Atmosphere BY JACK HARFIELD

The gases in the atmosphere The common name air is given to the atmospheric gases used in breathing and photosynthesis. By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases.

This is the carbon cycle as this how we get oxygen and carbon dioxide in to are atmosphere.

Cracking BY JACK HARFIELD

Where does cracking take place  In order for it to be useful to us, crude oil is broken down in oil refineries into its component parts, known as fractions, and these can then be used for many different purposes.  Fractions that are produced by the distillation of crude oil can go through a process called cracking. This chemical reaction produces smaller hydrocarbons, including alkanes and alkenes. Ethene and other alkenes are unsaturated hydrocarbons and can be used to make polymers. Ethene can be used to make ethanol.  Cracking  Fuels made from oil mixtures containing large hydrocarbon molecules are not efficient. They do not flow easily and are difficult to ignite. Crude oil often contains too many large hydrocarbon molecules and not enough small hydrocarbon molecules to meet demand - this is where cracking comes in.  Cracking allows large hydrocarbon molecules to be broken down into smaller, more useful hydrocarbon molecules. Fractions containing large hydrocarbon molecules are vaporised and passed over a hot catalyst. This breaks chemical bonds in the molecules, and forms smaller hydrocarbon molecules.  Cracking is an example of a thermal decomposition reaction.

What conditions are required for cracking  fuels made from oil mixtures containing large hydrocarbon molecules are not efficient: they do not flow easily and are difficult to ignite. Crude oil often contains too many large hydrocarbon molecules and not enough small hydrocarbon molecules to meet demand. This is where cracking comes in.  Cracking allows large hydrocarbon molecules to be broken down into smaller, more useful hydrocarbon molecules. Fractions containing large hydrocarbon molecules are heated to vaporise them. They are then either:  passed over a hot catalyst, or  mixed with steam and heated to a very high temperature.  These processes break chemical bonds in the molecules, causing thermal decomposition reactions. Cracking produces smaller alkanes and alkenes (another type of hydrocarbon).

What is produced during cracking  Longer chain molecules are broken down and produced smaller chain molecules. The shorter chain molecules are used for different things and the smaller chain molecules have a smaller chain molecule have a low boiling point.