Chapter 2: Atoms and Heat !!Laws of Thermodynamics: •Law #0: Objects in contact tend to reach the same temperature •Law #1: Energy is conserved •Law #2: Extracting useful energy from heat required a temperature difference •Law #3: The entropy of the universe is always changing !Atoms: •Atoms are about 10^-8cm in diameter. •There are about 50,000 of them in the diameter of a red blood cell (smallest object visible with visible light) !Temperature & Kinetic Energy: •Heat is the shaking of molecules (kinetic energy) •In a solid, despite shaking, atoms remain in the same place •If two objects have the same temperature, their average kinetic energy is the same •The speeds of the molecules are not the same, a lighter molecule will have a higher velocity than a heavy one •lightest molecules are in hydrogen gas •Temperature can be measured in Fahrenheit or Celsius •Physicists use kelvin •Most objects expand when they get warm •Heat can be transferred by conduction, convection, and radiation •An explosion occurs when an object gets so much energy it quickly turns into a hot gas •Energy converted into heat cannot be converted back efficiently •Entropy is a measure of the disorder in molecules. •Warm objects have high entropy !Book / Quiz practice Questions: !1. If you double the energy content of a kilogram of gas, the temperature of the gas (measured on the absolute K scale) A. is unchanged B. increases by the square-root of 2 C. doubles D. is multiplied by 4 !2. About how fast are molecules in air moving? A. 1000 ft/sec B. the speed of light C. 9.8 m/sec D. 9.8 cm/sec !3. Temperature is the measure of A. average momentum B. average kinetic energy C. average velocityD. average total energy !4. In a bucket of water, the instantaneous speed of the molecules is closest to A. zero, since they don’t move B. whatever speed the wood is moving C. approximately 1.7 meters per second D. approximately 1000 feet per second E. approximately 186,000 miles per second !5. A refrigerator operating in a room A. warms the room B. cools the room C. has no effect on the room D. removes water vapor from the room !6. A refrigerator with its door open is operating in a room. It A. warms the room B. cools the room C. has no effect on the room D. removes water vapor from the room !7. A table has the same temperature as the air above it. That means that the molecules in the air and in the table have A. the same average velocity B. the same average energy C. the same acceleration D. the same average mass !8. Ice melts at A. 0 K B. 0 C C. 0 F D. 100 C !9. A gas heater warms a room mostly through A. convection B. conduction C. radiation D. depletion !10. The velocity of sound A. increases when the temperature increases B. decreases when the temperature increases C. depends on the pressure of the air D. is constant, independent of the temperature !11. If gasoline engine produces a hotter explosion, then the efficiency of the engine should A. be the same B. go up C. go down!12. A cup full of water and made of plastic feels warmer than one made of glass because A. plastic is warmed by water B. plastic conducts heat less than glass C. plastic conducts heat better than glass D. plastic dissolves in water !13. The atom with the fewest number of protons is A. helium B. carbon C. hydrogen D. oxygen !14. How many atoms are there in the width of a human hair? About A. 25 B. 125,000 C. 273,000,000,000 D. 6 x 1023 !15. The speed of sound is approximately A. 1 foot per nanosecond B. 1 foot per second C. 1000 feet per second D. 186,000 miles per hour !16. Put a hot glass in cool water. The glass shatters because A. it heats the surface water to boiling B. the outer surface of the glass contracts rapidly, but the inner part doesn't C. the outer surface of the glass expands rapidly D. the rapid conduction of heat triggers strong vibrations !17. Sea level is rising from global warming. The main cause is A. expanding sea water B. melting glaciers C. expanding rock under the sea D. contracting earth (while the water stays constant) !18. The temperature warms by 2 C. That is approximately the same as A. 1 F B. 2 F C. 4 F D. 1/2 F !19. Heat a room using the least energy by A. burning natural gas (methane) B. using natural gas to run a heat pump C. burning coal D. burning gasoline !20. There is almost no hydrogen gas in the atmosphere becauseA. it escapes the Earth's gravity B. there is very little hydrogen in the oceans or land C. hydrogen molecules move slower than oxygen and nitrogen D. hydrogen has all sunk to the Earth's core !21. At Mach 10, if all the energy of a meteorite went into heating the meteorite, its temperature would be about A. 300 C B. 6000 C C. 30,000 C D. 100,000 C !22. The New Orleans levees failed because A. thermal expansion broke therm B. they were made of continuous concrete that could not stand the pressure C. they had leaks at the thermal expansion joints D. they were weaker at the thermal expansion joints !23. If temperature rises by 5 C = 9 F, then the rise in sea level will be about A. 2 inches B. 2 feet C. 12 feet D. 97 feet !24. For a typical auto, the fraction of the gasoline energy wasted as heat is about (careful, this may be a trick question) A. 1% B. 10% C. 20% D. 80% !25. The temperature of the sun A. is always hotter than in the shade B. is always the same as in the shade C. is sometimes cooler than int he shade D. is not well defined !26. When a material is cooled A. it stays the same size B. is contracts C. it expands D. Some materials contract and some expands. !27. The melting temperature of an object is usually A. equal to its freezing point B. higher than the freezing point C. lower than the freezing point D. equal to the boiling point !28. Absolute zero is the temperature of A. frozen waterB. the Universe C. liquid helium D. nothing !29. When a liquid boils, the increase in volume (liquid to gas) is typically a factor of A. 10 B. 100 C. 1000 D. 1,000,000 !30. If the temperature of a gas in a container goes A. stay the same B. double C. become 3000 times larger D. become infinite !31. Firewalking is similar to A. water on a sauce pan B. the space shuttle reentry C. an automobile airbag D. water skiing !32. For gasoline to explode, it needs A. to be mixed with oxygen B. to be mixed with nitrogen C. to be mixed with carbon dioxide D. No mixing needed; just a spark !33. To be more efficient, the
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