Physical Properties

  • Small molecules are compounds made up of molecules that contain just a few atoms covalently bonded together.
  • They have low melting and boiling points as there are only weak intermolecular forces acting between the molecules.
  • These forces are very weak when compared to the covalent bonds and so most small molecules are either gases or liquids at room temperature, often the liquids are volatile.
  • Most covalent compounds are insoluble in water as they tend to be non-polar but can dissolve in organic solvents.
  • Some do dissolve in water by forming intermolecular attractions between the water molecules. Examples include sucrose (common sugar C12H22O11) and CO2.
  • As molecules increase in size the intermolecular forces also increase as there are more electrons.
  • This causes the melting and boiling points to increase.
  • They are poor conductors of electricity as there are no free ions or electrons to move and carry charge.
  • Most covalent compounds do not conduct at all in the solid state and are thus insulators.
  • Common insulators include the plastic coating around household electrical wiring, rubber and wood.

Electrical wire insulator, IGCSE & GCSE Chemistry revision notes

Diagram showing plastic coating surrounding metal wires in an electrical cable

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Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.