Properties of Water
Learning Objectives
Trends in the melting and boiling points of Group 16 hydrides, with reference to the nature and relative strengths of their intermolecular forces and to account for the exceptional values for water
Summary Notes
Water is a polar molecule.
The oxygen end is slightly negative compared to hydrogen because of it's greater affinity for electrons.
The main intermolecular force present between water molecules is hydrogen bonding.
Water is a liquid at room temperature because the hydrogen bonds between the water molecule attract enough so that they behave as a liquid.
Water expands as it freezes because the molecules need arrange in a way where each water molecule forms four hydrogen bonds to four neighbouring water molecules.
This causes water to be denser in liquid than solid state.
Water in solid (A), liquid (B) and gas (C) form
Boiling and melting points of Group 16 hydrides (researchgate.net)
Boiling temperature increases going down group 16 from H₂S to H₂Te because the dispersion force is getting stronger with increasing molecular mass.
Water has a high melting and boiling point.
More heat (energy) is required to break hydrogen bonds between water molecules.
The breaking of hydrogen bonds allow for the formation of water in its various states.
Videos to help build your understanding
How polarity makes water behave strangely
Practice Material
Teacher's Tip:
A lot of the properties of water can be explained by it's strong hydrogen bonding. If you ever have a mental block during a quiz/test, use this knowledge to solve that question.