Year 8 Science · Unit 3 · Lesson 2
Challenge Worksheet
Learning Goals
Explain it to a Year 5 student
A younger student is confused: "Both dissolving sugar and baking a cake use water and heat — so why is one physical and the other chemical?" Use the sentence starters below to explain clearly. You can use everyday examples from your own experience.
Starter 1: "The basic difference between dissolving and baking is..."
Starter 2: "When sugar dissolves, the particles..."
Starter 3: "When a cake bakes, the particles..."
Starter 4: "The best way to prove which type of change it is would be to..."
1. CSIRO food scientists study the Maillard reaction — the chemical change that browns bread and creates new flavour compounds. If this reaction is chemical, why can you still separate the bread back into parts by tasting individual ingredients? Is this separation evidence it was physical? Explain.
2. A student makes this claim: "Dissolving must be chemical because you can't see the sugar anymore — it has disappeared and formed something new." Write a precise scientific rebuttal (disagreement) of this claim, using particle-level language and a recovery test as evidence.
Wrap Up
In one sentence, what was the main idea of this lesson?