What it shows
Plant roots hold soil together. When water is poured on, bare soil washes away much faster than soil covered with grass or dead leaves.
This idea has a short entry only. For the science behind it, read the sentence above with your textbook and ask your teacher to explain the law or idea it shows, so you can describe it in your own words.
Materials
- Three plastic bottles cut lengthwise
- Soil, grass seedlings and dry leaves
- Three cups to collect the run-off
- Water in a mug
Safety
For this project: An adult should cut the bottles. Wash your hands after handling soil.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
How to go about it
Numbered steps have not been written for this idea yet. Plan it with your teacher: sketch the design with measurements, build one part at a time, test each part, and write every observation with the date. The free ebooks below have step-by-step projects of the same kind.
Take it further
Compare how muddy the water in each cup is, and how much soil settles at the bottom.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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