Science and Technology K–6 · Year 3

Soil in a jar: sand, silt and clay settle in layers

Science understanding: Earth and space sciences

Practical, model not builtLow risk

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The idea

Soil is a mixture of particles of different sizes, and larger particles sink through water faster, so shaking soil in water sorts it into visible layers.

What you need

1 clear straight-sided jar with lid, about 1 L
garden soil, about 1 cup (250 mL), from the school grounds (with permission)
water to fill the jar to 3 cm below the rim
1 teaspoon dishwashing liquid (helps clay disperse)
ruler in millimetres
timer or clock

How to do it

Put the cup of soil into the jar, which fills about a quarter of a 1 L jar, add water to 3 cm below the rim and the dishwashing liquid, then seal the lid.
Shake hard for two minutes so every lump breaks up.
Stand the jar still and start the timer, then measure the height of the water above the soil in centimetres and write it down: every settling time depends on it, and a cup of soil in a 1 L jar leaves about 8 cm.
After 1 minute mark the top of the settled layer on the jar with a marker: with 8 cm of water above the soil, 1 minute has brought down everything coarser than about 0.04 mm, which is the sand and the coarsest silt.
After 2 hours mark the new level: the band above the first mark is the rest of the silt, down to about 0.0035 mm in 8 cm of water.
After 2 days mark again: the fine layer on top is clay. Floating bits are organic matter.
Measure each layer's thickness in millimetres and work out each as a percentage of the total settled depth.
Repeat with soil from a second place (a garden bed and a bare sports field) and compare.

What you should see

Three bands form: the coarsest grains at the bottom within a minute, silt over the next hours, and clay that keeps the water cloudy for a day or more. For quartz grains (density 2,650 kg per cubic metre) in water at 20 degrees Celsius, Ferguson and Church's settling equation gives 23 mm per second for a 0.2 mm sand grain, 3.0 mm per second for a 0.06 mm grain and 0.0036 mm per second for a 0.002 mm clay particle. A cup of soil in a 1 L jar about 9.5 cm across lies about 3.5 cm deep and leaves about 8 cm of water above it, and those three grains fall 8 cm in 3.4 s, 27 s and 6.2 hours. So the 1-minute mark catches everything coarser than about 0.04 mm and the 2-hour mark everything coarser than about 0.0035 mm, and the finest clay, near 0.0007 mm, is what the two days are for. For fine grains the equation is Stokes' law; for coarse sand Stokes' law alone runs far too fast (for a 2 mm grain it gives 3.6 m per second, against about 0.2 m per second). The percentage of sand, silt and clay describes the soil, but the boundary this jar sorts at in a minute is about 0.04 mm, not the 0.063 mm sand-silt boundary, which would need a water column near 20 cm, and not the 0.02 mm boundary used in Australian soil survey, so the percentages do not match an Australian soil texture class directly.

What changes

What you change: where the soil came from
What you measure: thickness of each layer in millimetres
What you keep the same: soil volume
water volume
shaking time
jar shape

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

Soil is one substance called dirt.
Clay stays in the water because it dissolves (it is suspended, and settles given time).

Safety card

Low riskLearners carry it out

Hazards

soil may carry organisms

Controls

wash hands after handling soil
no soil from areas that may be contaminated

Note

Risk assessment before the lesson using Primary RiskAssess or the school's own template.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science and Technology K-6 Syllabus (2017), current, taught until 2026; code read from the syllabus document on 22 September 2026ST2-10ES-S ST2-1WS-S
Science and Technology K-6 Syllabus (2024), implemented from 2027; NESA's timeline is 2026 plan and prepare and 2027 start teaching, and schools may choose to implement it during 2026; code read from the outcomes page on 22 September 2026ST2-DAT-01
Australian Curriculum v9AC9S3U02AC9S3I03AC9S3I04

Sources

The pages the author read to write this activity.

All Concept Studio activities