Water as a Medium

STEP 1

Buoyancy

Compare the support an organism receives in air and in water.

☁️

Air

Low density

↓ Weight

Little buoyant support

💧

Water

Much higher density

Drop loon here

↑ Buoyant force

Greater buoyant support

STEP 2

Viscosity

Compare movement through air and water, two fluids with very different resistance to motion.

☁️

Air

Lower viscosity

Example speed 0.0 m/s

💧

Water

Higher viscosity

Measured underwater speed 0.00 m/s

Actual speed also depends on how the loon is adapted to fly or swim. The important physical difference here is that water offers much greater resistance to movement than air.

STEP 3

Thermal conductivity

Release the same thermal-energy pulse from a seal in air and in water.

☁️

Air

Low thermal conductivity

≈ 0.026 W m⁻¹ K⁻¹

37°C

Heat transfer rate

Slow heat transfer

💧

Water

Higher thermal conductivity

≈ 0.60 W m⁻¹ K⁻¹

37°C

Heat transfer rate

Rapid heat transfer

STEP 4

Specific heat capacity

Add the same amount of thermal energy to equal masses of air and water.

☁️

Air

≈ 1.0 kJ kg⁻¹ K⁻¹

AIR

40 30 20 10

20°C

ΔT = 0°C

Lower specific heat capacity

💧

Water

≈ 4.18 kJ kg⁻¹ K⁻¹

WATER

40 30 20 10

20°C

ΔT = 0°C

Higher specific heat capacity

🔥 Same thermal energy added 🔥

MODULE COMPLETE

You explored how buoyancy, viscosity, thermal conductivity and specific heat capacity influence organisms living in water.

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