Homework 20: Heat and Temperature I Due: Thursday, January 27, 2011

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1 Name: Date: Period: Homework 20: Heat and Temperature I Due: Thursday, January 27, Fill in the following chart, using the appropriate temperature conversion formulas: Temperature in Kelvin Fahrenheit Celsius Absolute zero Helium boils Temperature on Pluto s surface Cold day in Alaska Refreshing day in Tahiti Hot day in Houston Oven temperature for delicious brownies Surface temperature on Venus Bunsen burner Temperature of the surface of the Sun O K 315 K 750 K 370 o F 72 o F 450 o F 3398 o F 269 o C 30 o C 5800 o C 2. Haley s bowl is filled with kg of 60 o C soup (mostly water) that she stirs with a 20 o C silver spoon of mass kg. The spoon slips out of her hand and slides into the soup. What equilibrium temperature will be reached if the spoon is allowed to remain in the soup and no heat is lost to the outside air? (The specific heat capacity of silver is cal / g o C). Assume that the temperature of the bowl does not change. 3. Calculate the number of calories given off by 350 grams of water cooling from 50 o C to 20 o C. 4. A 30-gram piece of iron is heated to 100 o C and then dropped into cool water where the iron s temperature drops to 30 o C. How many calories does it lose to the water? (The specific heat capacity of iron is 0.11 cal / g o C.)

2 5. What mass of water will give up 240 calories when its temperature drops from 80 o C to 68 o C? 6. When a 50-gram piece of aluminum at 100 o C is placed in water, it loses 735 calories of heat while cooling to 30 o C. Calculate the specific heat capacity of aluminum. 7. What is the final temperature of a 0.88 kg block of ice that absorbs 780 calories of heat, assuming that its initial temperature was 10 o C? 8. A 58-gram sample of ethyl alcohol is removed from a refrigerator where it has been kept at 4 o C and dissolved in 200 grams of room temperature (23 o C) water. What is the final temperature of this mixture? (The specific heat capacity of ethyl alcohol is 0.58 cal/g o C) 9. How much heat is absorbed by 50 grams of ice in order for it to be converted completely to water at 0 o C?

3 10. How much heat is lost by 580 grams of steam at 126 o C when it drops in temperature to 30 o C? 11. How much heat is absorbed by 60 grams of ice at 0 o C in order for it to end up at a temperature of 146 o C? 12. What is the final temperature of 68 grams of ice at 16 o C if it loses 600 calories? 13. How much heat is released by 20 grams of water at 100 o C when it drops down to 45 o C? 14. How much heat is lost when 95 grams of steam condenses to water at 100 o C? 15. How much heat is absorbed by 408 grams of ice at 24 o C when it completely melts, ending at a temperature of 0 o C?

4 16. How much heat is absorbed by 80 grams of water at 100 o C to become steam at 200 o C? 17. How much heat is absorbed by 490 grams of aluminum that rises in temperature from 12 o C to 165 o C? (The specific heat capacity of aluminum is 0.21 cal/g o C) 18. How much heat is released by 260 grams of steam at 142 o C when it drops down to 10 o C? 19. What is the specific heat capacity of 88 grams of an unknown metal that rises in temperature by 130 o C when it absorbs 59 kilocalories? BONUS 20. What will be the final temperature of an ice water mixture if 25 grams of ice at 8 o C is added to 125 grams of water at 25 o C? [Hint: everything ends up in the liquid phase at the end. Be sure to do a chart for the ice!]

5 Heat Transfer 1. Put an X in the appropriate column for each material, based on whether it is a good conductor or a good insulator. Material Good Conductor Poor Conductor Silver Air Glass Iron Wood Paper Copper Good conductors make insulators. Poor conductors make insulators. 2. Convection is the transfer of heat by the mixing of fluids (fluids are or ) that occurs because flow through them. 3. air rises. As it rises, air also tends to expand. As it expands, it. 4. ABSORB or REFLECT? Black objects tend to radiation. White objects tend to radiation. 5. What s going on in a greenhouse? Let s examine this by breaking down the process into four parts. Fill in the following blanks with conduction, convection, or radiation. Visible light passes through glass and is absorbed inside the greenhouse by the air, the floor, the plants, and the glass itself. As the soil heats up, the layers of soil underneath start to get warmer and warmer. Air absorbs sunlight and begins to circulate in the interior. The heated interior gives off infrared waves which cannot pass through the glass, keeping heat trapped inside.

6 6. What s going on when water boils? Let s examine this by breaking down the process into three parts. Fill in the following blanks with conduction, convection, or radiation. The heating element passes heat to the bottom of the pan. Water at the bottom of the pan begins to rise and mix with the cooler water at the top of the pan. The heating element glows orange because it is hot.