Temperature and Heat

1. Temperature and Heat Heat Temperature Specific Heat Phases of Matter Latent heat Heat Transfer Kinetic Theory

2. Heat Some two hundred years ago heat was thought to be an invisible fluid called caloric, which flowed like water from hot objects to cold objects. Caloric appeared to be conserved – that is, it seemed to flow from one place to another without being created or destroyed. This idea was the forerunner of the law of conservation of energy.” Hewitt (1998). Conceptual Physics (8th Ed.) p. 306.

3. Heat is Kinetic Energy • During the French Revolution Count Von Rumford (Benjamin Thompson) was boring cannons for the Bavarian army and he notice: “I perceived, by putting my hand into the water and touching the outside of the cylinder that, Heat was generated; … at 2 hours and 30 minutes it (the water) ACTUALLY BOILED…without any fire.” (Hakim, 2005. The Story of Science: Newton at the Center, p. 318.) • The generation of heat was related to the kinetic energy of truing the cannon barrel.

4. Heat • Heat is energy and thus has units of Joules. • However, heat has a special unit of calorie. • A calorie is the heat needed to raise one gram of water by 1Co. • 1cal = 4.186J • 1kcal = 1000 cals • 1Cal (food calorie) = 1000 cals

5. Temperature • Temperature is a measure of the average kinetic energy of the molecules of a substance. • A thermometer measures this KE as the molecules collide with the thermometer’s bulb.

6. Temperature ScalesFreezing point to boiling point of water • Fahrenheit: 32 to 212, range of 180 degrees. • Celsius: 0 to 100, range of 100 degrees. • Kelvin: 273 to 373, range of 100 degrees.

7. Kelvin Scale • At constant pressure the volume of a gas changes by 1/273 of its volume at 0Co with each 1Co change in temperature. • At 100Co the volume is 100/273 greater than it is at 0Co. • When temperature is reduced to -100Co the volume is reduced by 100/273. • At -273 0Co the gas is reduced to 273/273 and the volume is 0.

8. HeatHeat is the net energy transferred from one object to another because of a temperature difference. Total Energy Includes: • molecular translation form place to place, • molecular vibration, • molecular rotate.

9. Specific Heat • Each substance has its own specific heat. • The specific heat of any substance is the amount of heat it takes to raise 1kg of the substance by 1Co. • Specific heat of water = 1.000 kcal/kgCo. • H = mcDT, Where: m = mass c = specific heat DT = change in temperature.

10. Specific Heat Table

11. Phases of MatterSolid • Molecules arranged in a rigid crystalline structure. • Expansion occurs during heating because molecules vibrate with grater amplitude.

12. Phases of MatterLiquids • Molecules not in a lattice. • Molecules can vibrate and rotate. • Molecules are still close together. • Take the shape of container.

13. Phases of MatterGas • Molecules relatively far apart. • Molecules have high speed of Kinetic Energy.

14. Latent Heat • Heat associated with a phase change. • Lf = latent heat of fusion • H = m Lf = heat needed to melt a substance. • Lv = latent heat of vaporization • H = m Lv = heat needed to vaporize a substance.

15. Latent Heat Latent heat of fusion used to bread apart the crystalline lattice of water.

16. Latent Heat Graph

17. Heat Transfer • Conduction • Convection • Radiation

18. Heat TransferConvection in a House

19. Heat TransferThe Wind Sea Breeze Land Breeze

20. Heat TransferConvection on the Sun

21. Heat TransferThermos Bottle

22. Kinetic Theory & Gas LawsPressure & Number of Molecules • Pressure is directly proportional to the number of gases molecules present. • p a N

23. Kinetic Theory & Gas LawsPressure & Temperature • At constant volume pressure is directly proportional to the Kelvin temperature. • p a T

24. Kinetic Theory & Gas LawsPressure & Temperature A boiler explosion broke this locomotive into small pieces and sprayed them, and the crew, over a wide area of Florida. http://afu.com/steam/

25. Since we Mentioned Steam Engines Thomas and his prototype

26. Kinetic Theory & Gas Laws Pressure & VolumeBoyle’s LawRobert Boyle (1627 – 1691) • At constant temperature pressure is inversely proportional to the volume. • p a 1/V where V = volume. http://www.grc.nasa.gov/WWW/K-12/airplane/aboyle.html

27. Kinetic Theory & Gas Laws Temperature & VolumeCharles’ Law Jacques Charles (1746-1823) • The volume of a fixed amount of gas at constant pressure is directly proportional to its absolute (Kelvin) temperature. • V = kT http://www.grc.nasa.gov/WWW/K-12/airplane/aglussac.html

28. Kinetic Theory & Gas Laws Ideal Gas Law • Putting all three of these together the Ideal Gas Law is obtained. • P a (NT)/V • The proportionally can be used to take ratios for calculations. • p2/p1 = (V1/V2)(T2/T1) assuming a constant number of molecules, N.

29. Kinetic Theory and AtomsJohn Dalton (1766 – 1844) • All matter is composed of tiny particles. • All atoms of each element are identical (he didn’t know about isotopes.) • Atoms are not created or destroy in chemical reactions (conservation of matter.) • Elements bond in whole ratios to form compounds. • Chemical reactions are the union and separation of atoms.

30. Resources Hakim, (2005). The Story of Science: Newton at the Center. Hewitt, (1998). Conceptual Physics (8th Ed.) Hewitt, Suchocki, & Hewitt, (1999). Conceptual Physical Science (2nd Ed.) http://www.bbso.njit.edu/ Shipman, Wilson, and Todd, (2003). An Introduction to Physical Science (10th Ed.)