Year 8 Science · Unit 3 · Lesson 9
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Learning Goals
Because… chain
Fill in the missing effects. Each cause leads to the next step in bread-making.
Overall outcome (describe the bread produced):
Scenario
A student sets up two covered jars. Jar A contains a lit candle; Jar B contains a small piece of iron wool moistened with water. After a week, the candle in Jar A has gone out and the iron in Jar B has turned orange-red. The student records these observations and tries to explain what happened.
(a) Identify the chemical reaction occurring in each jar. Name the reactants and products for each reaction, and state one observable sign of chemical change visible in each jar.
(b) Both reactions in the jars involve a gas from the air. Which gas is it, and what do these two reactions have in common in the way they use this gas? Use what you know from the lesson to explain why the gas eventually runs out in each sealed jar.
1. Explain why photosynthesis and cellular respiration are considered opposite reactions. Include the reactants and products of each in your answer.
2. A student claims that "melting butter on toast is a chemical reaction because it looks different." Identify two pieces of evidence you would look for to decide whether a change is chemical, and explain why butter melting does NOT meet these criteria.
Wrap Up
In one sentence, what was the main idea of this lesson?