Chemistry Topic 2

• What is a compound?

  2 or more elements chemically combined
• what is chromotography?


  a method to seperate the different dyes in inks.

  it is a method of seperating substances in a mixture
• what is filteration?


  filteration seperates insoluble solids from liquds
• what is a mixture?

  A combination of two or more substances that are not chemically combined
• State the steps for crystalisation

  1) pour solution into an evaporting dish and gently heat the solution, some solvent will evaporate and the solution will get more concentrated.

  2)once solvent evaporated crystals form

  3)filter the crystals out the soutluion
• Define distillation?


  seperating a liqud from a solution
• state the steps for filteration

  1)pour solutions into an evaporating dish

  2)heat the solution, then the solvent will evaporate and the solution will get more concentrated.

  3)keep heating the dish untill all you have left are crystals
• whats the problem with distillation?

  only use it to seperate things with different boiling points.
• what is fractional distillation?


  used to seperate a mixture of liquds.
• Who described the atom as a 'solid sphere'?

  John dalton in the 19th century.
• who found electrons?


  jj thompson in 1897
• What did jj thompsons discovery of the electrons lead too?

  plum pudding model
• what is the plum pudding model?

  It states that atoms are a ball of positive charge, with negative electrons embedded in it
• What was the scattering experiment by ernest ruthford?

  he fired alpha particles at an extremely thin sheet of gold.
• what did the scattering experiment prove?

  particles bounced back= posiitve charge in the atom(protons)

  particles went straight through= empty space

  some deflected= great mass in the middle (nucleus)
• Who adapted the nuclear model?

  Niels Bohr
• How did Niels Bohr adapt the nuclear model?

  Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances.
• what did james chadwick find?

  neutron through his experimental work
• What are the simiarties of the NM and the PPM

  similarties:

  both contain electrons/a positive charge

  differences:

  PPM has a weakly positive atom

  NM has a triny strong positive nucles

  PPM has embeded electrons and NM has electrons orbiting the nucleus in shells.
• what is the size of an atom?

  10^-10 m
• what is the radius of an atom?

  1 x 10^-10 metres
• In the early 1800s how were elements arranged in the periodic table?

  atomic weights,

  physics and chemical properties
• What was mendeleevs table like?

  - left gaps and predicted new elements.

  -arranged in increasing atomic weights
• How are elemnts in the modern periodic table arranged in?

  increasing atomic number

  non-metals to the left

  metals to the rights
• coloums are?


  elements with similar properties
• vertical colomus are?


  groups, the group number tells you how many electrons are in the outer shell
• the rows are?


  periods
• Properties of metals


  Malleable, Ductile and Good Conductors of Heat and Electricity, high mp and bp, strong, shiny
• properties of non-metals


  Not malleable or ductile, not shiny, poor conductors of heat and electricity, brittle, low density,
• Properties of transition metals

  dense, strong, shiny, often coloured, good catalysts
• What are the group 1 metals called?

  alkali metals
• Properties of group 1 metals?

  soft

  low density

  lithum sodium potassium are less dense then water.

  one electron in outer shell
• What are the trends of group 1 metals as you go down?

  1) increases reactivity, as the outer electron is more easily lost because the attraction between the nuclus and electron decreases.

  2) low mp and bp

  3) high relative atomic mass
• How do group 1 metals react with water?

  react vigourusly and produce hydrogen gas and metal hydroxides.

  example:

  sodium+water----> sodium hyrdroxide+hydrogen
• How do group 1 metals react with chlorine?

  react vigoursly and from white metal chloride salts.

  sodium+chlorine---->sodium chloride
• How do group 1 metals react with oxygen?

  react with oxygen to form metal oxides.
• What are group 7 elements called?

  Halogens (non-metals)
• properties of fluorine


  A very reactive, poisonous yellow gas
• properties of chlorine


  failry reactive,poisonous, pale green gas
• properties of bromine?


  it's a dense, volatile red-brown liquid