Friday pHunday
ALKANES AND ALKENES
(HSC 2002 Q17, 3 marks)
Explain why alkanes and their corresponding alkenes have similar physical properties,
but very different chemical properties (3 marks)
Explain
relate cause and effect; make the relationships between
things evident; provide why and / or how.
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HSC 2002 - Q17
Physical Properties: Cause: Both alkanes and alkenes are non polar hydrocarbon
molecules. Effect: Their dipoles are arranged symmetrically so they cancel each other
out (the dipoles do not reinforce each other). As a result, their strongest intermolecular
forces are dispersion forces. Physical properties including melting and boiling point and
solubility are dictated by these forces. So physical properties in alkanes and alkenes
are similar.
Chemical Properties. Cause: Alkanes have single carbon-carbon covalent bonds and
are therefore saturated. Alkenes have at lease one carbon-carbon double bond and are
unsaturated. Effect: Alkanes are therefore less reactive chemically than alkenes.