What property of water allows it to resist temperature change and help regulate body temperature in organisms?

• A. Rapid evaporation of water
• B. Water's high specific heat due to hydrogen bonding
• C. Water's low heat capacity
• D. Strong covalent bonds in water molecules

Answer: (B)

Water moderates temperature because of its high specific heat, which comes from the extensive hydrogen bonding between water molecules. When heat is added, much of that energy goes into disrupting these bonds rather than increasing the molecules’ kinetic energy, so the temperature rises only a little. This helps maintain stable body temperature in organisms, because body fluids can absorb and store heat from metabolism or the environment without a rapid spike in core temperature. The body also uses water’s high heat of vaporization for cooling—evaporating sweat requires a lot of energy, which removes heat from the body.

Rapid evaporation isn’t the reason water resists temperature change, though evaporation can cool. The important factor is the hydrogen-bonded network that makes water’s heat capacity high. Covalent bonds inside a water molecule are strong, but they don’t govern how water's temperature responds to heat in the same way the intermolecular hydrogen bonds do. A low heat capacity would make temperature change easier, which is the opposite of what water provides.