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

2. Dr. Jie Zou PHY 1151G Department of Physics2 Outline Temperature and heat Temperature scales Heat and mechanical work The Mechanical Equivalent of Heat

3. Dr. Jie Zou PHY 1151G Department of Physics3 Some concepts Heat: The energy transferred between objects because of a temperature difference. Thermal contact: Objects are said to be in thermal contact if heat can flow between them. Thermal equilibrium: When the objects are brought into thermal contact, the hot object cools off while the cold object warms up. After some time in thermal contact, the transfer of heat ceases. At this point, we say that the objects are in thermal equilibrium.

4. Dr. Jie Zou PHY 1151G Department of Physics4 Temperature scales The Celsius scale: Water freezes at zero degrees Celsius (0 ºC), and boils at 100 ºC. The Fahrenheit scale: Water freezes at 32 ºF and boils at 212 ºF.Conversion: T F =, and T C = The Kelvin scale: The Kelvin temperature scale is based on the existence of absolute zero. The zero of the Kelvin scale (0 K) is set exactly at absolute zero. Conversion: T = T C + 273.15.

5. Dr. Jie Zou PHY 1151G Department of Physics5 Measuring heat Heat can be measured in a unit called calorie (cal). In studies of nutrition a different unit, the Calorie (C) is used. 1 C = 1 kcal. Definition for one kilocalorie (kcal): The amount of heat needed to raise the temperature of 1 kg of water from 14.5 ºC to 15.5 ºC.

6. Dr. Jie Zou PHY 1151G Department of Physics6 Heat and mechanical work The mechanical equivalent of heat: One calorie of heat transfer is the equivalent of 4.186 J of mechanical work. 1 cal = 4.186 J. Heat is simply another form of energy that must be taken into account when applying conservation of energy.

7. Dr. Jie Zou PHY 1151G Department of Physics7 Example A 74.0-kg person drinks a thick, rich, 305-C milkshake. How many stairs must this person climb to work off the shake? Let the height of a stair be 20.0 cm.

8. Dr. Jie Zou PHY 1151G Department of Physics8 Homework See online assignment on www.masteringphysics.com www.masteringphysics.com