Polymers & Small Molecules

Topic 2 - Bonding Structure & Properties of Matter
Written By Atheridge Tuition

Figure 1 shows the structures of a methane molecule and an octane molecule.

Methane is a gas at room temperature. Octane is a liquid at room temperature. Explain this difference.

[4 marks]

  • Polymers form small molecules.

    Carbon and hydrogen atoms in methane are bonded with:

    • Strong covalent bonds

    Different methane molecules are held together with:

    • Weak intermolecular forces

Covalent bonds in methane between carbon and hydrogen. There methane molecules with green curly lines to show weak intermolecular forces.

  • We do NOT need to break the covalent bonds!

    To melt/ boil methane we only break the weak intermolecular forces.

Three methane molecules with covalent bonds shown but intermolecular forces are broken with red lines and text reads 'intermolecular forces broken to melt or boil'

  • Much larger molecules. (1 mark)

    So stronger intermolecular forces. (1 mark)

GCSE Chemistry diagram comparing methane and octane, showing that octane has a larger molecular structure and stronger intermolecular forces.

  • More energy is needed to break them. (1 mark)

    So it has a higher boiling point. (1 mark)

Diagram showing that octane molecules have strong intermolecular forces, requiring more energy to separate them, resulting in a higher boiling point and liquid state at room temperature.
Atheridge Tuition
Previous

Negative Ion Tests
Next

Corrosion