You will be challenged to place three ‘ocean’ samples on a map based on their chemical properties.

Activity steps

1. Collect your samples.
2. Use a pipette to put a few drops of your first sample on the spotting tile.
3. Add one drop of the Universal Indicator.
4. Use pH chart to find the pH, and record this in your book.
5. Use the mass balance to find the mass of your evaporating basin.
6. Pour your first sample into the evaporating basin.
7. Heat the solution over a medium flame to evaporate the water.
8. Allow the basin to cool.
9. Use the mass balance to find the mass of the evaporating basin with the salt residue inside.
10. Find the mass of the salt residue.
11. Find the concentration of salt in the sample.
12. Repeat this for the other ocean samples.

• Three ‘ocean’ samples (glasses with 50 ml with water of various degrees of acidity and salinity) labelled: Sample A (pH 8.1, salinity 40 g/litre), Sample B (pH 8.4, salinity 31 g/litre), Sample C (pH 8.2, salinity 30 g/litre)
• 3 x pipettes
• Spotting tile
• Universal indicator
• pH chart
• 2 x evaporating basins
• Bunsen burner
• Tripod and gauze
• Mass balance
• Eye protection

Expected results

You should find that sample A is the Indian Ocean (with 2 g mass of salt residue), sample B is the Northern Pacific (1.55 g mass of residue) and sample C is the Southern Ocean (1.6 g mass of residue).