Exam 11: Heat

Consider two neighboring rectangular houses built from the same materials. One of the houses has twice the length, width, and height of the other. Under identical climatic conditions, what would be true about the rate that heat would have to be supplied to maintain the same inside temperature on a cold day? Compared to the small house, the larger house would need heat supplied at

Glass has more than three times larger thermal conductivity than air. Yet glass-wool (glass fibers and air) air spaces. Why is glass-wool better although glass has larger conductivity than air?

Ice cream, when eaten, gives about 2100. Calories/kg to the body. On the other hand, the body must give back energy to warm it up to body temperature (37°C). Assuming ice cream has similar thermal properties to water: (a) 1/2 kg produces how much energy? (b) 1/2 kg absorbs how much energy to reach 37°C? (c) What is the net gain or loss (eating 1/2 kg ice cream)?

You blow on food to cool it. Blowing increases

The specific heat of ice is about ________ the specific heat of liquid water.

Which of the following best explains why sweating is important to humans in maintaining suitable body temperature?

In the vacuum of space, one gets rid of unwanted heat from spacecraft by utilizing

A layer of insulating material with thermal conductivity K is placed on a layer of another material of thermal conductivity 2K. The layers have equal thickness. What is the effective thermal conductivity of the composite sheet?

A large fan placed in a closed room is effective by enhancing

A substance with a greater specific heat ________ has a larger heat capacity.

Consider a light bulb, in empty space, radiating 200. watts with its filament heated to 2800.°C. Assuming it is a good approximation to a black body. (a) What is the area of the filament? (b) If placed in an oven, with walls at 800.°C, what is its net power radiated now?

At higher altitudes it takes ________ time to bring water to a boil on a stove.

150 kcal of heat raises the temperature of 2.0 kg of material by 400 F°. What is the material's specific heat capacity?

It is a well-known fact that water has a higher specific heat capacity than iron. Now, consider equal masses of water and iron that are initially in thermal equilibrium. The same amount of heat, 30. calories, is added to each. Which statement is true?

A block of ice at 0°C is added to a 150. g aluminum calorimeter cup that holds 200. g of water at 10°C. If all but 2. g of ice melt, what was the original mass of the block of ice?

The heat of fusion of lead is 5.9 kcal/kg, the heat of vaporization is 207. cal/kg, and its melting point is 328°C. How much heat is required to melt 50. g of lead initially at 23°C? (The specific heat of lead is 0.031 kcal/kg-C°. )

Which of the following represents the "Mechanical Equivalent of Heat"?

A 2.0 kg aluminum block is originally at 10°C. If 140 kJ of heat is added to the block, what is its final temperature?

A 100. gram steel bullet moves at 250. m/s just before imbedding itself into a thick anchored wood post. If 40.% of the initial kinetic energy goes into heating the bullet (steel c = 460.J/kg-C) (a) how hot does the bullet become if it initially is at 25.°C? (b) what would be the bullet's temperature if it had been twice as massive ( 2 times 100. grams)?

50 g of lead (c = 0.11 kcal/kg. °C) at 100°C is put into 75 g of water at 0°C. What is the final temperature of the mixture?