Fractions
Properties of fractions
Each Mixture of hydrocarbons, mainly alkanes, formed over millions of years from the remains of ancient dead marine organisms. In fractional distillation, such as that of crude oil, the different parts of the original mixture are called fractions. The substances in each fraction have similar boiling points to each other. contains a Two or more substances that are not joined together. The substances can be elements, compounds, or both. of A compound that contains hydrogen and carbon only.. The hydrocarbons in a fraction are mostly hydrocarbons called Saturated hydrocarbon. A compound of hydrogen and carbon only, with no C=C bonds.. They have similar (but not identical):
- numbers of hydrogen and carbon atoms in their A collection of two or more atoms held together by chemical bonds.
- The temperature at which a substance rapidly changes from a liquid to a gas.
- ease of Set on fire.
- A measure of how difficult it is for a substance to flow - the higher the viscosity, the 'thicker' it is.
For example, the gases fraction contains hydrocarbons with one to four carbon atoms. These have:
- boiling points below room temperature
- they are very Able to ignite and burn.
- have a low viscosity
The A compound that contains hydrogen and carbon only. in different fractions differ in these properties. For example, the bitumen fraction contains hydrocarbons with more than 35 carbon atoms. These have:
- boiling points well above room temperature
- are very difficult to ignite
- have a high viscosity
Hydrocarbon Material that is used to produce heat, like coal, oil or gas. can undergo Burning in a plentiful supply of oxygen or air. Complete combustion of a hydrocarbon produces water vapour and carbon dioxide. or Burning when there is a limited supply of air or oxygen., depending on the amount of oxygen available.
Complete combustion
Complete combustion of a hydrocarbon fuel happens when there is a good supply of air. Carbon and hydrogen atoms in the fuel react with oxygen in an Reaction in which energy is given out to the surroundings. The surroundings then have more energy than they started with so the temperature increases. reaction:
- A gaseous compound of carbon and oxygen, which is a by-product of respiration, and which is needed by plants for photosynthesis. and water are produced
- the maximum amount of The capacity of a system to do work or the quantity required for mechanical work to take place. Measured in joules (J). For example, a man transfers 100 J of energy when moving a wheelbarrow. is given out
In a Bunsen burner, this occurs when the air hole is fully open.
In general:
hydrocarbon + oxygen → carbon dioxide + water
Here are the equations for the complete combustion of propane, used in bottled gas:
propane + oxygen → carbon dioxide + water
C3H8 + 5O2 → 3CO2 + 4H2O
Question
Write a balanced equation for the complete combustion of methane, CH4, found in natural gas.
CH4 + 2O2 → CO2 + 2H2O
Incomplete combustion
Incomplete combustion happens when the supply of air or oxygen is poor. Water is still produced, but Poisonous gas produced during incomplete combustion. and carbon are produced. Less energy is released than during complete combustion.
In a Bunsen burner, incomplete combustion occurs when the air hole is closed.
You will learn more about incomplete combustion in this study guide on atmospheric pollution.