Which of the following statements about air and water is correct? *
A Both air and water are poor conductors of heat.
B Both air and water are good conductors of heat.
C Air is a poor conductor of heat, but water is a good conductor of heat.
D Air is a good conductor of heat, but water is a poor conductor of heat.
The correct answer and explanation is :
The correct answer is C: Air is a poor conductor of heat, but water is a good conductor of heat.
Explanation:
Thermal conductivity refers to the ability of a material to conduct heat. Materials with high thermal conductivity transfer heat efficiently, while those with low conductivity are poor at transferring heat.
Air is a poor conductor of heat. This is because the molecules in air are relatively far apart compared to those in liquids and solids. As a result, when heat is applied to air, the transfer of thermal energy happens less efficiently. Air is considered a good insulator because of its low thermal conductivity. This is why air can be used in insulating materials, such as the space between the walls of a thermos or double-glazed windows. The low thermal conductivity of air also plays a role in making it less effective at transferring heat between the Earth’s surface and the atmosphere, which is why air feels cooler at higher altitudes.
On the other hand, water is a good conductor of heat. Water molecules are closer together than air molecules, which allows thermal energy to be transferred more efficiently through the liquid. Water’s high heat capacity—its ability to absorb and store heat—also contributes to its effectiveness as a conductor. This is why water is commonly used in systems designed to transfer heat, such as radiators, cooling systems in power plants, or even in cooking (e.g., boiling water to cook food). Water’s ability to conduct heat is significantly better than air, making it a better medium for transferring energy.
This difference in thermal conductivity between air and water explains why water feels cooler than air when you step into it on a hot day (because water absorbs more heat from your skin) and why it is more effective at regulating temperature in various processes.