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CHEMISTRY, M1 EQ-Bank 37

  1. Draw Lewis dot diagrams for both water AND methane.   (2 marks)
  1. Methane has a boiling point of -161.5°C, while water has a melting point of 0°C and a boiling point of 100°C.
  2. Account for the differences in these physical properties for these TWO common substances in our atmosphere.   (2 marks)

Show Answers Only

a.    (insert image here)

 

 b.    The differences in the physical properties of methane and water can be explained by the differences in their molecular structures and intermolecular forces.

→ Methane (\(\ce{CH4}\)) is a nonpolar molecule with weak dispersion forces between its molecules. These weak forces result in a very low boiling point of -161.5°C.

→ Water (\(\ce{H2O}\)), on the other hand, is a polar molecule that forms strong hydrogen bonds between its molecules. These strong intermolecular forces which require more energy to be broken resulting in much higher melting and boiling points (0°C and 100°C, respectively).

Show Worked Solution

a.    (insert image here)

→ All electrons must be shown as dots, not crosses, circles, etc.

→ No lines should be present to represent covalent bonds.

 

b.    The differences in the physical properties of methane and water can be explained by the differences in their molecular structures and intermolecular forces.

→ Methane (\(\ce{CH4}\)) is a nonpolar molecule with weak dispersion forces between its molecules. These weak forces result in a very low boiling point of -161.5°C.

→ Water (\(\ce{H2O}\)), on the other hand, is a polar molecule that forms strong hydrogen bonds between its molecules. These strong intermolecular forces which require more energy to be broken resulting in much higher melting and boiling points (0°C and 100°C, respectively).