Year 8 Science · Unit 3 · Lesson 15
Challenge Worksheet
Learning Goals
Find the mistake
A student wrote this answer
"In our investigation of how temperature affects the reaction between vinegar and bicarb soda, I kept the temperature as my dependent variable and measured how fast the fizzing stopped as my independent variable. I only did one trial at each temperature, which is fine because science just needs one accurate measurement. My results showed that at 40°C, the CO₂ production was 5 mL — the same as the other temperatures — so I deleted this result because anomalies are always mistakes and should be removed from the data. My graph showed a trend, so I can conclude that temperature causes faster reactions. This means the atoms in the reactants were destroyed and completely new atoms were created in the products."
1. Identify all four scientific errors in the student's answer. Write the error number, the incorrect statement, and the correct scientific idea.
2. Rewrite the student's answer correctly in full. Your version should fix all four errors and use precise scientific vocabulary from Unit 3.
1. A scientist claims: "I measured the same result four times in a row, so my conclusion must be correct." Explain two distinct reasons why this reasoning is flawed, drawing on ideas from Unit 3.
2. Write a word equation for one chemical change that occurs in a human industrial system and one that occurs in a natural system. For each, state whether the reaction is exothermic or endothermic (releases or absorbs energy) and explain how you know.
Wrap Up
What was the most surprising thing you learned about chemical change in Unit 3?