1. Chapter 9: Heat

2. Section 9.1: Temperature and Thermal Equilibrium

3. Defining Temperature
Temperature: a measure of the average kinetic energy of the particles in a substance
Adding or removing energy usually changes temperature

4. Internal Energy: energies associated with atomic motion
Thermal Equilibrium: the state in which two bodies in physical contact with each other have identical temperatures
Increasing the temperature of a gas at constant pressure causes the volume of the gas to increase (thermal expansion)

5. Measuring Temperature
Thermometer a device that measures temperature.
Mercury
Alcohol
Metal coils
Digital

6. Measuring Temperature
Calibrating thermometers requires fixed temperatures.

7. Measuring Temperature
Celsius-Fahrenheit Temperature Conversion
Celsius-Kelvin Temperature Conversion

8. Example Problem
Oxygen condenses into a liquid at approximately at K. To what temperature does this correspond on both the Celsius and Fahrenheit temperature scales?

9. Section 9.2: Defining Heat

10. Heat and Energy
Heat: energy transferred between objects because of a difference in their temperatures.
Energy is transferred as heat from objects with higher temperatures to those with lower temperatures.
The greater the temperature difference is between objects, the greater the rate of energy transfer between them as heat.

11. Units of Heat Heat is measured in units of joules(J)
1 calorie (cal) = J
1 kilocalories(kcal) = 4186 J
1 Calorie = 1kcal = 4186 J
1 British thermal unit = 1055 J
1 therm = X 10⁸ J

12. Thermal Conduction
Thermal conduction is the transfer of energy from differences in temperature. Energy between particles as they collide within a substance or between two objects in contact.
The rate of thermal conduction depends on the substance.
Substances that rapidly transfer energy as heat are called thermal conductors.
Substances that slowly transfer energy as heat are called thermal insulators.

13. Convection and radiation also transfer energy.
Convection involves the movement of cold and hot matter.
Electromagnetic radiation is when objects reduce their internal energy by giving off electromagnetic radiation of particular wavelengths or are heated by electromagnetic radiation.

14. Heat and Work
The sum of the changes in potential, kinetic, and internal energy is equal to zero.
Conservation of Energy
PE + KE + U = 0
If changes in internal energy are taken into account, the total energy is conserved.

15. Sample Problem ΔPE + ΔKE + ΔU = 0
What is the change in internal energy when the change in potential energy is 20 J and the change in kinetic energy is 35 J?
ΔPE + ΔKE + ΔU = 0
20 J + 35 J + ΔU = 0
ΔU = -55 J
Given: ΔPE = 20 J ΔKE = 35 J Unknown: ΔU = ?

16. Section 9.3: Changes in Temperature and Phase

17. Specific Heat Capacity
Specific Heat Capacity: the energy required to change the temperature of 1 kg of a substance by 1°C
Q = energy transferred as heat (J)
m = mass of substance (kg)
C = specific heat capacity
ΔT = temperature change ( K or C)

18. Calorimetry: method used to determine specific heat capacity
The energy absorbed by one substance is equal to the energy lost by another.
Qlost = Qgained

19. Example Problem
What is the final temperature when a 3.0 kg gold bar at 99°C is dropped into 0.22 kg of water at 25°C?
(Cp x m x ΔT)water = (Cp x m x ΔT) gold
(4186J/kg°C)(0.22kg)(Tf - 25°C) = (129J/Kg°C)(3.0k g)(99°C- Tf)
921Tf – 23,023 = 38,313 – 387Tf
1308 Tf = 61,336
Tf =47 ° C

20. Phase Change & Latent Heat
Phase Change: physical change of a substance from one state to another at constant temperature and pressure
When substances melt, freeze, boil, condense, or sublime, the energy added or removed changes the internal energy without changing the temperature.

21. Latent Heat: energy per unit mass that is transferred during a phase change of a substance
Formula of latent heat:
Latent heat is measured in the units
Lf = Heat of fusion, the latent heat of a substance that is melting.
Lv = Heat of vaporization, the latent heat of a substance that is vaporizing.