Year 7 Science · Unit 2 · Lesson 8
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Learning Goals
Order the steps
Number the steps from 1 to 7 to show the correct order for filtering sand from water. Step 1 = what you do first.
| Order | Step |
|---|---|
| Wait for the water (filtrate) to drip through into the flask below. | |
| Fold the filter paper into a cone shape. | |
| Pour the sandy water down a glass stirring rod into the funnel — do not pour directly. | |
| Place the filter paper cone inside the funnel. | |
| Rinse the sand residue with a small amount of clean water. | |
| Set the funnel on top of the conical flask. | |
| Put on safety glasses before starting. |
Real-world context
Lake Eyre (Kati Thanda) in South Australia is one of the largest salt lakes in the world. For most of the year it is a vast, dry salt flat — but when rainfall fills it, it becomes a shallow brine lake. As the sun heats the shallow water over weeks and months, the water evaporates, leaving behind a thick white crust of sodium chloride (NaCl) and other salts. The same process is used commercially at the Coorong Salt Works in South Australia, which produces thousands of tonnes of table salt annually using solar evaporation ponds.
(a) Explain how evaporation works as a separation technique. Use the Lake Eyre example to help you describe what happens to the water and the salt.
(b) The Coorong Salt Works uses sunlight and wind instead of a Bunsen burner. Identify the physical property difference that makes this separation possible, and explain why it does NOT require any chemical change.
1. A student has a beaker containing salt, sand and water. Describe a sequence of two separation steps they could use to obtain a sample of pure sand AND a sample of pure salt. State what method is used at each step and what it removes.
2. Name one safety rule you must follow during evaporation and explain the reason for it.
Wrap Up
In one sentence, what was the main idea of this lesson?