Properties of small molecules



Worksheet ANS

Resource Videos


Water tension

intro into intermolecular forces


Water tension

intro into intermolecular forces

Practical Properties of small molecules

Demonstration - water tension

  • Bowl for water - and then milk
  • Milk
  • Food colouring
  • Pepper (from grinder or shaker)
  • Cuetip - and soap

1)Demo video for food colouring - same idea with water and pepper

Risk :


BreakingWaterBonds.mp4 Properties of small molecules


  • Substances that consist of small molecules are usually gases or liquids that have relatively low melting points and boiling points.

These substances have only weak forces between the molecules (intermolecular forces). It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils.

The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.

These substances do not conduct electricity because the molecules do not have an overall electric charge.

Students should be able to use the idea that intermolecular forces are weak compared with covalent bonds to explain the bulk properties of molecular substances.

WS 1.2 Use a variety of models such as representational, spatial, descriptive, computational and mathematical to solve problems, make predictions and to develop scientific explanations and understanding of familiar and unfamiliar facts.