Exam 14: Temperature and Heat

Iced tea is made by adding ice to 3.0 kg of hot tea, initially at 80 $\degree$ C. How many kg of ice, initially at 0 $\degree$ C, are required to bring the mixture to 10 $\degree$ C? (L_f = 3.33 x 10⁵ J/kg, c_w = 4186 J/kg· $\degree$ C)

A 2.0-m² Thermopane window is constructed, using two layers of glass 4.0 mm thick, separated by an air space of 5.0 mm. If the temperature difference is 20 $\degree$ C from the inside of the house to the outside air, what is the rate of heat flow through this window? (Thermal conductivity for glass is 0.84 W / m · $\degree$ C and for air 0.0234 W / m · $\degree$ C.)

A brass cube, 10 cm on a side, is raised in temperature by 150 $\degree$ C. The coefficient of volume expansion of brass is 57 *10 ^{- 6}/ $\degree$ C. By what percentage does volume increase?

In a greenhouse, electromagnetic energy in the form of visible light enters the glass panes and is absorbed and then reradiated. What happens to this reradiated electromagnetic radiation from within the greenhouse?

Two stars, A and B, have the same emissivity, but the radii and surface temperatures are different with R_A = 2 R_B, and T_A = 0.5 T_B. Assuming the temperature of space to be negligible, which star radiates the most energy per unit time?

The inside of a house is at 20 $\degree$ C on an early morning when the temperature outside is 15 $\degree$ C. The next morning the inside temperature is the same, but the outside temperature is now 5 $\degree$ C. How much does the energy per unit time lost by conduction through the walls, windows, doors, etc., change for the house from the first morning to the second one.

The Sun is a slightly variable star. What if the surface temperature of the Sun were to increase from 6000 K to 6100 K, what would be the increase in total power radiated assuming no other changes such as radius or emissivity?

A 100-g block of copper is taken from a kiln and quickly placed into a beaker of negligible heat capacity containing 300 g of water. The water temperature rises from 15 $\degree$ C to 40 $\degree$ C. Given c_Cu = 0.10 cal/g· $\degree$ C, and c_water = 1.00 cal/g· $\degree$ C, what was the temperature of the kiln?

A solar heating system has a 25.0% conversion efficiency; the solar radiation incident on the panels is 1000 W/m². What is the increase in temperature of 40.0-kg of water in a 1.00-h period by a 4.00 m² area collector? (c_w = 4186 J/kg · $\degree$ C)

What is the temperature of a system in thermal equilibrium with another system made up of water and steam at one atmosphere of pressure?

I place a 250-g ice cube (initially at 0 $\degree$ C) in a Styrofoam box with wall thickness 1.0 cm and total surface area 600 cm². If the air surrounding the box is at 20 $\degree$ C and after 2 hours the ice is completely melted, what is the conductivity of the Styrofoam material? (L_f = 80 cal/g)

An 100-g piece of copper, initially at 295 $\degree$ C, is dropped into 250 g of water contained in a 300-g aluminum calorimeter; the water and calorimeter are initially at 10.0 $\degree$ C. What is the final temperature of the system? (Specific heats of copper and aluminum are 0.0920 and 0.215 cal/g· $\degree$ C, respectively. c_w = 1.00 cal/g· $\degree$ C)

A 20-kg piece of aluminum (which has a specific heat of 900 J/kg · $\degree$ C) is warmed so that its temperature increases by 5.0 $\degree$ C. How much heat was transferred into it?

Metal lids on glass jars can often be loosened by running them under hot water. Why is this?

A temperature of 233 K equals which of the following?

Normal body temperature for humans is 37 $\degree$ C. What is this temperature in kelvins?

Which best describes the relationship between two systems in thermal equilibrium?

How many calories are equal to one BTU? (One calorie = 4.186 J, one BTU = 1054 J.)

A steel sphere sits on top of an aluminum ring. The steel sphere ( $\alpha$ = 1.10 *10^-5/ $\degree$ C) has a diameter of 4.0000 cm at 0 $\degree$ C. The aluminum ring ( $\alpha$ = 2.40 * 10 ^{- 5}/ $\degree$ C) has an inside diameter of 3.9900 cm at 0 $\degree$ C. Closest to which temperature given will the sphere just fall through the ring?

A swimming pool heater has to be able to raise the temperature of the 30,000 gallons of water in the pool by 10.0 $\degree$ C. How many kilowatt-hours of energy are required? (One gallon of water has a mass of approximately 3.79 kg and the specific heat of water is 4186 J/kg · $\degree$ C.)