January 6-7, 2011

1. January 6-7, 2011

2. What is the difference… • Between a hot and cold cup of coffee? • Temperature • Temperature is a man-made, arbitrary scale indicating which direction heat is flowing

3. Temperature • Temperature: a measure of the AVERAGE kinetic energy of the particles in a substance • The molecules of hot coffee are moving faster than the molecules of the cold coffee • More Heat=More Thermal Energy=More Kinetic Energy

4. Temperature • Temperature measures the average kinetic energy per molecule • Liquids, solids, and gases expand differently when heated. • Thermometers use an expanding liquid to measure temperature.

5. Physics in Action • Which of the following is TRUE for the water molecules inside popcorn kernels during popping? • Their temperature increases. • True • They are destroyed. • False • Their kinetic energy increases. • True • Their mass changes. • False

7. Gabriel Fahrenheit Simplified • Fahrenheit took a glass tube and graduated it…made marks: 1,2,3…etc. • He used water as the standard. We often use water as our standard for things-its cheap and easy to get! • He froze some water and the mercury in the tube dropped to the mark he made…32 degrees. When water boiled the mercury in the tube rose to 212 degrees.

8. Anders Celsius Simplified • When Celsius investigated the subject of temperature he did something a little differently. • He did not mark off the glass tube. He simply put it into frozen water and where the mercury landed he called that 0 degrees. • When water was boiling and the mercury rose and leveled off he called that 100 degrees. • This is the one used most around the world.

9. What do I need to Know? • Freezing point (Melting Point): 0*C/32*F • Boiling point (Condensation Point): 100*C/212*F

11. Lord Kelvin Simplified • Kelvin was interested in a more philosophical approach to the behavior of matter at different temperatures. • He wondered what would happen if there was a condition of NO HEAT. At “absolute” zero, what would the conditions be? • At zero Kelvin, at absolute zero, all motion would cease since temperature is an indirect measure of the motion of molecules. • So, if there was no heat there would be no motion and thus no temperature. • But a condition of absolute zero cannot exist since there is no absolute NO motion. • Everything moves relative to SOME frame of reference. So everything has SOME temperature! • Atoms vibrate. Electrons revolve around the nucleus of every atom. • Everything moves relative to something.

12. Heat and Temperature • Heat and Temperature are different. • Heat is a type of ENERGY; measured in joules. • All things are made of atoms and the atoms are always moving. • Heat: is the TOTAL l kinetic energy because of ALL the atoms in an object.

13. Think about it… Why does JELLO call for hot water? The hot water has more internal energy The molecules of the hot water have a higher kinetic energy and therefore disperse the coloring more quickly!

14. Check your Understanding… • Which has more internal energy…a hot cup of coffee or an iceberg? The iceberg has more internal energy than the cup of coffee because it is made up of a much larger number of molecules!

15. Internal Energy • Internal Energy: the energy of a substance due to the random motions of its component particles and equal to the TOTAL energy of those particles Why doesn’t a sparkler burn a little kid? A sparkler has a very high temperature but a very small amount of internal energy.

16. When Objects are Heated • Materials expand when they are heated. • This is because the increase in heat energy makes the atoms move around more • The atoms bounce into each other, moving farther apart and the material expands. • Hot objects=atoms move farther apart=expand • When a material is cooled, the atoms move together and the material contracts. • Cold Objects=atoms move together=contract

17. Direction of Thermal Transfer • Imagine a can of warm fruit juice immersed in a large beaker of cold water. • After about 15 minutes, the can of fruit juice will be cooler and the water surrounding it will be slightly warmer. • Eventually, both the can and the fruit juice and the water will be at the same temperature.

18. Thermal Equilibrium • Thermal Equilibrium: the state in which two bodies in physical contact with each other have identical temperatures. • Which of the following are at thermal equilibrium?

19. How do you know? • A hot copper pan is dropped into a tub of water. If the water’s temperature rises, what happens to the temperature of the pan? • The pan’s temperature decreases if the water’s temperature increases. • How will you know when the water and copper pan reach thermal equilibrium? • The water and pan have reached equilibrium when their temperature are the same.

20. Phase Change • 3 States of Matter: Solid, liquids, and gases • Whether the substance is in its solid, liquid, or gaseous state depends on the TEMPERATURE! • Temperature is speed! (whole thing) • Heat is speed AND mass! (each atom)

21. DRAW THIS!!!

22. -Gain energy Loss of energy- >100*C 212*F <0*C/32*F

24. Solid, Liquid, or Gas? • Water at 50*C • Liquid • Water at 120*C • Gas • Water at 10*F • Solid • Water at -5*C • Solid • Water at 100*C • Gas

25. Gain or lose energy? • When water freezes? • Loses-got colder • When water boils? • Gains-got hotter • When ice melts? • Gains-got hotter • During condensation? • Loses-got colder • When water turns to steam? • Gains-got hotter

26. How Heat Travels • Heat always transfers from hot to cold. • Heat does not rise (hot air rises).

28. Check for Understanding • You put ice into a cup of hot chocolate. The ice gives its cold to the liquid. Yes or no and why? • If two cups of hot chocolate, one at 50*C and the other at 60*C, are poured together in a large container, which way did the energy transfer? • What will the final temperature of the double batch be?

29. A cup of hot tea is poured from a teapot and a swimming pool is filled with cold water. Which one has a higher total internal energy? • The water in the swimming pool has more internal energy. The much larger volume, and therefore the much larger number of particles, more than makes up of the lower temperature. • Which has a higher average kinetic energy? • The hot tea has a higher average kinetic energy, because temperature is proportional to average kinetic energy.

30. Lab Explanation