C9 Flashcards
What are Hydrocarbons?
Fuels are important because they keep you warm and on the move. So when oil prices rise, it affects everyone. Countries that produce crude oil can affect the whole economy by the price they charge for their oil.
What is Crude Oil?
Crude oil is a finite resource found in rocks. It was formed over millions of years from the remains of tiny, ancient sea animals and plants, mainly plankton, that were buried in mud. Over time, layer upon layer of rock was laid down on top, creating the conditions (high pressure and temperature, in the absence of oxygen) to make crude oil. Crude oil is a dark, smelly liquid.
What is Alkanes?
Most of the hydrocarbons in crude oil are ALKANES. You can see some examples of alkane molecules.
The first part of the name of each alkane tells you how many carbon atoms are in its molecules.
What are the properties of hydrocarbons?
There is a great variety of hydrocarbon molecules. Some are quite small, with relatively few carbon atoms in short chains. These short-chain molecules make up the hydrocarbons that tend to be most useful.
What is fractional distillation of crude oil?
Crude oil is separated into hydrocarbons with similar boiling points, called fractions. This process is called FRACTIONAL DISTILLATION.
What is complete combustion in burning hydrocarbon fuels?
The lighter fractions from crude oil are very useful as fuels. When hydrocarbons burn in plenty of air they transfer lots of energy to the surroundings. THE PRODUCTS OF THE COMPLETE COMBUSTION OF A HYDROCARBON ARE CARBON DIOXIDE AND WATER.
What is incomplete combustion?
All fossil fuels- oil, coal, and natural gas- produce carbon dioxide and water when they burn in plenty of air. However, when there is not enough oxygen. For example, inside an engine, there is a incomplete combustion.
Whats happens in complete combustion?
The carbon and hydrogen in the fuel are oxidised completely when they burn like this. Remember that one definition of oxidation means adding oxygen in a chemical reaction.
Why crack hydrocarbons?
Some of the heaviest from the fractional distillation of crude oil are not in high demand. The hydrocarbons in them are made up of large molecules. They are thick liquids or solids with high boiling points. They are difficult to vaporise and do not burn easily - so they are poor fuels, although they do have their uses. Yet the main demand from crude oil is for fuels and starting materials (feedstock) for the chemical industry. Fortunately, the larger, less useful hydrocarbon molecules can be broken down into smaller, more useful ones in a process we call cracking. The hydrocarbons are cracked as THERMAL DECOMPOSITION reactions take place. The large molecules split apart to form smaller, more useful ones.
What is an example of cracking?
The other molecules in this reaction have names that end slightly differently. They end -ene. We call this type of molecule an ALKENE. The different ending tells us that three molecules are unsaturated. Unsaturated compounds contain at least a DOUBLE BOND between the carbon atoms.
What is a positive test for unsaturated hydrocarbon?
It goes from orange bromine, it turns colourless.
What do tests on the gaseous products show about alkenes?
They burn in air (but not as well as equivalent small alkanes which are used as fuels)
React with bromine water, which is orange in colour, decolourising it.
