Heat

1. Heat Chapter 10-1 Temperature and Thermal Equilibrium

2. Defining Temperature • Energy must be either added to or removed from a substance to change its temperature. • Example : A substance’s temperature increases as a direct result of added energy being distributed amount the particles of the substance.

3. Thermal Equilibrium • Thermal Equilibrium occurs when two objects in physical contact have the same temperatures. • Thermal Equilibrium is the basis for measuring temperature with a thermometer.

4. Measuring Temperature • Temperature units depend on the scale used. • Scales we use are Fahrenheit (F), Celsius (C ), and Kelvin and (K) . • Formula to Convert from Celsius to Fahrenheit : • Tf = (9/5) Tc + 32.0 • Fahrenheit temperature = (9/5 x Celsius Temperature) +32.0 • Formula for Celsius to Kelvin : • T = Tc + 273.15 • Kelvin Temperature = Celsius Temperature + 273.15

5. Uses of Temperatures Scales

6. Guided Practice • Go to pg. 363 in Book • Sample Problem 10A

7. Heat Chapter 10-2 Defining Heat

8. Heat and Energy • Heat is the energy transfer between substances. • Symbol : Q • Energy is transferred as heat from objects with higher temperatures (hot) to those with lower temperatures (cold). • This transfer of energy changes an object’s temperature.

9. Example: Transfer of Energy as Heat

10. Heat and Energy • Heat has the same units as energy ; Joules ( J ) • Total energy is conserved when changes in internal energy and changes in mechanical energy are taken into account. • Formula :

11. Guided Practice • Open Books to Pg. 369 • Sample 10 B

12. Chapter 10 Section 3 Changes in Temperature and Phase

13. Specific Heat Capacity • Specific heat is the energy required to change the temperature of 1 kg of a substance by 1 C at constant pressure. • Specific heat is related to energy transferred, mass and temperature change by this equation:

14. Determining Specific Heat Capacity • Calorimetry is used to determine specific heat.

15. Specific Heat Quantities

16. Guided Practice • Open Books to Pg. 373 Sample 10C

17. Latent Heat • When energy is used to melt a substance, that energy goes into rearranging the molecules (heat of fusion). • When energy is used to vaporize a substance, that energy mostly goes into separating the molecules (heat of vaporization). • Both heat of fusion and heat of vaporization are classified as Latent Heat. • It takes more energy to vaporize than to melt a substance.

18. Example : Latent Heat

19. Formula :

20. Guided Practice: • Go to page 380 in book • Sample 10 D

21. Chapter 10 Section 4 Controlling Heat

22. Thermal Conduction • Thermal conduction is the transfer of energy as heat through a material by particle collisions. • Substances that rapidly transfer energy as heat are called thermal conductors. • Examples : Metals – copper, silver, iron, steel • Substances that slowly transfer energy as heat are called thermal insulators. • Examples : asbestos, cork, ceramic, cardboard, fiberglass, wood , styrofoam, air , paper

23. Methods of Energy Transfer • Conduction – transfer of heat between substances that are in direct contact with each other. • The better the conductor, the faster the heat transfers.

24. Methods of Energy Transfer • Convection – up and down movement of gases and liquids caused by heat transfer. • As the gas or liquid warms and rises, or cools and falls, it creates a convection current.

25. Methods of Energy Transfer • Radiation – when electromagnetic (light) waves come in contact with and transfer heat to an object. Examples: -Sun warming the earth -a camp fire -microwave oven - a light bulb

26. Methods of Energy Transfer