Science and Technology K–6 · Year 4

Mini greenhouse: designing a home for a salad crop

Science understanding: Earth and space sciences; Living World food and fibre (NSW 2017 Stage 2)

PracticalLow risk

The idea

A sealed clear container keeps seeds warm and damp because water that evaporates condenses on the lid and runs back down, so a designed environment can supply what a food plant needs to germinate and grow.

What you need

5 clear plastic cups of about 300 mL
cotton wool
20 rocket seeds (a salad crop)
a 10 mL syringe or measuring spoon for water
sticky tape
2 small thermometers
a ruler in millimetres
a bright windowsill out of hot afternoon sun

How to do it

Line the bottom of two cups with cotton wool, wet each with 10 mL of water and sprinkle 5 seeds on each.
Make the greenhouse: turn a third cup upside down on top of one planted cup and seal the join with tape. Leave the other planted cup open as the control.
Make a thermometer pair: a sealed pair of cups with a thermometer inside and a thermometer beside it on the sill, to compare inside and outside air.
Every day for 10 days, at the same time, record: droplets on the lid, whether each cotton wool is wet or dry (add no more water to either), the number of seeds germinated, the height of the tallest seedling, and both temperatures.
Graph germinated seeds and seedling height against day for the two planted cups.
Change one thing in the design (for example a vent hole in the lid or a shaded position), retest and compare.
Explain how a farm greenhouse helps grow food, using your results.

What you should see

Within a few hours on the sill the inside of the greenhouse lid mists over and droplets run back onto the cotton wool: water evaporates from the damp cotton and condenses on the cooler lid, the water cycle in a cup. The open cup's cotton wool dries out within a few days, so its seeds may not germinate or its seedlings wilt, while the sealed cup stays damp for the whole 10 days with no water added. In sunlight the air inside the sealed cups reads warmer than the air beside them; in strong direct sun it can overheat, which is why real greenhouses have vents. The germination counts and heights are the learner's data; the finding is that the enclosed design keeps its water and grows healthier seedlings than the open cup.

What changes

What you change: sealed greenhouse or open cup (then one design change)
What you measure: cotton wool dampness, seeds germinated, seedling height, inside temperature
What you keep the same: water added at the start
seed type and number
cup size
position on the sill

Common misconceptions

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

A sealed plant will run out of water in a day.
Seeds need soil before they can germinate.
A greenhouse makes new water (it keeps the same water cycling).

Safety card

Low riskLearners carry it out

Hazards

mould on damp cotton wool
sprouted seeds can carry bacteria

Controls

seedlings and sprouts are not eaten
mouldy cups thrown away with the lid still taped
wash hands after handling

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 2026ST2-5LW-T ST2-2DP-T
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-DDT-01 ST2-DAT-01
Australian Curriculum v9AC9S4U02AC9S4H02AC9S4I03AC9S4I04

Sources

The pages the author read to write this activity.

All Concept Studio activities