Year 8 Science · Unit 3 · Lesson 14
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Learning Goals
Real-world context
The Nullarbor Plain in southern Australia is one of the world's largest limestone karst landscapes. The limestone was formed from ancient seabeds and is gradually dissolving as slightly acidic groundwater — enriched with CO₂ from the atmosphere — seeps through cracks in the rock. This process has created thousands of caves and sinkholes across the plain over millions of years, and it is ongoing today.
(a) Classify the change occurring in the Nullarbor limestone — physical or chemical? Write a word equation for the reaction: limestone (calcium carbonate) + carbonic acid → calcium bicarbonate + water.
(b) Predict one long-term consequence of this chemical change on the landscape of the Nullarbor Plain over the next 10 000 years. Explain the chemical reasoning behind your prediction.
Read the graph
Australian CO₂ Emissions by Sector (approximate, 2022)
Data: Australian Department of Climate Change, Energy, the Environment and Water (DCCEEW), 2023.
(a) Which sector is the largest contributor to Australian CO₂ emissions? Approximately how much greater is its share than the Buildings sector?
(b) Which two sectors involve the most obvious chemical changes? Explain what chemical change is occurring in each sector.
(c) If Australia wanted to reduce its total CO₂ emissions by targeting the top two sectors, predict what percentage reduction could be achieved. Describe one chemical change that would need to be reduced or replaced in each sector.
Wrap Up
In one sentence, what was the main idea of this lesson?