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What is ethanol, how is it made, and why is it such a widely used substance?

Describe ethanol as a member of the alcohols, state how it is made by fermentation, and describe its main uses including as a fuel and solvent

A focused answer to the N(A) Chemistry outcome on alcohols. Ethanol as a member of the alcohol family, how fermentation makes it, that it burns exothermically, and its uses as a fuel, drink and solvent.

Generated by Claude Opus 4.88 min answerUpdated 2026-06-06

Reviewed by: AI editorial process; not yet individually human-reviewed

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What this dot point is asking

The syllabus wants you to describe ethanol as a member of the alcohols, to state how it is made by fermentation, and to describe its main uses, including as a fuel and a solvent. The key facts are that all alcohols share a common feature (the $\text{-OH}$ group), that fermentation uses yeast to turn sugar into ethanol, and that ethanol burns exothermically, which makes it useful as a fuel.

The answer

Ethanol and the alcohols

The alcohols are a family of compounds that all contain an $\text{-OH}$ group (an oxygen joined to a hydrogen). The most common is ethanol, with the formula $\text{C}_2\text{H}_5\text{OH}$ . Ethanol is the alcohol found in alcoholic drinks, but it has many other uses too.

Making ethanol by fermentation

Fermentation makes ethanol from sugar using yeast. Yeast is a living micro-organism that contains enzymes which break down the sugar:

\text{glucose} \rightarrow \text{ethanol} + \text{carbon dioxide}

For fermentation to work well it needs:

yeast (which provides the enzymes),
a warm temperature (around body temperature; too hot kills the yeast, too cold and it is slow),
no air (anaerobic conditions).

The carbon dioxide given off makes the mixture bubble.

Ethanol as a fuel

Ethanol burns easily in air, and burning it is exothermic (gives out a lot of heat). Complete combustion gives carbon dioxide and water:

\text{ethanol} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water}

Because it burns cleanly and can be made from crops, ethanol is used as a fuel, sometimes mixed with petrol for cars.

Ethanol as a solvent and in drinks

Ethanol is a good solvent, meaning it dissolves many substances that water cannot. This is why it is used in perfumes, deodorants, hand sanitiser and many cleaning products. It is also the alcohol in alcoholic drinks, though drinking too much is harmful.

Following the fermentation of sugar

A student mixes glucose solution with yeast, keeps it warm, and seals it from the air. Describe what happens and how they would know it is working.

Step 1: Identify the ingredients and conditions

The mixture has sugar (glucose) and yeast, is kept warm, and is sealed to keep air out, which are the conditions fermentation needs.

Step 2: State the reaction taking place

The yeast's enzymes break down the glucose into ethanol and carbon dioxide.

Step 3: Describe the visible sign

Bubbles of carbon dioxide are given off, so the mixture fizzes. Bubbling the gas through limewater would turn it milky, confirming carbon dioxide.

Step 4: State the product and how to obtain it

Ethanol builds up in the mixture. Because ethanol boils at a lower temperature than water, it can be separated afterwards by distillation to get a more concentrated ethanol.

Examples in context

Example 1. Bioethanol in petrol. Many countries blend ethanol made by fermenting crops into petrol to make a partly renewable fuel. Because ethanol burns to give out heat, it can help power cars while reducing the amount of fossil fuel used.

Example 2. Hand sanitiser. Alcohol-based hand sanitisers rely on ethanol as a solvent and disinfectant that evaporates quickly and kills germs. This everyday product, used widely during illness outbreaks, is a direct application of ethanol's properties.

Try this

Q1. Name the two substances needed to make ethanol by fermentation. [2 marks]

Cue. Sugar (glucose) and yeast.

Q2. State the two products formed when sugar is fermented. [2 marks]

Cue. Ethanol and carbon dioxide.

Q3. State one use of ethanol as a fuel and one use as a solvent. [2 marks]

Cue. As a fuel, it can be burned (for example mixed with petrol) to give out heat; as a solvent, it is used in products such as perfume or hand sanitiser.

Exam-style practice questions

Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

Original5 marksEthanol can be made by fermentation. (a) Name the substance (sugar) and the living thing needed for fermentation. (b) State the two products of fermentation. (c) State one condition needed for fermentation to work well.

Show worked answer →

(a) Fermentation needs sugar (glucose) and yeast.

(b) The products are ethanol and carbon dioxide.

(c) A warm temperature is needed (around body temperature); the absence of air (anaerobic conditions) is also acceptable.

What markers reward: sugar/glucose and yeast, ethanol and carbon dioxide as products, and a warm temperature (or no air) as a condition.

Original4 marksEthanol is used as a fuel and as a solvent. (a) State what is produced when ethanol burns completely in plenty of air. (b) State why ethanol is described as a good fuel. (c) State one everyday use of ethanol as a solvent.