Water

Introduction

This topic explores the key concepts of water as they relate to:

  • functional uses of water
  • properties of water
  • solutes, solvents and solutions
  • solubility and concentration
  • reactions in solution.

Key concepts of water:

The activities in this topic are designed to explore the following key concepts:

  • Water is an essential component of all living things.
  • Water is a good solvent.
  • Water exists as molecules of H2O.
  • The water molecule is polar in structure; this concept explains many of water's properties.
  • Water has relatively high melting and boiling points.
  • Water expands on freezing. Ice is less dense than liquid water.
  • Large amounts of energy (latent heat) are required for a change of state of water.

Students' alternative conceptions of water

Research into students' ideas about this topic has identified the following non-scientific conceptions:

  • Water is something different from H2O molecules.
  • Water molecules have different sizes and shapes.
  • There is no space between water molecules in ice.
  • Water vapour molecules weigh less than ice molecules.
  • The 'skin' of a water drop or water surface is a different kind of water.
  • Oil doesn't mix with water because oil and water molecules repel each other.
  • Water molecules are largest and heaviest when in the solid phase.
  • Water molecules can be seen with an optical microscope.

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