Presence of minerals in soil

Class: 6ème

Lesson: La nutrition des plantes

Rationale: Demonstrate the presence of minerals in the soil by filtering soil and drying the filtrate.

Materials:

sugar box

pen

candles

matches

glass bowl

soil (as rich as possible)

raw cotton material (available in any magasin for ~400 CFA/meter)

water

glasses

Procedure:

Preparation at least 3 days before the class:

1. Draw a circle, the diameter of a glass, in the bottom of a sugar box.

2. With a pen, poke holes within the circle.

3. Seal the inside of the box with melted candle wax.

4. Lay a piece of material, just bigger than the box, in the filter. This is to prevent the soil from washing through.

5. Add about a half glass of dry soil to the filter. Damp soil doesn't filter well.

6. Put the filter over a glass.

7. Add a glass of water and catch the filtrate. It should be cloudy but not muddy.

8. Put the filtrate in a clear glass bowl and dry in the sun for one or two days.

In class:

9. Repeat the experiment and at the end show the dried filtrate in the bowl that was prepared in advance. Explain that the dried white substance in the bowl are minerals.

Source: Filter design, B. Cole; HBJ Concepts in Science Orange, p. 196; Green, p. 181.