Course 8.3Lesson 1 of 3
Carbon compounds burn to give carbon dioxide, water, heat and light. Saturated hydrocarbons burn with a clean blue flame in plenty of air, and unsaturated ones burn with a yellow sooty flame. Alcohols are oxidised to acids. Unsaturated compounds undergo addition, and saturated ones undergo substitution.
Try the code and the simulations beside the lesson.
Carbon compounds burn in oxygen and give carbon dioxide, water, heat and light. This is combustion.
Why? An unsaturated compound has a bigger share of carbon. In ethane the share of carbon is by mass. In ethene it is and in ethyne it is . At the usual air supply there is not enough oxygen for all the carbon. Some is left as soot, and the glowing carbon particles make the flame yellow.
If a gas stove or a lamp burns with a yellow flame and black soot on the pan, the air holes are blocked. There is incomplete combustion, and it can make the poisonous gas carbon monoxide.
Coal and petroleum have some sulphur and nitrogen, and they burn to make oxides of these, which cause acid rain.
You should find that, for the same carbon atoms, fewer hydrogens mean a bigger share of carbon. Every alkene has the same share, .
Some substances can add oxygen to carbon compounds. These are oxidising agents, such as alkaline potassium permanganate and acidified potassium dichromate. They change an alcohol to a carboxylic acid.
An unsaturated hydrocarbon adds hydrogen at the double or triple bond, with a nickel or palladium catalyst. The double bond becomes a single bond.
This is used to change vegetable oils, which are unsaturated, into saturated fats, such as the vanaspati ghee. It is hydrogenation.
A saturated hydrocarbon is quite unreactive. In sunlight, it reacts with chlorine, and a chlorine atom takes the place of a hydrogen atom.
This program finds the share of carbon in some hydrocarbons.
Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.
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