Year 9 Science · Unit 2 · Lesson 05
Apply Worksheet
Learning Goals
Order the steps
Number the steps from 1 to 6 to show the correct order for deciding whether a compound is organic. Step 1 = what you do first.
| Order | Step |
|---|---|
| If C–H bonds are present, classify the compound as organic. | |
| Write down or look up the molecular formula of the compound. | |
| If carbon (C) is present, check whether hydrogen (H) atoms are also in the formula. | |
| If the formula contains no carbon at all, classify the compound immediately as inorganic. | |
| If carbon is present but hydrogen is absent (e.g. CO₂ or CaCO₃), apply the chemistry rule: no C–H bond means inorganic. | |
| Look at the formula and identify whether the element carbon (C) appears. |
Read the graph
The bar chart below compares the melting points of four organic compounds and four inorganic compounds. Study it carefully, then answer the questions.
Data: Haynes, W.M. (ed.) CRC Handbook of Chemistry and Physics, 96th Edition (2015), CRC Press.
(a) Describe the pattern you can see when comparing the melting points of organic compounds to inorganic compounds in the graph.
(b) Using the graph, identify which organic compound has the highest melting point. Suggest one reason why its melting point is higher than the other organic compounds shown (consider molecule size and complexity).
(c) NaCl has a melting point of 801°C while wax (a mixture of organic hydrocarbons) melts around 50–60°C. Explain why NaCl is a more suitable fireproofing additive than wax, using the melting point data to support your answer.
1. A student is given an unknown compound with the formula C₈H₁₈. Using the step-by-step classification method practised in the Warm Up, show how you would determine whether this compound is organic or inorganic. State your final classification.
2. Australian E10 petrol blends 90% octane (C₈H₁₈) with 10% ethanol (C₂H₅OH) made from Queensland sugarcane. Both components are organic compounds. Suggest two properties that both compounds share because they are organic, and explain how those properties make them useful as fuels.
Wrap Up
In one sentence, what was the main idea of this lesson?