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
• Small covalent molecules

  • Methane
  • Other molecules shown in the video
• Water is an exception, being a liquid at room temperature despite having 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 covalent molecules increases

  The intermolecular forces increase, requiring more energy to break and resulting in higher boiling points
• Small covalent molecules do not conduct electricity
• More questions on these topics can be found in the revision workbook