Molecular Substances

• Molecule


  Two or more atoms held together by covalent bonds
• State of molecular substances at room temperature

  Liquids or gases
• Van der Waals forces

  Weak forces of attraction between molecules

  
• Melting and boiling points of molecular substances

  Low
• Reason for melting and boiling points of molecular substances

  Van der waals forces are weak.
• Trends in Van der Waals

  The larger the molecule the stronger the Van der Waals
• Electrical conductivity of molecular substances

  Low conductivity
• Reason for electrical conductivity of molecular substances

  Molecules are neutral
• Covalent bonds


  A shared pair of electrons

  
• Solubility of small molecules

  Insoluble in water
• Soluble molecules


  Hydrochloric acid, ammonia
• Reason some molecules are soluble

  They react with water