1. Dr. Jie Zou PHY 1151G Department of Physics1 Chapter 16 Temperature and Heat (Cont.)

2. Dr. Jie Zou PHY 1151G Department of Physics2 Outline Heat Capacity Specific Heat Calorimetry Conduction, Convection, and Radiation

3. Dr. Jie Zou PHY 1151G Department of Physics3 Heat Capacity Heat capacity, C: Suppose we add the heat Q to a given object, and its temperature increases by the amount ∆T. The heat capacity, C, of this object is defined as C = Q/∆T. SI unit: J/K = J/Cº. The heat, Q, required for a given ∆T is Q = C ∆T. Sign conventions for Q: Q is positive if heat is added to a system. Q is negative if heat is removed from a system. The heat capacity C varies not only with the type of substance, but also with the amount of the substance.

4. Dr. Jie Zou PHY 1151G Department of Physics4 Specific Heat Specific heat, c: c = Q/(m ∆T). SI unit: J/(kg·K) = J/(kg·Cº) The specific heat, c, depends only on the substance, and not on the amount of the substance. For example: c water = 4186 J/(kg·K), c iron = 448 J/(kg·K), c lead = 128 J/(kg·K).

5. Dr. Jie Zou PHY 1151G Department of Physics5 Calorimetry Find the final temperature of the block and the water. (1) The final temperatures of the block and water are equal, since the system will be in thermal equilibrium. (2) The total energy of the system is conserved. The amount of heat lost by one object is equal to the heat gained by the other object in the system.

6. Dr. Jie Zou PHY 1151G Department of Physics6 Example 16-5 A 0.500-kg block of metal with an initial temperature of 30.0 °C is dropped into a container holding 1.12 kg of water at 20.0 °C. If the final temperature of the block-water system is 20.4 °C, what is the specific heat of the metal?

7. Dr. Jie Zou PHY 1151G Department of Physics7 Conduction, Convection, and Radiation Three different ways of heat transfer: Conduction, Convection, and Radiation Examples Conduction: Hold one end of an iron nail in a flame. The heat enters the metal nail at the end that is kept in the flame and the heat is transmitted along the nail’s whole length through conduction. Convection: Heat transfer due to the actual motion of the fluid itself. Liquids and gases (fluids) transmit heat mainly by convection. Radiation: Energy from the sun passes through space and the Earth’s atmosphere by electromagnetic radiation.

8. Dr. Jie Zou PHY 1151G Department of Physics8 Homework Chapter 16, Page 529, Problems: #27, 33, 36.