Properties of small covalent molecules

• Small covalent molecules

  Molecules with a small number of atoms, e.g. methane with 5 atoms
• Small covalent molecules

  • Have low melting and boiling points
  • Are usually gases or liquids at room temperature
• Water is a liquid at room temperature but has a relatively low boiling point of 100°C
• Why small covalent molecules have low melting and boiling points

  1. Atoms in each molecule are held together by strong covalent bonds

  2. There are very weak intermolecular forces between molecules

  3. As temperature increases, vibration of molecules increases

  4. At a certain point, vibration is strong enough to break the weak intermolecular forces, causing the substance to boil
• As the size of the covalent molecule increases

  The intermolecular forces increase, requiring more energy to break and resulting in higher boiling points
• Small covalent molecules do not conduct electricity
• Reason small covalent molecules do not conduct electricity

  They do not have an overall electric charge
• You'll find plenty of questions on this topic in the revision workbook