Year 9 Science · Unit 2 · Lesson 05
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Learning Goals
Match each group to a compound that contains it
Write the letter of the matching compound in the middle column.
| Functional group | Letter | Compound |
|---|---|---|
| Hydroxyl group, –OH | A. Propanone, used in nail polish remover. | |
| Carboxyl group, –COOH | B. Ethanol, used in hand sanitiser. | |
| Carbonyl group, C=O, in the middle of a chain | C. Octane, C₈H₁₈, found in petrol. | |
| No functional group: only C and H | D. Acetic acid, which makes vinegar sour. |
1. What is a hydrocarbon? Give one example with its formula.
2. A student is given an unknown compound with the formula C₈H₁₈. Show, step by step, how to decide whether it is organic or inorganic, and state the final classification.
3. Carbonic acid, H₂CO₃, forms when carbon dioxide dissolves in the water of a fizzy drink. Its formula contains carbon and hydrogen, but both hydrogen atoms are bonded to oxygen atoms, not to the carbon atom. A student says carbonic acid must be organic because its formula has both C and H. Is the student right? Explain.
Data: E10 petrol
Australian E10 petrol is 90% petrol (mostly hydrocarbons such as octane) and 10% ethanol, C₂H₅OH, made from Queensland sugarcane. Both are organic compounds.
| Fuel | Energy released per litre (MJ) |
|---|---|
| Ethanol | 23.4 |
| Petrol | 34.2 |
| E10 |
Source: typical energy values (higher heating value) for petrol and ethanol.
4. Calculate the energy released when 1 L of E10 burns, and write it in Table 1.
Answer MJ
5. A driver changes from petrol to E10 and notices the car travels slightly fewer kilometres on a full tank. Use your answer to explain why.
6. Ethanol (a fuel and a solvent in hand sanitiser), acetic acid (makes vinegar sour) and propanone (removes nail polish) all have short carbon backbones. Explain how three organic compounds can behave so differently, using the ideas of carbon backbone and functional group.