QUESTION #680

# When carpet and a marble floor are at same room temperature, why does carpet feel warmer than a marble floor?

Your sense of an object's temperature actually depends on the direction of heat flow between it and your skin. When heat flows from the object to your hand, for example, the object feels warm to the touch. When heat flows from your hand to the object, it feels cool. You can confirm this by soaking one hand in warm water and the other in cold. Then, put each hand into room temperature water. The warm hand will make you think the water is cool, the cold hand will make you believe the water is warm. Temperature difference between an object and your skin is one condition resulting in heat flow, but there are others. Wind chill factor makes the same air temperature feel different to your skin because convection removes heat more quickly from you skin when air is moving over it. Another factor affecting the flow of heat is conductivity, or the ability of material to transfer heat efficiently. Some materials, like metals and marble, are good conductors and allow heat to flow easily from and to your skin. Other materials (called insulators), like the material in carpeting, are poor conductors and do not allow heat to flow very easily. So even when they are at the same temperature, a cold marble floor transfers heat quickly away from your feet, while a cold carpet prevents that flow from occuring as quickly. That makes the marble "feel" colder.
Answered by: Paul Walorski, B.A., Part-time physics instructor

Answered by: Tom Young, B.S., Physics teacher at Whitehouse High School

How hotsomethings feels (other than its actual temperature) is dependant on its heat capacity and the rate at which heat is removed from the surface. In this case, therelevantt way of looking at heat capacity is as the energy required to heat up a certain volume of material. Since temperature is just the average kinetic energy of atoms, the heat capacity per unit volume is dependant on the number of atoms per unit volume. Heat conduction is also closely related to the atom number-density of a material, but also depends on the structure and the freedom of the atoms to move within the material and pass on their energy to other atoms. Marble, being a dense solid requires a lot of energy to pass from your body to warm up. It also has a reasonable rate of heat conduction, so the surface remains cold for some time when in contact with your body. Carpet, on the other hand has a very small number density, because most of the volume is occupied by air. It therefore warms up very quickly to the temperature of your skin, at which point it is preventing further heat loss and feels warm. In reality the carpet never reaches the temperature of your skin, because it is constantly being cooled by the replacement of warm air with cool air. So unlike marble, the main cooling process for carpet is not conduction, but convection.