chemistry paper 1

• atoms have a radius of 0.1nm
• nucleus contains the protons and neutrons - it has a positive charge because of the protons, thewhole mass of the atom is concentrated in the nucelus
• electrons are negativel charged and found in outer shells and cover a large amount of space
• protons: 1 relative mass, +1 relative charge
• neutrons: 1 relative mass, 0 charge
• electrons: small relative mass, -1 charge
• atomic number = number of protons
• mass number = sum of protons and neutrons
• atoms are neutral and have no overall charge - same no of protons and neutrons
• ions - atom with charge -> no of protons doesnt equal the no of electrons
• no of protons = no of electrons
• atomic no (bottom one) - no of protons
• mass number (top number) - total no of protons and neutrons
• elements - atoms with the same atomic number (same protons)
• isotope - different forms of the same elememt -> same no of protons, diff number of neutrons
• relative atomic mass = sum of(isotope abundance x isotope mass number)/ sum of all abundances
• compounds are made up of two or more elements chemically bonded together
• ionic bonding: when a compound formed by a metal and non metal consist of ions - the metal lose electrons to form positive ions and the non metal gain electrons to form negative ions - the opposite charges mean theyre strongly attracted to each other
• covalent bonds: when a molecule consists of only non metals - the atoms share pairs of electrons between them
• formulas show what atoms are in a compound e.g co2 has 1 carbon atom and 2 oxygen
• carbon dioxide - CO2
• ammonia - NH3
• water - H2O
• hydrogen chloride - hcl
• sodium chloride - NaCL
• carbon monoxide - CO
• calcium cholride - CaCl2
• left hand side - reactants

  right hand side - products
• mixtures - 2 or more elements or compounds mixed together, not chemcially and can be separated by physical methods like filtration and distillation
• properties of a mixture are just the properties of the separate parts
• paper chromatography:

  1. draw a line at the bottom of a filter paper using pencil (insoluble so it wont dissolve)
  2. add a spot of ink to the line
  3. place the sheet in a beaker of solvent (water or ethanol if it doesnt dissolve in water)
  4. make sure the ink isnt touching the solvent
  5. place a lid on top so it doesnt evaporate
  6. the solvent seeps up the paper and carries the ink with it
  7. each dye moves at different rates so they separate
  8. if the ink is insoluble (wont dissolve), they'll stay on the baseline
  9. leave the paper to dry
• mobile phase - the liquid that the solvent moves through in a chromatography
• stationary phase - when the ink is contained on the paper and does not move through it
• filtration separates insoluble solids from liquids
• how to separate soluble solids from solutions: evaporation and crystallisation
• evaporation:

  1. pour the solution into an evaporating dish
  2. slowly heat the solution - the solvent will evaporate and the solution will become more concentrated
  3. keep heating until dry crystals are left
• evaporation can only be used if the salt doesnt decompose
• crystallisation:

  1. pour the solution into an evaporating dish
  2. gently heat it - some of the solvent will evaporate and the solution will become more concentrated
  3. once the solvent has evaporated or when crystals start forming remove the dish from the heat and leave to cool
  4. the salt should start to form crystals as it becomes insoluble in the cold
  5. filter the crystals and leave them in a warm place to dry
• filtration and crystallisation is used to separate rock salt (mixture of salt and sand) since salt dissolves in water and sand doesnt:

  1. grind the mixture - make sure the salt crystals are small so it dissolves
  2. put the mixtrure in water to dissolve the salt
  3. filter the mixture to remove the sand, leaving salt water
  4. evaporate the salt solution to form dry crystals
• simple distillation separates a liquid from a solution: it can only be used when each part has very different bps - if the temp goes higher than the bp of the substances, they will mix again

  1. heat the solution - the part that has the lowest bp evaporates first
  2. the vapour is the cooled, condensed and collected