Read the following passage. Which answer gives the missing words in the correct order?There are two good reasons for cracking oil __________. Firstly, there just aren't enough fuels like gasoline or _________ in the original crude oil to meet demand. Secondly, _______ that are needed to manufacture other chemicals are not found in oil but can be made from it. Cracking means the vast majority of crude oil can be turned into useful products and not just burnt as ______.

When crude oil is separated into its fractions many of the hydrocarbons can be used as fuels. These range from gasses, like propane and butane, to the heavy fuel oil that is used to power ships. The greater the number of carbon atoms in the hydrocarbon, the more energy it releases when it is burnt. But, despite being a valuable source of energy, there is a downside to using hydrocarbons as fuel. Burning them releases carbon dioxide and other pollutants into the air, causing global warming and other types of environmental damage. When crude oil became widely available in the middle of the... Show more

When crude oil is separated into its fractions many of the hydrocarbons can be used as fuels. These range from gasses, like propane and butane, to the heavy fuel oil that is used to power ships. The greater the number of carbon atoms in the hydrocarbon, the more energy it releases when it is burnt. But, despite being a valuable source of energy, there is a downside to using hydrocarbons as fuel. Burning them releases carbon dioxide and other pollutants into the air, causing global warming and other types of environmental damage.

When crude oil became widely available in the middle of the nineteenth century, it wasn't long before the process of cracking was developed. This is used to break down the longer molecules into smaller and more reactive ones. There are many different ways of cracking crude oil chemicals but the one thing they all have in common is they require high temperatures. In schools, the only method of cracking you are likely to have seen (or done for yourself) is catalytic cracking. In this, a catalyst of broken pot is heated up to a high temperature and when a long molecule (for example those in liquid paraffin) passes over it is broken down to ethene and a smaller alkane. Other methods of cracking use high temperatures, high pressures and steam.

Cracking makes crude oil the source of other things besides fuel. Once cracking had been perfected, scientists found uses for the alkenes that were produced. They could be used to manufacture many new materials. You will probably be most familair with crude oil as a raw material for plastics but it is also used in a wide range of other products like antiseptics, drugs, inks, lubricating oils, fertilizers and many more. The uses of crude oil are expanded greatly by cracking, making it a source of many different products. Cracking is an important process as it enables us to use virtually everything in crude oil.

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