Year 7 Science · Unit 2 · Lesson 20

Unit 2 Synthesis

Challenge Worksheet

Name

Date

Class

Learning Goals

Identify scientific errors spanning multiple Unit 2 topics — atoms, mixtures, chemical change and the periodic table.
Correct misconceptions with precise scientific language.
Synthesise knowledge from across the full unit to evaluate a student's written response.

Go Deeper

Find the mistakes

A student wrote this Unit 2 summary

"In Unit 2, I learned that all matter is made of atoms. An atom's atomic number tells you how many protons AND neutrons are in the nucleus. Elements and mixtures are both pure substances, but mixtures can be separated by physical means. When iron rusts, a new substance (iron oxide) is formed, which makes rusting a physical change. In the periodic table, elements in the same column have the same number of electron shells, which gives them similar chemical properties."

(a) Find all four errors in the student's summary. For each one, identify the topic it relates to and write the correct version.

Challenge 4 marks

(b) Choose two of the errors you found. For each one, explain why this mistake is easy for a Year 7 student to make — what is the common confusion behind it?

Challenge 2 marks

Show What You Know

1. A substance has a fixed boiling point of 100 °C, is made of molecules containing two hydrogen atoms bonded to one oxygen atom, and cannot be separated into simpler substances by physical means. Classify this substance fully — is it an element, compound, or mixture? Explain using at least three Unit 2 concepts.

Challenge 3 marks

2. A student dissolves copper sulfate in water to make a blue solution, then heats it until all the water evaporates and a blue solid remains. Using Unit 2 vocabulary, explain at the particle level what happened at each stage. Was either stage a chemical change? How do you know?

Challenge 4 marks

Wrap Up

What surprised you most in Unit 2? Why?