Alcohols and Acids

Two families to know

This module covers two families of carbon compounds. Alcohols all contain the -OH group and their names end in -ol, such as methanol and ethanol. They are used as fuels, solvents and in drinks. Carboxylic acids all contain the -COOH group and their names end in -oic acid, such as methanoic acid and ethanoic acid. You will learn how alcohols are made and how they burn, and how carboxylic acids behave as weak acids. The alkenes are covered in a separate module, so they are not the focus here.

Words for the two families

Learn these before you sort any compound or reaction.

Two ways to make ethanol

Ethanol can be made in two very different ways. Telling them apart is a common exam question, so learn the conditions for each.

How to name and sort

Use two clues together to place any compound: the functional group it carries and the ending of its name. One family shares one group and one name ending; the other family shares a different group and a different ending, which you met in the words step. Work from those two clues rather than guessing. For a reaction, ask what new substances form and whether a gas bubbles off, and let the products point you to what the reaction was.

Match the alcohol to its formula

What makes an acid weak?

Ethanoic acid is described as a weak acid. What does weak mean here?

• It only partly ionises in water, releasing few hydrogen ions.
• It is always very dilute in water.
• It can never harm or corrode anything.
• It has no functional group at all.

True of alcohols?

Select the TWO statements that are true of alcohols.

• They contain the -OH functional group
• They burn in air, releasing energy
• They contain the -COOH group
• They are metals

Count the hydrogen atoms

Ethanol has the formula C2H5OH. The C2H5 part has 5 hydrogen atoms and the OH part has 1 more. Add them to find the total number of hydrogen atoms in one molecule of ethanol. What is the answer?

Order the fermentation steps

Put the steps of making ethanol by fermentation in order, earliest first.

• Mix sugar with yeast in water
• Keep it warm and seal it away from air
• The yeast turns the sugar into ethanol and carbon dioxide
• Distil the mixture to concentrate the ethanol

Complete the facts

Alcohols all contain the _____ functional group and their names end in -ol. Ethanol can be made by fermentation of sugar using _____. Carboxylic acids all contain the _____ functional group. In water they are _____ acids because they only partly ionise.

Match the reaction to its product

Spot the true alcohol facts

Tap the TWO statements that are true about alcohols and carboxylic acids.

• Alcohols contain the -OH group and end in -ol
• Carboxylic acids are weak and only partly ionise
• Carboxylic acids are strong and fully ionise
• Alcohols cannot be used as fuels

Identify the compound

Read each clue and choose the compound it describes.

• A compound has the -OH group, ends its name in -ol, and burns well as a fuel. Which family is it?
• A compound has the -COOH group, only partly ionises in water, and fizzes when added to a carbonate. Which family is it?
• A factory makes ethanol in a continuous process by reacting ethene with steam over a catalyst at high pressure. Which method is this?

Explain alcohols and acids

Explain the alcohols and the carboxylic acids, including how each family is recognised and how ethanol can be made.

• Name the functional group and name ending of an alcohol
• Explain the two ways ethanol can be made and how they differ
• Name the functional group of a carboxylic acid and explain why it is a weak acid
• Give one reaction of a carboxylic acid and its product