C7 chemistry revision

C7 Chemistry for a sustainable world

1a The Alkanes

Alkanes are made up of Hydrocarbons (molecules of hydrogen and carbon) Examples of Alkanes are Candle wax. Notice how they do not mix with water.

These are some of the Alkanes;

Methane CH4

Ethane C2H6

These are some of them however there are more you should know about.

The physical properties of Alkanes are that they are oily, and since they are oily they dont dissolve or mix with water.

To find out what state the alkane is at room temperature this is how you know;

Alkanes with up to 4 carbons are gases

Alkanes with 4-17 carbons are liquid

and Alkanes with more than 17 Carbons are solids

All Alkanes burn, this is why fuells consist mainl of Alkanes, they also burn in Air (oxygen) forming Carbon Dioxide and water.

However Alkanes do not react with Acids or Alkali or any other common aqueous reagents because the bonds C-C and C-H are unreactive

1B The Alcohols

Ethanol is the best-known member of the series of Alcohol, it is mainly found in Beers, wine and Spirit. It is also used in perfumes because the liquid evaporates quickly, however ethanol catches fire easily (flammable)

Methanol another alcahol can be made in two steps from methane and steam. it is used as adhensive, foams and windscreen washer fluids.

The alcohol can be seen as a Alkane however the Hydrogen is replaced by an OH, this is the functional groups for Alcohol.

Alcahols are liquid at room temerature, whereas the alkanes was gases at room temperature, (look at methane and methanol) the presence of the OH gives the molecules the greater tendency to cling together like water.

However the attractions between hydrocarbon part are very weak as in alkanes. likewise in Alkanes the hydrogen part of the molecules dominates that is why they do not mix with water (oily)

All alcohol burn because of the hydrogen

The OH bond is the reactive part of the molecule.