Exam 14: Heat

A brass rod with a length of 10.0 cm is placed end to end with an aluminum rod with a length of 30.0 cm, and this system is placed between a hot temperature of 100 °C and a cold temperature of 10.0 °C. The thermal conductivities of the brass and the aluminum are 100 W/m °C and 230 W/m °C, respectively. The rods have the same cross-sectional area of 20.0 cm². What is the heat flow from the hot temperature to the cold temperature?

The intensity of solar radiation reaching the Earth is 1,340 W/m². If the sun has a radius of 7.000 × 10⁸ m, is a perfect radiator and is located 1.500 × 10¹¹ m from the Earth, then what is the temperature of the sun?

What is the change in internal energy of 2.00 moles of a monatomic ideal gas as it is heated from 0 K to 100 K?

What is the heat needed to heat 16.0 grams of helium gas at constant volume from 20.0 °C to 85.0 °C?

A 100 g glass container is at 10.0 °C. 200 g of water at 90.0 °C is added to the glass container. What is the final temperature of the water and the glass, in °C? (specific heat of water = 1.00 cal/g °C, specific heat of glass = 0.200 cal/g °C)

The specific heat of ice is 2.10 kJ/kg °C, the heat of fusion for ice at 0 °C is 333.7 kJ/kg, the specific heat of water 4.186 kJ/kg °C, and the heat of vaporization of water at 100 °C is 2,256 kJ/kg. What is the final equilibrium temperature when 5.00 grams of ice at −15.0 °C is mixed with 40.0 grams of water at 75.0 °C?

A primitive space heater consists of an iron ball (radius 10.0 cm) through which electrical current is passed in order to heat the ball (and subsequently the surrounding air). If the temperature of the iron ball is kept at 530 K and the room temperature is 20 °C, what net power is radiated into the room? Assume the ball is a perfect blackbody.

A brass plate with a thickness of 1.00 cm is placed over a copper plate with a thickness of 2.00 cm. Take the thermal conductivity of brass to be 100 W/m °C and that of copper to be 400 W/m °C. What is the effective thermal conductivity for the brass-copper layer?

Radiant energy from the Sun reaches the Earth at a rate of 1.70 × 10¹⁷ W. When 30.0% of the radiant energy is reflected and 70.0% absorbed, the average temperature of the Earth's atmosphere is 253 K or −20 °C. If the atmosphere reflected 40.0% and absorbed 60.0% of the solar radiant energy, then what is the average temperature of the Earth's atmosphere?

Water falls a distance of 50.0 meters. The specific heat of water is 1.00 cal/g °C. What is the increase in temperature of the water after the fall, in °C? Assume that no energy is transferred to the environment in the process.

The specific heat of ice is 2.10 kJ/kg °C, the heat of fusion for ice at 0°C is 333.7 kJ/kg, the specific heat of water 4.186 kJ/kg °C, and the heat of vaporization of water at 100 °C is 2,256 kJ/kg. What is the final equilibrium temperature when 20.0 grams of ice at −15.0 °C is mixed with 5.00 grams of steam at 100 °C?

A 2,000 kg car is traveling at 40.0 m/s and then puts on the brakes and comes to a complete stop. The heat generated at the brakes due to stopping heats up the brakes. The mass of the brake system is 20.0 kg and it has a specific heat of 0.200 kcal/kg °C. What is the increase in the temperature of the brakes?

A 100 gram aluminum container is at 15.0 °C. 150 grams of water at 80.0 °C is added to the aluminum container. What is the final temperature of the water and the aluminum? (specific heat of water = 1.00 cal/g °C, specific heat of aluminum = 0.215 cal/g °C)

The heat of fusion for silver at 960.8 °C is 88.3 kJ/kg and the specific heat of silver is 0.235 kJ/kg °C. What is the energy needed to melt 100 grams of silver starting at 0 °C?

200 joules of heat flows into a 35 g sample. If the temperature increases by 10 °C, then what is the heat capacity of the sample, in J/ °C?

A Styrofoam cooler has a surface area of 2,700 cm² and a wall thickness of 3.0 cm. Styrofoam has a thermal conductivity of 0.010 W/m °C. A 2.0 kg block of ice is placed inside the cooler that has a temperature inside of 2.0 °C. If the heat of fusion for ice is 333.7 kJ/kg and the temperature outside is 35.0 °C, then how long will the ice last? Ignore the effect of the air inside the cooler.

To use 100 Calories of energy, how high would an 80.0 kg person have to climb?

A concrete wall is 15.0 cm thick and has an area of 10.0 m². A layer of wood that is 2.50 cm thick is placed over the wall to reduce the loss of heat by thermal conduction. The thermal conductivity of concrete is 1.70 W/m °C and the thermal conductivity of wood is 0.0400 W/m °C. What is the effective thermal conductivity of the wood-on-concrete system?

A circular window in the wall of a home has a diameter of 25 cm and is made of a single pane of glass 0.30 cm thick. The thermal conductivity for the glass is 0.63 W/(m·K). If 1.6 kJ of heat is lost through the window in 12 s, and if inside the house the temperature is 20 °C, what is the outside temperature?

A 100 g glass container contains 250 g of water at 15.0 °C. A 100 g piece of unknown material at 100 °C is added to the water in the container. The final temperature of the mixture is 19.0 °C. What is the specific heat of the unknown material in J/kg °C? (specific heat of water = 4,186 J/kg °C, specific heat of glass = 837.2 J/kg °C)