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Explain why alkanes and their corresponding alkenes have similar physical properties, but very different chemical properties. - HSC - SSCE Chemistry - Question 17 - 2002 - Paper 1
Question 17
Explain why alkanes and their corresponding alkenes have similar physical properties, but very different chemical properties.
Worked Solution & Example Answer:Explain why alkanes and their corresponding alkenes have similar physical properties, but very different chemical properties. - HSC - SSCE Chemistry - Question 17 - 2002 - Paper 1
Step 1
Similar physical properties
Answer
Alkanes and alkenes both contain carbon and hydrogen atoms, which allows them to exhibit similar physical properties, such as boiling points and solubility. These similarities arise because both classes of compounds are non-polar and have similar molecular sizes. The presence of London dispersion forces also contributes to their comparable boiling points. Consequently, as the number of carbon atoms increases in both alkanes and alkenes, their physical properties, such as density and boiling point, tend to become more similar.
Step 2
Different chemical properties
Answer
The chemical properties of alkanes and alkenes differ significantly due to the presence of double bonds in alkenes. Alkanes are saturated hydrocarbons, meaning they contain only single bonds between carbon atoms, which makes them relatively unreactive. In contrast, alkenes are unsaturated due to their carbon-carbon double bond, which makes them more reactive. This double bond allows alkenes to undergo addition reactions, such as hydrogenation and halogenation, which do not occur in alkanes. Consequently, the fundamental structural differences lead to distinct chemical behaviors between the two families of compounds.