Year 8 Science · Unit 3 · Lesson 13

Modelling Chemical Change

Challenge Worksheet

Name

Date

Class

Learning Goals

Explain why scientists use particle models to describe chemical reactions.
Communicate the purpose and limitations of scientific models to a non-expert audience.
Use sentence starters to construct a structured scientific explanation.

Go Deeper

Explain it to a Year 6 student

Imagine you are explaining to your Year 6 cousin why scientists draw pictures of atoms bouncing around to describe chemical reactions. Use the four sentence starters below to write a clear, scientifically accurate explanation. You can use everyday examples.

Starter 1: "The basic idea of a particle model is that it shows us..."

Starter 2: "A good example from everyday life that helps explain this is..."

Starter 3: "The reason scientists draw these models — instead of just writing word equations — is..."

Starter 4: "One thing people often get confused about with particle models is... but actually..."

Show What You Know

1. A student says: "Particle models are more useful than word equations because they show you exactly what is happening at the atomic level." Do you agree? Evaluate this claim, including at least one strength and one limitation of particle models.

Challenge 3 marks

2. In a chemical reaction, the total mass of the reactants always equals the total mass of the products. Explain why this is the case using the particle model — what is actually happening to the atoms that makes this law always true?

Challenge 3 marks

Wrap Up

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