GCSE Chemistry
Organic Chemistry 1
Ethanol is a type of alcohol that we drink.
This is the first of our GCSE Chemistry quizzes on organic chemistry. Over ninety percent of all chemical compounds are classified as organic compounds. They were given this name because scientists once thought that they could only be made naturally - not unnaturally by scientists in a laboratory. However, in 1828, Friedrich Wohler made the naturally occurring organic compound urea in his laboratory which opened the door to making others from simpler materials.
But what exactly is organic chemistry? Essentially, it is the chemistry of carbon compounds but keep in mind that not all carbon compounds are organic chemicals, for example, carbon dioxide. Essentially, an organic compound contains at least one carbon atom in the compound that is joined to at least one hydrogen atom. If a molecule contains chains of two or more carbon atoms, bonded to each other and to other elements, that is also recognised as being an organic chemical. Organic compounds are always covalent, but some can show some slight charateristics of ionic compounds e.g. soluble in water.
Organic chemicals can be grouped into families which contain compounds with similar properties. This happens because they are based on chains of carbon atoms. Take for example the alkane family. Methane is the simplest alkane and has one carbon atom. Ethene has two carbon atoms and its properties are very similar to methane. Octane has eight carbon atoms and although it is a liquid and not a gas like methane and ethane, it still has similar chemical properties to those two substances. There is a general formula that can be used to predict the exact formula of any member of a family of organic chemicals.
For your GCSE exam, you will learn about the alkane and alkene family as you study crude oil. You will also learn about polymers that are made from organic chemicals. In addition to these, you are expected to know about three other organic chemical families - the alcohols, carboxylic acids and esters. You will need to be able to recognise and represent the structures of alcohols and carboxylic acids in the form of structural formulae and also as the more familiar chemical formulae. You may be given data and other information in your exam and asked to evaluate and compare the social and economic advantages and disadvantages of these chemicals. You won't be asked to remember the names of more than a few of these chemicals, different exam boards have slightly different requirements but your teacher will make it clear which you need to know.
What type of bonds are formed between carbon and hydrogen atoms in organic molecules?
Carbon and hydrogen are both non-metals, so form covalent bonds
What is the general formula for alcohols?
CnH2nOH
CnHn+1OH
CnH2n+1OH
CnH2n+1O
With this general formula, you can work out the formula of other alcohols
If an alkane contains 24 hydrogen atoms, how many carbon atoms does it have?
24 - 2 = 22 / 2 = 11
Which of the alcohols below has the molecular formula C4H9OH?
Propanol
Butane has 4 carbons, so does butanol
If there are 8 carbon atoms in an alcohol molecule, how many hydrogen atoms are there?
2 x 8 + 1 + 1 (from OH) = 18
The alcohols are a family of organic compound that has a wide range of uses, including drinking. Which of the following alcohols is the only one that we drink?
Ethanol also has other uses such as in biofuels
The general formula for alkanes is CnH2n+2. If an alkane contains 6 carbon atoms, how many hydrogen atoms are present?
6 x 2 + 2 = 14
If an alkene has 24 hydrogen atoms, how many carbon atoms does it contain?
24 / 2 = 12
All organic compounds contain which element?
Organic chemistry is all about compounds of carbon
The general formula for alkenes is CnH2n. If an alkene contains 7 carbon atoms, there are how many hydrogen atoms in the compound?
Author: Kate Gardiner
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