Thermal/Wave Review

Which object has more heat energy? A. 30 grams of boiling water B. A 5 kg ice sculpture at 0°C

Which are true? During a phase change… A. The temperature will change B. The entropy of the material will change C. The internal energy of the material changes D. The kinetic energy of the material changes E. Heat is either lost or gained

DO SOME MATH A material has a specific heat of 20 J/gK and a mass of 45 g. It started at 50 °C, and was given 3500 J of heat energy. Assuming no change in phase, what is it’s final temperature?

Relationships Which of the following have a direct relationship with Heat gained/lost? A.Change in Temperature B.Mass C.Phase D.Average Kinetic Energy E.Specific Heat

BONUS CHANCE Absolute Zero Explain to the class the following: 1.What is Absolute Zero 2.What is the temperature in K, and C 3.Which law of thermodynamics defines it

Heat transfer Identify the type of heat transfer that takes place in each of the following: A.A car’s heater blows hot air from the engine B.A magnifying glass burns up an ant C.You burn your mouth while drinking soup D.Wax in a lava lamp expands and rises up E.Food is cooked in an oven (more than one?)

ENTROPY The second law of thermodynamics says that overall entropy of the universe must always increase. Why then can some things decrease in entropy? Write an example of a common entropy decrease and why it does/doesn’t violate the 2 nd law.

More relationships Two containers made of the same material gain the same amount of heat energy. One container is 3 times as massive as the other. The smaller container increases temperature by 15 °C. By how much does the other container’s temperature change? Do you have enough information?

MAKE SOME WAVES Draw the following waves: A. A bright red light B. A dim violet light C. A high-pitched sound

BONUS CHANCE Imitate the sound from an ambulance approaching and then passing you. Remember the Doppler effect!

Doppler Effect (continued) The Doppler Effect also affects light! If an object is fleeing from you rapidly while emitting light, what will happen to the color of the light?

Quick Calcs 2 minutes for the first calc, then half the time for each one after! Find “c”: Q= 20 J, m=5 g, Ti = 30, Tf=40 Find period if 30 waves pass by in 5 seconds. Find wavelength: v = 30 m/s, f = 15 Hz Find frequency if period = 40 seconds. Find wave velocity: λ = 12, f = 10 Hz

Draw the following: A.A wave being absorbed B.An example of diffraction C.A light wave reflected D.A light wave refracted

BONUS CHANCE Resonance Without using any words – come up to the front and act out an example of resonance.

More relationships Which of the following are inversely related: A.Frequency and wave speed B.Wavelength and Frequency C.Wavelength and Period D.Period and wave speed E.Temperature and frequency (for sound) F.Frequency and Period

Answers: 1.B 2.B,C,E C 4.A, B, D, E 5.The lowest theoretical temperature 0 K, -273 C 3 rd law of thermodynamics 6. Convection, Radiation, Conduction, Convection, All 3 7. Water Freezing, Even if water freezes the entropy elsewhere increases as a result

Answers: 8. 5 C, yes 9.Large Amplitude, long wavelength Small amplitude, short wavelength Areas of compression and rarefaction 10. Start with a high pitch and then drop to a low pitch 11. The light will look more red. (frequency decrease) J/gK,.17 seconds, 2 m,.025 Hz, 120 m/s

Answers 13. See examples in “Wave Comparison Charts” Document 14. An example where an object is forced to vibrate at its natural frequency 15. B, D, F