Science 7–10 · Year 10

Albedo: how ice, sand, soil and water take up sunlight

Science understanding: Earth and space sciences (NSW Stage 5 focus area: Environmental sustainability)

PracticalLow risk

The idea

Light surfaces such as ice and snow reflect most sunlight while dark land and water absorb it, so when ice melts and exposes darker ground or sea, Earth absorbs more energy and warms further.

What you need

4 identical 9 cm Petri dishes filled level to 1 cm depth with dry white sand, dry dark garden soil, tap water, and fresh green grass clippings
4 thermometers or temperature probes, each tip 2 mm below the surface (just under the surface for water)
1 lamp with a 150 W R125 infrared heat globe in place of the UCAR activity's 100 to 150 W incandescent bulb, which is no longer sold in Australia, 30 cm above the dishes, or direct midday sun
an A4 colour print of a glacier with white ice, dark rock and meltwater (the UCAR activity uses a Bhutan glacier photograph) and 2 more thermometers taped under a white and a dark area
2 ice cubes of equal mass, one on white card and one on black card

How to do it

Record the starting temperature of every dish and of the two photograph thermometers in shade.
Switch on the lamp and read every thermometer every 2 minutes for 10 minutes.
Repeat with the glacier photograph under the lamp, reading every 2 minutes for 8 minutes.
Put the two ice cubes under the lamp and time how long each takes to melt completely.
Rank the surfaces by temperature rise and compare the ranking with the albedo ranges UCAR gives.
Run the whole set three times and use the mean rise for each surface.

What you should see

Among the dry surfaces the dark soil warms most and the white sand least; the thermometer under the dark rock of the glacier photograph rises more than the one under white ice; the cube on black card melts first. Water warms slowly although it absorbs strongly, because of its high heat capacity: a variable to discuss, not an albedo effect. UCAR gives ice and snow reflecting 80 to 90 percent of sunlight and dark land 10 to 20 percent, so a dark surface absorbs 80 to 90 percent against 10 to 20 percent for snow, four to nine times as much energy per square metre. The learner knows it worked when the ranking repeats in all three runs.

What changes

What you change: surface type and colour
What you measure: temperature rise in 10 minutes; ice melting time
What you keep the same: lamp power and distance
depth of material
probe depth
starting temperature
time

Common misconceptions

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

Dark colours attract heat; they absorb more of the incoming light and turn it into heat, while light colours reflect it.
Melting sea ice makes no difference because it was already in the sea; it barely changes sea level but replaces a bright surface with dark water that absorbs more sunlight.

Safety card

Low riskLearners carry it out

Hazards

hot lamp and globe: an infrared heat globe runs hotter than a lighting globe and can scorch paper it is close to
microorganisms in garden soil

Controls

do not touch the lamp; keep it 30 cm clear of the dishes and of the glacier print, and let it cool before moving it
use garden soil rather than potting mix, handle it with gloves and wash hands afterwards

Note

No hazardous chemical and no flame: a generic classroom risk assessment (CSIS 1.7 or RiskAssess) covers trips, spills, radiant lamps and sharp edges.

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 7-10 Syllabus (2023), NSW Education Standards Authority (implemented from 2026; codes read at curriculum.nsw.edu.au on 22 and 23 September 2026)SC5-ENV-01 SC5-WS-04 SC5-WS-06
Australian Curriculum v9AC9S10U04AC9S10I02AC9S10I03

Sources

The pages the author read to write this activity.

All Concept Studio activities