Science and Technology K–6 · Year 3

Which soil holds the most water? Sand, clay and potting mix

Science understanding: Earth and space sciences

PracticalMedium risk

School laboratory, not for home

In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

The idea

Different soils hold and drain water differently because of particle size, and the difference can be measured in millilitres.

Safety card

Medium riskA teacher supervises

Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

Hazards

soil organisms
potting mix dust, which can carry Legionella longbeachae (the warning is printed on the bag)

Controls

the adult opens the potting mix bag outdoors, away from faces, and weighs the dry mix outdoors, pouring gently to keep dust down
a P2 or N95 mask and gloves for everyone handling soil or potting mix, the protection NSW Health names for potting mix: this test needs the mix dry, so wetting it down, the control that suppresses the dust, cannot be used, and the mask carries the load instead
the funnels are filled outdoors or at an open window, with the mix poured rather than dropped, and carried inside only once the water has been added
an adult supervises every step that moves dry mix, and the dry mix is not handled by learners who have a respiratory condition
wash hands

Note

Risk assessment before the lesson using Primary RiskAssess or the school's own template. The potting mix controls follow the NSW Health Legionnaires' disease fact sheet, read on 23 September 2026, which names wetting the mix down, gloves and a P2 or N95 mask.

What you need

3 large funnels with coffee filter papers, and 3 more filter papers for the repeat
3 measuring cylinders or jugs marked in millilitres (250 mL)
200 g each of dry washed sand, dry clay soil (crumbled) and dry potting mix, weighed on a kitchen balance (100 g of each for each of the two runs)
about 700 mL water in a measuring jug (100 mL for each soil in each run, plus water to wet the filters)
a P2 or N95 mask and gloves for everyone handling the soils
timer

How to do it

Set a filter paper in each funnel, wet it and let it drain so the paper does not count as held water, then empty the cylinders and stand each funnel in one.
Put 100 g of one soil into each funnel; do not press it down. Dry potting mix is bulky, so check before the lesson that 100 g of it fits in the funnel with room for 100 mL of water above it, and use a larger funnel if it does not.
Pour exactly 100 mL of water slowly onto each soil at the same time and start the timer.
Read the drained volume in each cylinder at 1, 2, 5 and 10 minutes and record it in a table.
Water held = 100 mL minus the volume drained at 10 minutes.
Draw a column graph of water held for the three soils.
Repeat once more with fresh dry soil and fresh filter papers (wet soil cannot be reused as dry soil) and use the mean of the two runs.

What you should see

Sand drains fastest and holds least; clay soil drains slowest, and clay soil and potting mix hold more than sand. Water held is worked out by difference (100 mL minus the drained volume), so water left clinging to the funnel counts as held. Very dry potting mix can repel water at first, letting some run straight through. The order of the three soils, taken from the mean of the learner's two runs, is the result; no published figure applies to these particular soils.

What changes

What you change: type of soil
What you measure: volume of water drained after 10 minutes (mL)
What you keep the same: soil mass 100 g
water volume 100 mL
funnel and filter
pouring rate

Common misconceptions

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

The soil that drains fastest is the best for plants.
Water disappears into soil; it does not stay there (the mass balance shows it does).

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 v9AC9S3U02AC9S3I02AC9S3I04AC9S3I05

Sources

The pages the author read to write this activity.

All Concept Studio activities