Year 10 Science · Unit 2 · Lesson 10

Energy Changes in Reactions

Challenge Worksheet

Name

Date

Class

Learning Goals

Evaluate a sweeping claim about exothermic and endothermic reactions using scientific evidence.
Construct a balanced argument that identifies both the truth and the overstatement in a claim.
Apply knowledge of real-world reactions to support or refute an assertion.

Go Deeper

Evaluate the claim

Someone claims…

"Exothermic reactions are always useful, they release energy we can harness for heating, fuel, and industry. Endothermic reactions are the opposite: they absorb energy without producing anything useful, which makes them wasteful and something scientists should try to avoid. In a perfect world, all industrial processes would be exothermic."

(a) What part of this claim is supported by the science you have learned? Give at least TWO specific examples of useful exothermic reactions.

Challenge 2 marks

(b) What is misleading or missing from this claim? Identify at least TWO endothermic processes that are essential or useful, and explain what would happen if they did not occur.

Challenge 2 marks

(c) What evidence or extra information would you need to properly evaluate whether a reaction is "useful" or "wasteful"? Suggest TWO criteria a scientist might use.

Challenge 2 marks

Show What You Know

1. Thermal decomposition of limestone (CaCO₃ → CaO + CO₂) is a major industrial process used in cement manufacturing, which is vital for Australian construction. It is endothermic and requires large amounts of energy. Using the energy diagram concept, explain why this reaction is endothermic and suggest why industry still uses it despite the energy cost.

Challenge 4 marks

2. Some exothermic reactions, like explosives detonating or uncontrolled bushfires, are highly destructive. Does this change your evaluation of the claim? Explain using one sentence.

Challenge 2 marks

Wrap Up

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