Science and Technology K–6 · Year 1

Do seeds need air: germinating under water and on damp cotton wool

Living World (NSW 2017); Science understanding, Biological sciences (ACARA v9)

PracticalLow risk

The idea

A seed needs water and air together: seeds on damp cotton wool grow roots, the same seeds held under still water swell and rot, and dry seeds do nothing at all.

Safety card

Low riskAn adult supervises

Hazards

Rotting seed in standing water grows bacteria and mould
Garden seed can be sold treated with fungicide
Small seeds are a choking risk for the youngest learners

Controls

Untreated seed only, with the packet read by the adult before the lesson
The under-water jar opened and emptied outdoors by the adult at the end, with no one leaning in to smell it
No seed goes near a mouth, and hands are washed after every count
All three jars emptied into the garden and washed at the end of the 10 days

Note

No laboratory reagents and no heat; the hazards to control are standing water and mould, so the NSW Department of Education science safety and compliance page applies. Record the activity on Primary School RiskAssess (riskassess.com.au).

What you need

60 untreated radish or cress seeds from one packet, 20 per jar
3 clear jars or takeaway containers of the same size, labelled damp, under water and dry
Cotton wool, enough for a 2 cm layer in the damp jar and the same in the dry jar
Tap water: 20 mL for the damp jar, and enough in the under-water jar to stand 3 cm above the seeds
A permanent marker, and a wall chart with a row per jar and 10 dated columns
A hand lens
A jug for topping up, and a tray to stand all three jars on

How to do it

Count 20 seeds into each of the three jars, saying the count aloud as a class so every jar starts the same.
Damp jar: lay the seeds on wet cotton wool and add 20 mL of water, enough to wet the cotton wool without covering the seeds.
Under-water jar: lay the seeds in the bottom and pour water until it stands 3 cm above them. Leave the water still from then on, because stirring carries air down into it.
Dry jar: lay the seeds on dry cotton wool and add nothing.
Stand the three jars side by side on the tray, out of direct sun, and write down a prediction for each jar before any counting starts.
On each school day, count the seeds in each jar that show a white root and record the three counts on the chart. Keep the damp cotton wool damp and top the under-water jar back to 3 cm, pouring gently down the side.
Keep counting for 10 school days, then draw one bar per jar of the final count out of 20.
Compare the bars with the predictions, then set the whole test up a second time to see whether the same pattern comes back.

What you should see

The damp jar is the only one with roots that keep growing, and its daily count climbs. The dry jar stays on zero for all 10 days, because dry seed keeps. The under-water jar is the one to watch closely and the honest result is rarely a clean zero: still water holds a little dissolved air, so a few seeds swell, split and push out a short root that then stops and browns, while the water turns cloudy and smells by the second week. The finding is therefore far fewer roots under water, and none that carry on growing. Chance matters and can be worked out: with 20 seeds in a jar one seed is 5 percentage points, and when about half of a jar's seeds germinate, two jars treated alike differ by chance with a standard deviation of 3.2 seeds, the square root of 2 x 20 x 0.5 x 0.5, so a gap of up to about 6 seeds proves nothing on its own, while 18 against 2 is far beyond chance. A class result of 18 out of 20 on the damp cotton wool is 90 per cent against a low single figure under water and 0 dry. The learner knows it worked when the damp bar towers over the other two and the dry bar is empty.

What changes

What you change: what the seeds are given (damp cotton wool with air around them, still water 3 cm over the top, dry cotton wool)
What you measure: the number of seeds out of 20 with a visible white root, counted each school day
What you keep the same: 20 seeds from the same packet in every jar
the same jars, side by side on one tray, out of direct sun
the same room temperature for all three
the water topped up gently and never stirred

Common misconceptions

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

Seeds need only water, so more water is always better.
A seed under water has the most water of all, so it should grow best.
The seeds in the dry jar are dead.
The dry jar shows nothing, so it does not count as part of the test.
Seeds need soil before they can start to grow.

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), NESA. Current syllabus; NESA's timeline is 2026 plan and prepare, 2027 start teaching the 2024 syllabus. Code read from the official syllabus document on 2026-09-22.ST1-4LW-S ST1-1WS-S
Science and Technology K-6 Syllabus (2024), NESA. Implementation from 2027, so this code describes the future syllabus. Code read from the outcomes page on 2026-09-22.ST1-SCI-01 ST1-PQU-01 ST1-DAT-01
Australian Curriculum v9AC9S1U01AC9S1I01AC9S1I02AC9S1I03AC9S1I04AC9S1I05AC9S1I06

Sources

The pages the author read to write this activity.

All Concept Studio activities