1 What is all of this about?

2

3 Hang Glider They can “catch thermals” and rise up hundreds of feet into the air without a motor then glide back down to Earth.

4 Thermal Physics The study of heat energy

5 Heat Assignments  Write down the Key Concepts for  477/1,3,5; 478/10,11  495-7/1-10(with complete statements and answer underlined), and FCAT prep  Workbook pages for Ch16 ( ) All of the above MUST be done in order to do lab.

6 Objectives for this section 1. Know that temperature is directly proportional to the kinetic energy of a substance. 2. Know the temperature scales (F, C, K), their freezing and boiling points, and how to convert temperatures from one scale to another.

7 Objectives, continued: 3. F = 9/5 C C = 5/9 (F-32) 5. K = C Heat energy travels from hot to cold. 7. The lower a material’s specific heat is, the more its temperature rises when a given amount of energy is absorbed by a given mass. Q = mc  t Q units: joules or calories

8 8. Define conduction, convection, and radiation and know examples of each 9. All objects radiate energy st Law of T-D states that energy is conserved nd Law of T-D - thermal energy can flow from colder objects to hotter objects only if work is done on the system rd Law of T-D - absolute zero cannot be reached.

9 Specific Heat, c The amount of heat energy that will raise the temperature of 1 kg of a substance by 1 K. Substance c (J/kg K) Water (liq)4186Copper385 Steam1870Iron449 Aluminum709Gold129 Specific heat is an indicator of how slowly a substance will heat or cool. Of the above substances, which heats at the slowest rate?

10 Specific Heat formula Energy = mass x specific heat x temp change Q=mc  t How much energy must be absorbed by 420 kg of water in a bathtub to raise its temperature from 300 K to 310 K? Q=mc  t Q=420kg (4186 J/kg K) (10 K) Q = J 1.8 x 10 7 J or 1.8 x 10 4 kJ

11 477/2 Math Practice How much heat (Q) is absorbed by a 750-g iron skillet when its temperature rises from 25 o C to 125 o C? See p.476 table for specific heat for iron. m = 750 g tt = 100 o C c iron = J/g o C Q = ?

12 m = 750 g t = 100 o C c iron = J/g o C Q = ? Q = mc  t Q = (750g) (0.449 J) (100 o C) g o C Q = 34,000J Q = 34 kJ

13 477/4 A jeweler heats a 10.0 g silver ring by adding 23.5 J of heat. How much does the temperature of the silver increase? m = 10.0 g Silver Q = 23.5 J c silver = J/g o C  t = ?

14 m = 10.0 g Silver Q = 23.5 J c silver = J/g o C  t = ? Q = mc  t (divide both sides  t = Q by mc) mc  t = 23.5 J g o C (10.0g)(0.235J)  t = 10.0 o C

15 Assignment 477/1,3,5

16 Temperature The temperature of an object or substance is the result of the kinetic energy of the particles in it. The faster the particles are moving, the greater the KE, the greater the temperature of the substance. KE is directly proportional to temperature.

17 Temperature scales

18 Converting temperature From Fahrenheit to Celsius From Celsius to F From C to KelvinK = C Add these to your circle sheet

19 Practice conversions Convert o C to F and K F = 9/5 C + 32 = [9/5 (-290.0)] + 32 F = [9 / 5 x -290] + 32 = -490 o F Convert o C to K K = C K = o C = -17 K

20 #2 Metal in running car engine 388K To C: C = K = = 115 o C To F: F = 9/5C + 32 F = 9/5(115 o C) + 32 F = F = 239 o F

21 #2 110 o F Air in the Desert Temp = To C: C = 5/9(F -32) C = 5/9(110 o F-32) = 5/9(78) = 43.3 o C To K K = C = 43.3 o C K = K

22 Heat & Thermodynamics

23 Relating heat and temperature Heat is thermal energy present in a substance that can be transferred to another substance Heat travels from hotter substances to colder substances Temperature is the measure of the average kinetic energy of the particles within a substance

24 HOT Cold

25 Transfer #1 Conduction –Energy is transferred between particles within a substance or between 2 objects in contact Solids conduct heat best. Insulators don’t conduct heat well.

26 Transfer #2 Convection - transfer of heat by movement of fluids with different temperatures

27 Convection Current

28 Transfer #3 Radiation - transfer of energy by electromagnetic waves

29 Infrared rays provide thermal energy to humans for physical therapy

30 Laws of Thermodynamics 1 st Law of T-D states that energy is conserved during any change. 2 nd Law of T-D - thermal energy can flow from colder objects to hotter objects only if work is done on the system. 3 rd Law of T-D - absolute zero cannot be reached.

31 Assignment 477/1,3,5 478/10, /1-10,28-30, & FCAT Prep Workbook pages: All of the above MUST be done in order to do lab.