattice
   • Metallic bonds are very strong and need a lot of energy to melt or reshape them
   • The metal ions lose their outer shell electrons to form positive ions in solid metals- this forms a sea of electrons that move around
   • The attraction between the + ions and sea of electrons is so high - so metals have high melting and boiling points
   • Metals conduct electricity as they have electrons that can move
   • In pure metals, all the atoms are the same size and can roll over each other - so metals are malleable
   • Environment
     • Lead mercury and cadmium are poisonous
     • Extracting and purifying metal ores needs a lot of energy
     • They have a very small yield
     • Some minerals contain sulphur and during extraction sulfur dioxide could be made