Write a balanced symbol equation to show methane burning in oxygen CH4+ 2 O2  CO2 + 2 H2O methane + oxygen  carbon dioxide + water

Chemistry for a sustainable world – C7 The alkanes Learning Objectives: To be able to write a balanced equation for the combustion of a hydrocarbon. To know what alkanes and alcohols are. Key words: hydrocarbon, combustion, alkane, alcohol

What are all these? Paraffin wax Butane gas Candle wax

Activity – More about alkanes Complete activity 1+2 on Ac7.1. For each model write down the molecular formula. What is the relationship between number of carbon atoms and number of hydrogen atoms in each alkane? Try to write down a general formula to show the number of carbon and hydrogen atoms in an alkane. Use the table in activity 3 on Ac7.1 to describe in words how the boiling point of an alkane varies with chain length. Watch the demonstrations and make observations as shown in activity 4 on Ac7.1. Now explain why alkanes are so unreactive.

Alkanes – Summary Alkanes CnH2n+2 (n = 1, 2, 3 etc) Alkanes are SATURATED molecules because they contain ONLY single bonds (every carbon is attached to 4 different atoms). Alkanes are generally very unreactive. Alkanes do not mix with water. Alkanes burn with a smokey flame. Alkanes are used as fuels and can be solid (candle wax), liquid (hexane) or gas (propane gas, butane gas)

Changing the reactivity by changing the atoms…. R is an alkane chain Look at the models of methanol and ethanol to see how they are different NOT industrial alcohol as used in the lab!!

Alcohol family summary OH is a functional group. Functional groups give compounds their different chemical and physical properties. In this case, the OH group makes alcohols more reactive than alkanes. E.g. They burn with a blue flame. OH here is not OH- ion because it is COVALENTLY bonded not IONIC here!!