chemistry 1

• what are isotopes? 


  different forms of the same element that have the same number of protons but a different number of neutrons
• what is the equation for relative atomic mass? 


  sum of (isotope abundance (amount) x isotope mass number) / sum of abundances of all the isotopes
• compounds and mixtures, which is easily seperated?


  Mixtures
• what is the difference between a mixture and a compound?


  mixtures do not have chemical bonds
• name seperation techniques?


  Extraction, distillation, chromatography, filtration, evaporatio and crystallisation
• what is simple distillation used for? 


  separating a liquid from a solution
• what is the simple distillation process?


  1 heat the solution

  the part with the lowest boiling point with evaporate first

  2 the vapour is then cooled and condensed back into a liquid
• what is fractional distillation used for? 


  separating liquid from a solution when they both have similar boiling points
• what is the fractional distillation process?


  1 solution heated on a flask and the lowest boiling point rises first up the fractionating column

  the second liquid may begin to ev but the top of the column is cool so it will condense and run back down
• who discovered the plum pudding model?


  J.J. Thomson
• who discovered the plum pudding model was wrong and what did he discover?

  rutherford and the nucleus is positively charged
• who discovered electrons and the model today? 


  John Bohr
• how was the periodic table organised in the 1800s?


  by atomic weight
• who changed the periodic table?

  mendeleev
• why did mendeleev leave gaps in the periodic table?


  Predicted missing elements.
• as you go down group 1, what happenns?


  Reactivity increases

  Lower melting and boiling points
• what are the elements in group 1?


  soft reactive metals
• what is the name of group 1 elements? 


  alkali metals
• what are group 7 elements called? 


  halogens
• what happens has you go down group 7?


  reactivity decreases

  higher melting and boiling points
• what are group 0 elements called? 


  noble gases
• what happens has you go down group 0?


  increased boiling point