PREDICTED P1

• Explain why the mass of an atom does not change when it gains or loses electrons. (2marks)

  • Electrons have no mass.
  • Mass is determined by protons/neutrons.
• Explain how isotopes differ from one another (2 marks)

  • Isotopes have the same number of protons/electrons
  • But different neutrons
• Describe the differences between a chlorine atom and a chloride ion. (2 marks)

  • Chloride ion has a negative charge.
  • Chlorine has no charge.
• Explain why sodium and chlorine are able to form ionic compounds whilst sodium and helium cannot (2 marks)

  • Helium is inert as it has a full outer shell.
  • Chlorine is highly reactive with sodium
• Describe and explain the trend in reactivity as you move down the halogens in the periodic table (3 marks)

  • Reactivity decreases going down the group
  • Because the distance between the outer electron and the nucleus increase
  • So it is harder to gain another electron.
• Explain why Mendeleev left gaps in his periodic table (2 marks)

  • Left gaps for undiscovered elements
  • As he organised elements by trends/properties.
• Describe two features of the nuclear model of the atom (2 marks)

  • fixed energy shells
  • negative electrons.
• Explain the melting point of diamond. (2 marks)

  • Giant covalent bonds- strong.
  • Takes lots of energy to overcome these strong bonds.
• Compare the bonding of carbon in graphite and diamond (4 marks)

  • Graphite: 3 carbon bonds
  • Graphite: Layered structure
  • Diamond: 4 carbon bonds
  • Diamond: repeating structure
• Give a range of sizes between which particles may be considered nanoparticles.

  1-100 nm
• What happens during a neutralisation reaction? (2 marks)

  • An acid and a base react
  • To form a neutral solution.
• Describe the properties of a strong acid (2 marks)

  • fully dissociates
  • pH below 3
• Describe an experiment that identifies the unknown ion (either copper or magnesium) in the electrolyte. (6 marks)

  • Use inert electrodes in electrolyte.
  • Voltage applied.
  • PANIC
  • Gas produced at cathode suggests magnesium as it is more reactive than hydrogen.
  • No gas produced at cathode indicates copper as its less reactive than hydrogen.
  • Hydrogen gas identified by squeaky pop.
  • Oxygen identified by glowing splint.
  • Halogen identified by litmus test.
• Suggest one safety precaution for electrolysis

  • Goggles
• Suggest one control variable for electrolysis

  • voltage
  • temp
  • concentration of electrolyte
• State and explain what state the electrolyte for an electrolysis experiment should be (2 marks)

  • Liquid
  • As the ions should be free to move around and carry a charge.
• Suggest two factors that will affect the voltage of an electrochemical cell.

  • Material used for electrodes
  • Concentration of electrolyte.
• Explain the chemistry that enables some batteries to be rechargeable (3 marks)

  • Electrode reactions are reversible
  • Starting materials are regenerated during charge
  • So the forward reactions can happen again.
• Give one advantage and disadvantage of using a hydrogen oxygen fuel cell

  • DISADVANTAGE: Hydrogen is highly flammable/explosive
  • ADVANTAGE: Does not produce greenhouse pollutants.
• Explain how energy is stored in a chemical compound (1 mark)

  • In chemical bonds