Science and Technology K–6 · Year 5

Leaf shape and water loss: flat leaf, rolled leaf, waxy leaf

Science understanding: Biological sciences

PracticalLow risk

The idea

Plants in dry habitats have small, rolled or waxy leaves because water loss depends on the surface exposed to air, which a learner can show with paper leaves of equal mass and a balance.

What you need

3 identical 10 cm x 10 cm squares of paper towel
water in a spray bottle
a balance reading to 0.01 g, such as a jeweller's pocket scale (a kitchen balance reading to 0.1 g can compare only the mass lost over the whole hour)
a paper clip and a strip of cling film
3 wire hooks or pegs on a line in the same room
timer

How to do it

Wet each square evenly with the same number of sprays (about 10) and weigh it. Adjust with a spray or a blot until all three are within 0.1 g.
Leave square A flat and hang it. Roll square B into a tight cylinder 10 cm long and about 1 cm across, clip it and hang it. Wrap square C flat in cling film on one side only (a waxy upper surface) and hang it.
Weigh all three every 10 minutes for an hour and record the mass. In still indoor air the rolled leaf can lose less than 0.1 g in 10 minutes, so with a 0.1 g balance compare the mass each leaf lost over the whole hour instead.
Graph mass against time for the three leaves.
Work out the exposed area of each: the flat leaf has two 100 cm2 faces (200 cm2), the rolled cylinder about 31 cm2 of outer surface, the half-wrapped leaf 100 cm2.
Compare the rate of mass loss with the exposed area and relate the shapes to spinifex, eucalypt and rainforest leaves.

What you should see

The flat leaf dries fastest, the half-wrapped leaf at about half that rate, and the rolled leaf slowest. Exposed area computed from the geometry is 200 cm2 for the flat leaf and 31.4 cm2 for a 10 cm cylinder of 1 cm diameter (pi x 1 x 10), a ratio of 6.4, so the exposed area predicts the flat leaf loses water several times faster than the rolled one at first for the same mass of water. With a 0.01 g balance the graph slopes give the rates in grams per minute; with a 0.1 g balance many 10-minute readings of the rolled and half-wrapped leaves do not change, and the mass lost over the whole hour is the comparison.

What changes

What you change: leaf shape or covering
What you measure: mass lost per 10 minutes
What you keep the same: paper size
starting water mass
position and draughts
time

Common misconceptions

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

Desert plants have small leaves because there is less food for them.
Waxy leaves are waxy to look shiny.
Plants lose water only when they are cut.

Safety card

Low riskLearners carry it out

Hazards

cling film over the nose or mouth is a suffocation risk
sprayed water on the floor is a slip hazard

Controls

cling film kept away from faces
spray only over a tray
wipe up drips at once

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 2026ST3-4LW-S ST3-1WS-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; Stage 3 content: 'Observe behavioural and structural adaptations of plants and animals, and suggest how these may help them survive in their environments', which sits in the focus area whose knowledge outcome is this one; code read from the outcomes page and the content read from the Stage 3 content page on 23 September 2026ST3-SCI-01
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 2026ST3-PQU-01 ST3-DAT-01
Australian Curriculum v9AC9S5U01AC9S5I02AC9S5I03AC9S5I04

Sources

The pages the author read to write this activity.

All Concept Studio activities