CHEM PAPER 1 - common questions

• Give 3 physical properties of the alkali metals

  - soft

  - low melting point

  - low density
• describe what you would see when a small piece of sodium was added to water

  - fizzes/bubbles

  - floats

  - melts into a ball
• how would the reaction be different when a small piece of potassium was added to water?

  - fizz more

  - moves more

  - lilac flame
• write a word and symbol equation for the reaction of sodium with water

  sodium + water -> sodium hydroxide + hydrogen

  2Na + 2H2O -> H2

  
• explain how the reactivity changes going down group 1

  - going down they are more reactive

  - the atoms are larger

  - the outer electron is less attracted to the nucleus

  - the outer electron is lost more easily
• give three differences in the physical properties of transition elements compared to group 1 elements

  - harder

  - higher density

  - higher melting point
• give two ways in which the chemical properties of transition metals are different to alkali metals

  - more reactive

  - form ions with different charges
• how were the first periodic tables arranged?

  by atomic weight - protons had not been discovered
• give two problems with the early periodic tables

  - some boxes had two elements

  - metals and non-metals in the same group
• how did Mendeleev improve the table?

  - left gaps for undiscovered elements

  - switched the order of some elements (iodine and tellurium)
• why was it an improvement?

  so they were in groups with similar properties
• why did other chemists later accept his versions?

  - he had predicted the properties of undiscovered elements

  - when they were discovered, they matched his predictions
• proton mass


  1
• neutron mass


  1
• Electron mass


  1/2000
• proton charge


  +1
• neutron charge


  0
• Electron charge


  -1
• explain why all atoms are neutral?

  same number of positive protons and negative electrons
• what are ions ?

  charged particles
• what are isotopes?


  atoms with the same number of protons but different number of neutrons
• the radii of isotopes are both 0.128 nm. suggest why the two isotopes have the same atomic radius?

  each has the same number of protons and electrons, so outer electrons have same attraction the the nucleus
• give two physical properties of the halogens

  - low melting point and boiling point

  - poisonous

  - smelly
• explain why the boiling point increases going down group 7

  - molecules are bigger down the group

  - the atoms are larger

  - the outer electron is less attracted to the nucleus

  - it is harder to gain an electron
• what would be made and what would you observe when chlorine is added to a solution of sodium iodide?

  - brown iodine is made

  - sodium iodine + chlorine -> sodium chloride + iodine
• Explain why the noble gases are unreactive

  full outer shell of electrons
• why are noble gases in group 0 rather than group 8?

  - have full outer shells

  - most have 8 electrons in outer shell

  - but helium only has 2
• describe the plum pudding model of atoms

  a ball of positive charge with electrons embedded
• in the scattering experiment, what was fired at a thin layer of atoms?

  positive alpha particles
• give two observations and two conclusions from the scattering experiment

  - most particles went through so the atom is mostly empty space

  - some were deflected so the atom has a small positive nucleus
• describe what happens when potassium reacts with oxygen to produce potassium oxide

  - two potassium atoms each lose one electron

  - one oxygen atom gains two electrons to form K+ AND O2- ions with full outer shells of outer electrons
• explain why potassium oxide has a high melting point

  - giant ionic lattice

  - strong electrostatic attraction between oppositely charged ions in all direction that need lots of energy to break
• explain the electrical conductivity of potassium oxide

  conducts when molten or dissolved as the ions are free to move and carry a charge
• explain why ammonia has a low boiling point

  it is a simple covalent molecule with weak intermolecular forces that need little energy to break
• explain the electrical conductivity of ammonia

  does not conduct as it has no delocalised electrons or ions
• give two limitations of the particles model

  - not 3D

  - doesn't show the bonds

  - all particles are circles
• give 4 characteristics of a good model of a molecule

  - 3D

  - shows bonds

  - shows type and relative size of atoms
• describe the shape of fullerenes

  hollow spheres with hexagonal rings of carbon atoms

  
• why are fullerene used to transport drugs in the body?

  drugs are carried inside the hollow cage
• what is the maximum size of a nanoparticle?

  1-100nm