9.8 – NOTES Alkane Boiling Points

A.10 Boiling Points of Alkane Isomers The more branches, the lower the boiling point Why are boiling points lower for branched chain? More branches result in a more compact shape; this makes fewer intermolecular contacts (shorter chains) and makes the molecules more easily separated from each other

Viscosity Resistance to flow The more viscous something is, the less easily it flows Viscosity and Temperature Temperature can affect viscosity of a substance When you increase the temperature of the fluid, the viscosity decreases, or flows more easily. Heat goes up, viscosity goes down  

A.11 Fuels and Climate Different parts of the country have different climates, resulting in different fuel additives added Automobile fuel used in Maine during the cold winter months differs from the fuel used in Arizona during hot summer  

Why do different areas need different types of fuel? Volatility affects performance Warmer climates need fuels that don’t easily vaporize (vapor lock) Colder climates need fuels that don’t solidify or become viscous

What physical property should be engineered to make the fuel appropriate for each climate? Volatility Viscosity   Molecular structure is used to vary properties to make the different chemical substances for the various materials made from petroleum