States, Structure and Bonding

• What types of bonding affect the melting and boiling points of a substance?

  The types of bonding in a substance affect its melting point and boiling point.
• How does the strength of bonds relate to the amount of heat required to change a substance's state?

  The stronger the bonds, the more heat is required to overcome them and separate the particles.
• What is the difference in bonding between simple covalent substances and metallic substances?

  Simple covalent substances have strong bonds within molecules but weak intermolecular forces, while metallic substances have strong attractions between metal ions and delocalised electrons.
• Why do simple covalent substances melt and boil at low temperatures?

  Because it doesn't take much energy to overcome the weak intermolecular forces between the molecules.
• What causes most metals to have high melting and boiling points?

  The strong attraction between metal ions and the delocalised electron 'sea'.
• What is the reason ionic substances have high melting and boiling points?

  Because the positive and negative ions are strongly attracted to each other, creating strong electrostatic attractions.
• Why do giant covalent substances have very high melting and boiling points?

  Because they are held together by strong covalent bonds that require a lot of energy to break.
• What happens to some giant covalent substances instead of melting?

  Some giant covalent substances sublime, going straight from a solid to a gas.
• How can you predict the structure of a substance based on its melting and boiling points?

  • High melting and boiling points suggest it is not a simple molecular substance.
  • If it does not conduct electricity, it is unlikely to be a metal.
  • If it has high melting and boiling points and does not conduct electricity, it may be a giant covalent structure.
• What can you conclude about substance C if it has a high melting and boiling point and does not conduct electricity?

  Substance C is likely to have a giant covalent structure.
• What is the state of substance D at 1000 °C if its melting point is 801 °C and its boiling point is 1413 °C?

  Substance D will be a liquid at 1000 °C.
• How do you determine the state of a substance based on its melting and boiling points?

  You compare the temperature to the melting and boiling points to see if it is solid, liquid, or gas.
• What are the properties of the four different substances based on their melting and boiling points?

  • Substance A: Melting point -218.4 °C, Boiling point -183.0 °C, Not a good conductor.
  • Substance B: Melting point 1535 °C, Boiling point 2750 °C, Good conductor.
  • Substance C: Melting point 1410 °C, Boiling point 2355 °C, Not a good conductor.
  • Substance D: Melting point 801 °C, Boiling point 1413 °C, Conducts electricity when molten.