CHEM PAPER 1

• What charge is the nucleus?

  positive
• Relative mass of electron?

  0 (very small)
• Charge of electron?


  negative
• Relative mass of neutron?

  +1
• Charge of neutron?


  0
• Relative mass of proton?

  +1
• Charge of proton?


  +1
• What is the atomic number?

  number of protons
• What's the mass number?

  Total number of neutrons and protons
• What's the radius of a nucleus?


  1x10-14
• What are elements?


  Substance made up of atoms that all have the same number of protons in their nucleus
• What are isotopes?


  atoms with the same number of protons but different number of neutrons e.g Carbon 12 and 13
• What's the formula for relative atomic mass?

  Sum of (isotope abundance x isotope mass number)/sum of abundances of all isotopes.
• What is a compound?

  2 or more elements chemically combined
• How are compounds formed?


  Atoms sharing, giving or taking away electrons to form a full outer shell.
• What are mixtures?


  Two or more elements not chemically bonded together so they share properties of all the parts of the mixture.
• What does chromatography separate?

  Dyes in an ink
• Describe the method for chromatography?

  1) draw line in pencil near the bottom of a sheet of filter paper

  2) add a spot of ink to the line and place in a beaker of solvent e.g water

  3) the solvent depends on what's being tested as some compounds dissolve in water but sometimes they need solvents like ethanol.

  4) make sure ink isn't touching solvent

  5) place lid on top to avoid solvent evaporating

  6) the solvent should seep up the paper carrying the ink

  7) Each part of the dye will move at different rates, so will separate.

  8) if any of the dyes are insoluble, they will stay on the baseline.

  9) when the solvents nearly reached the top of the oater, take it out to dry.
• What are common mistakes made in chromatography?

  - start line should be in pencil, not ink as this will bleed

  - make sure lid is on to prevent evaporation

  - make sure the solvent is correct e.g water

  - make sure the solvent isn't above the start line as it will mix with the dyes and bleed.
• What are the 4 separation techniques?

  filtration, crystallisation, distillation, chromatography
• What does filtration separate?

  Insoluble solids from liquids
• Describe the method for filtration?

  -Use filter funnel and filter paper to filter the mixture
• What does evaporation and crystallisation separate?

  soluble solids from solutions
• Describe the method for evaporation?

  1) pour solution into an evaporating dish

  2) slowly heat the solution. The solvent will evaporate and the solution will keep getting more concentrated.

  3) Keep heating the evaporating dish until you are left with dry crystals.
• Describe the method for crystallisation?

  1) Pour out the solution into an evaporating dish and gently heat the solution. Some of the solvent will evaporate and the solution will get more concentrated.

  2) once some of the solvent has evaporated, or when you see crystals start to form (the point of crystallisation), remove the dish from the heat and leave it to cool.

  3) The salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution.

  4) Filter the crystals out of the solution and leave them in a warm place to dry.
• What does distillation separate?

  Liquids from a solution based on differences in boiling points
• Describe the method for distillation?

  1) The solution is heated. The part of the solution that has the lowest boiling point evaporates first.

  2) The vapour then cools and condenses and is collected.

  3) The rest of the solution is left behind in the flask.

  4) You can use simple distillation to get pure water from sea water.

  5) The problem with distillation is that its only easy to separate things with very different boiling points. Fractional distillation is used for things with similar boiling points.

  
• What does fractional distillation separate?

  More than two liquids with different (but more similar than when you use distillation) boiling points
• Describe the method of fractional distillation?

  1) Heat the mixture in a flask inside a fractionating column.

  2) The different liquids will have different boiling points so they will evaporate at different temperatures.

  3) The liquid with the lowest boiling point evaporates first, lower down in the column.

  4) When the first liquid has been collected, raise the temperature until the next one reaches the top.
• When and what was John Dalton's idea of the atom?

  19th C- atoms are solid spheres.
• What did JJ Thomson discover?

  He discovered the subatomic particle called the electron, which was small and negatively charged- plum pudding model. (Negative electrons were floating in a positively charged 'pudidng')
• What did Rutheford discover?

  He proved that the plum pudding model was wrong and discovered the mass of the atom was concentrated in the centre (nucleus) and most of the atom was empty space. through his alpha particle scattering experiment.
• Describe the alpha particle scattering experiment?

  1) A few particles were deflected by the nucleus showing it has a positive charge.

  2) Most particles passed through, showing the atom was mostly empty space.

  3) Some were sent backwards if fired directly at the nucleus showing it had a positive charge.
• What are ions?


  charged particles
• How are metal ions formed?

  They lose electrons from their outer shell to form positive ions (cations)
• How are non-metal ions formed?

  They gain electrons into their outer shell to form negative ions (anions)
• What is ionic bonding?


  - Metal and non-metal react together

  - The metal loses electrons to form a positive ion

  - The non-metal gains electrons to form a negative ion

  - oppositely charged ions have strong electrostatic forces of attraction.
• Properties of ionic compounds?

  - giant ionic lattice

  - strong electrostatic forces of attraction between oppositely charged ions

  - high melting/boiling points due to the many strong bonds between ions

  - can't conduct electricity when solid because the ions are held in place

  - when melted, the ions are free to move around and carry a charge.

  - some ionic compounds dissolve in water so the ions separate and are free to move and carry a charge.
• What is covalent bonding?


  When non-metal atoms bond together, sharing pairs of electrons to form strong covalent bonds
• Properties of covalent compounds/simple molecular substances?

  - low melting and boiling point due to weak intermolecular forces.

  - dont conduct electricity because they aren't charged, so there are no free electrons or ions.

  - soft and flexible.

  -most are gases/liquids at room temperature because of their low boiling/melting points.