Which factor explains why water causes faster heat loss compared with air?

• A. Higher humidity
• B. Higher density
• C. Greater thermal conductivity of water
• D. Longer exposure time

Answer: (C)

Heat transfer rate is governed by how well the medium can conduct heat. Water has a much higher thermal conductivity than air, so for the same surface area and temperature difference, heat moves from the object into the water much more quickly. That higher conductivity directly translates to a larger heat flux, meaning faster heat loss. Humidity isn’t the controlling factor here, and while density and convection matter in other ways, the key reason water speeds up heat loss is its greater thermal conductivity. Longer exposure time describes duration, not the medium’s ability to transfer heat.