Year 8 Science · Unit 3 · Lesson 5
Apply Worksheet
Learning Goals
Real-world context — Australian barbecue
It's a Sunday afternoon in suburban Brisbane. The family sets up a charcoal barbecue in the backyard. As the coals heat up, smoke and CO₂ drift into the air. Sausages sizzle as fat drips onto the hot coals, causing small flares. A corn cob steams in aluminium foil. Ice in a drink cooler slowly melts in the 32°C heat. Marinade on chicken caramelises and turns brown on the grill. A spilled soft drink evaporates quickly on the hot concrete. All of this happens within about 30 minutes.
(a) Identify at least three physical changes happening at the barbecue. For each, state which lesson 1–4 concept explains why it is physical (e.g. particle model, reversibility, no new substance).
(b) Identify at least two chemical changes and state the observable evidence for each (colour change, gas produced, temperature change, precipitate, light/sound).
Because… chain — synthesis across lessons 1–4
Fill in the missing effects to complete the causal chain about cooking a sausage on a BBQ. Draw on all four lessons.
Overall classification and reason:
1. A student says "everything that happens at a BBQ is a chemical change because it all involves heat." Using specific examples from the scenario above, explain why this is wrong.
2. Charcoal burning at the BBQ produces CO₂. Describe how you would test the gas rising from the coals to confirm it is CO₂. Include the test used, the equipment needed, and the expected result.
Wrap Up
In one sentence, what was the main idea of this unit?