Teacher sheet · Ages 10–11 · about 45–50 minutes
Soil: sand, silt, clay and layers
Lesson page: echoesof.science/school/soil/ages-10-11/ · Pupil worksheet: echoesof.science/school/soil/ages-10-11/print/
Learning aims
- Soil is a mix of minerals, organic matter, air and water.
- Sand, silt and clay are grains of different sizes.
- Particle size affects how fast water drains.
- Soils have layers (horizons) and form very slowly.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: why do puddles stay on some fields and not others? |
| 10 min | Read the text; feel dry sand and damp clay (rub between fingers). |
| 20 min | Drainage fair test in groups; record in the table. |
| 5 min | Which soil layer? game. |
| 5 min | Quiz. |
| 5 min | Worksheet questions. |
Materials for the experiment
- Three clear plastic cups with a few small holes poked in the bottom (by an adult)
- Three more cups to catch the water
- Sand, clay-rich soil and garden compost (or loam)
- A measuring jug and water
- A stopwatch
- Coffee filters or kitchen paper
Safety: An adult makes the holes in the cups. Use clean bought sand and compost or soil from a clean place, never where pets go. Wear gloves if you like and wash hands afterwards. Mop up spills.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| Soil is solid all the way through. | About half of a typical soil is pore space filled with air and water. |
| Clay soil is dry because water doesn't go in. | Clay holds water well; it is the drainage that is slow. |
| All soil is the same as the topsoil. | Soils have layers: topsoil, subsoil and broken rock all differ. |
Worksheet answers
- Minerals about 45%, organic matter about 5%, air about 25%, water about 25%.
- Usually sand, because it has the largest spaces (pores) between its grains, so water flows through quickly.
- A labelled drawing: O leaves at the top, A dark topsoil, B subsoil, C broken rock, bedrock below.
- Good: plants have water for longer. Bad: it drains slowly, so it can become waterlogged or puddly.
Quiz answers
- Roughly how much of a typical soil is air and water together? About half. A typical soil is about 25% air and 25% water.[1]
- Which particles are the smallest? Clay. Clay particles are smaller than 0.002 mm.[1]
- Why does water drain quickly through sand? There are big spaces between the grains. Large pores let water through fast.[8]
- In which horizon do most plant roots grow? A (topsoil). The A horizon is the main layer for root growth.[1]
- What is humus? Rotted plant and animal matter in soil. Humus is the organic material of soil.[2]
- In the drainage test, what should you change? Only the type of soil. Change one thing, keep the rest the same: that is a fair test.[8]
Going further
Do the jar test: half fill a jar with soil, add water, shake and leave for a day. Measure the layers that settle and compare soils from two places.
Sources used in this lesson
- [1] Soil basics (University of Illinois Extension): reliability High
- [2] Biology 2e, 31.2 The Soil (OpenStax (Rice University)): reliability High
- [3] Polluting our soils is polluting our future (Food and Agriculture Organization of the United Nations (FAO)): reliability High
- [6] Earthworms (Royal Horticultural Society (RHS)): reliability High
- [7] Microorganisms and soil processes (Ontario Ministry of Agriculture, Food and Agribusiness): reliability High
- [8] Soil texture and infiltration (RAINSS lesson) (American Geosciences Institute): reliability High
Full list with links and a note on each source's reliability: echoesof.science/school/soil/sources/
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