Year 9 Science · Unit 2 · Lesson 05

Organic and Inorganic Compounds

Challenge Worksheet

Name

Date

Class

Learning Goals

Design a controlled investigation to test whether an unknown compound is organic or inorganic.
Critically evaluate the claim that "natural = organic" and "synthetic = inorganic".
Use specific chemical examples to refute or support scientific claims.

Go Deeper

Design a mini-experiment

A scientist at CSIRO wants to test: "Can you tell whether an unknown white powder is an organic or inorganic compound using simple laboratory tests?" Two suggested tests are a combustion test (heat the powder and observe whether it burns or chars) and a solubility test (dissolve the powder in water and observe). Plan the investigation below using at least these two tests.

What I will change (independent variable)
What I will keep the same (controlled variables, list at least 3)
What I will measure or observe (dependent variable)
My prediction, what results would indicate an organic compound?
How I would know if my prediction is wrong (falsification)
One limitation of this experiment

Think carefully: could an organic compound fail the combustion test? Could an inorganic compound dissolve well in water? Consider glucose (organic, dissolves in water) and NaCl (inorganic, also dissolves in water). What does this mean for your test design?

Show What You Know

1. A science vlogger with 2 million subscribers posts: "All natural materials are organic compounds and all synthetic (human-made) materials are inorganic compounds. So anything natural is organic and anything synthetic is inorganic. That's why natural products are always safer, they're made of completely different chemistry from synthetic ones."

Using specific named chemical examples from this lesson, refute or support each part of this claim. Your answer should address: (i) whether natural materials are always organic; (ii) whether synthetic materials are always inorganic; (iii) whether the conclusion that natural = safer is chemically justified.

Challenge 4 marks

2. Your combustion test in the Go Deeper activity gives a positive result (the powder burns and produces black char). However, a classmate argues this single test is not sufficient to definitively classify the compound as organic. Evaluate this argument. Is the classmate correct? Explain what additional evidence you would need, and identify a specific compound that might give an ambiguous result in your test.

Challenge 3 marks

Wrap Up

In one sentence, what was the main idea of this lesson?