Overview
This chapter presents a short historical development of ideas about heat, then develops the theoretical basis for the modern understanding of temperature and heat. Concepts of heat and the kinetic molecular theory are closely linked, and observations of heat interactions provide evidence in favor of the kinetic theory. In turn, the particle nature of matter becomes more realistic from the quantitative and qualitative evidence provided by heat. The modern understanding of heat, which is derived from thermodynamics, is that heat is a measure of the amount of internal energy transferred from one object or system to another object or system. Heat corresponds to work at a molecular level and they are not considered separate concepts.
Energy, work, and heat are measured in units of joules in science classes for science majors. Calories and Btus are also discussed in this text for nonscience majors because these are the heat measurements in everyday use. A measured amount of heat will affect the temperature of any substance, but the change in temperature will vary with the substance. Each substance has its own specific heat, which is usually smaller than that of water. Thus, less heat (internal energy) is required to raise the temperatures of these substances and, as they cool, they release less heat, or release less internal energy, than water. Conduction, convection, and radiation are important concepts of heat flow, and understanding them will become more important as present-day lifestyles place more and more demands on the energy supply.
This chapter presents a short historical development of ideas about heat, then develops the theoretical basis for the modern understanding of temperature and heat. Concepts of heat and the kinetic molecular theory are closely linked, and observations of heat interactions provide evidence in favor of the kinetic theory. In turn, the particle nature of matter becomes more realistic from the quantitative and qualitative evidence provided by heat. The modern understanding of heat, which is derived from thermodynamics, is that heat is a measure of the amount of internal energy transferred from one object or system to another object or system. Heat corresponds to work at a molecular level and they are not considered separate concepts.
Energy, work, and heat are measured in units of joules in science classes for science majors. Calories and Btus are also discussed in this text for nonscience majors because these are the heat measurements in everyday use. A measured amount of heat will affect the temperature of any substance, but the change in temperature will vary with the substance. Each substance has its own specific heat, which is usually smaller than that of water. Thus, less heat (internal energy) is required to raise the temperatures of these substances and, as they cool, they release less heat, or release less internal energy, than water. Conduction, convection, and radiation are important concepts of heat flow, and understanding them will become more important as present-day lifestyles place more and more demands on the energy supply.