For this activity you will need:
- 1 large (500-ml), clear plastic container or cup
- 1 coffee filter
- 1 rubber band
- 200 cc of soil
- 25 cc of salt
- 250 ml of water
When the water has evaporated (this will take a few days), what is left
behind? Why do you think salt can pass through the filter while most of
the soil is left behind? Why did we use a filter in the experiment? Relate
this activity to what happens when irrigation water from fields is disposed
of in evaporation ponds.
- Place the coffee filter in the coffee cup and fold the edge over
the rim to form a pocket inside the cup.
- Use the rubber band to secure the folded edge of the coffee filter
to the cup. Put the soil into the filter.
- Mix the salt with the soil.
- Slowly pour the water on the soil, wetting it thoroughly, and wait
for it to drain down.
- When the water has stopped draining, dispose of the wet filter and
- Place the cup on a sunny windowsill to allow the water to evaporate.
Return to Clue #2.