If the air temperature isthe same as the temperature of your skin (about 30°C), your body cannotget rid of heat by transferring it to the air. In that case, it gets ridof the heat by evaporating water (sweat). During bicycling, a typical70 kg person’s body produces energy at a rate of about 500 W due tometabolism, 80% of which is converted to heat. (a) How many kilogramsof water must the person’s body evaporate in an hour to get ridof this heat? The heat of vaporization of water at body temperature is2.42 * 10^6 J/kg. (b) The evaporated water must, of course, be replenished,or the person will dehydrate. How many 750 mL bottles of watermust the bicyclist drink per hour to replenish the lost water? (Recall thatthe mass of a liter of water is 1.0 kg.)
Energy transfer
The flow of energy from one region to another region is referred to as energy transfer. Since energy is quantitative; it must be transferred to a body or a material to work or to heat the system.
Molar Specific Heat
Heat capacity is the amount of heat energy absorbed or released by a chemical substance per the change in temperature of that substance. The change in heat is also called enthalpy. The SI unit of heat capacity is Joules per Kelvin, which is (J K-1)
Thermal Properties of Matter
Thermal energy is described as one of the form of heat energy which flows from one body of higher temperature to the other with the lower temperature when these two bodies are placed in contact to each other. Heat is described as the form of energy which is transferred between the two systems or in between the systems and their surrounding by the virtue of difference in temperature. Calorimetry is that branch of science which helps in measuring the changes which are taking place in the heat energy of a given body.
If the air temperature is
the same as the temperature of your skin (about 30°C), your body cannot
get rid of
of the heat by evaporating water (sweat). During bicycling, a typical
70 kg person’s body produces energy at a rate of about 500 W due to
metabolism, 80% of which is converted to heat. (a) How many kilograms
of water must the person’s body evaporate in an hour to get rid
of this heat? The heat of vaporization of water at body temperature is
2.42 * 10^6 J/kg. (b) The evaporated water must, of course, be replenished,
or the person will dehydrate. How many 750 mL bottles of water
must the bicyclist drink per hour to replenish the lost water? (Recall that
the mass of a liter of water is 1.0 kg.)
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