Year 7 Science · Unit 2 · Lesson 7
Challenge Worksheet
Learning Goals
Explain it to a Year 5 student
Imagine your younger cousin has just said, "Water must be a mixture — it's made of hydrogen AND oxygen, so there are two different things in it!" Use the sentence starters below to explain why water is actually a compound, not a mixture. Use real examples from everyday life to help.
Starter 1: "The basic idea of a compound is..."
Starter 2: "A mixture is different because..."
Starter 3: "In water, the hydrogen and oxygen atoms are..."
Starter 4: "The reason people often confuse compounds and mixtures is..."
1. A student claims: "If I mix hydrogen gas and oxygen gas in a container, I've made water." Identify what is wrong with this claim and explain what would actually need to happen to make water from hydrogen and oxygen.
2. Table salt (NaCl) is safe to eat, even though sodium catches fire in water and chlorine is a poisonous gas. Explain what this tells us about the properties of a compound compared to the elements it is made from. Use the word "bonded" in your answer.
Wrap Up
In one sentence, what was the main idea of this lesson?