Exam 19: Heat and the First Law of Thermodynamics

Consider two cylinders of gas identical in all respects except that one contains O₂ and the other He. Both hold the same volume of gas at STP and are closed by a movable piston at one end. Both gases are now compressed adiabatically to one-third their original volume. Which gas will show the greater pressure increase?

The type of heat transfer that occurs between a heating lamp and the food that it is keeping warm is

How much heat needs to be removed from 100 g of 85°C water to make -5°C ice?

A quantity of ideal gas requires 800 kJ to raise the temperature of the gas by 10.0 K when the gas is maintained at constant volume. The same quantity of gas requires 900 kJ to raise the temperature of the gas by 10.0 K when the gas is maintained at constant pressure. What is the adiabatic gas constant of this gas?

The type of heat transfer that occurs between a stove and a pot placed on it is

Betelgeuse is a star in the constellation Orion. It radiates heat at the rate of 2.70 × 10³⁰ W and has a surface temperature of 3000 K. Assuming that it is a perfect emitter, what is the radius of Betelgeuse? The Stefan-Boltzmann constant is 5.67 × 10^-8 W/(m²∙K⁴).

A 10.0 m² area wall is constructed of three layers. The first layer is 2.00 cm thick and has a thermal conductivity 0.500 W/m∙K. The second layer is 15.0 cm thick and has a thermal conductivity 0.100 W/m∙K. The third layer is 3.00 cm thick and has a conductivity 1.00 W/m∙K. How much heat flows through this wall per hour if one side of the wall is at 20.0°C and the other side is at 0.00°C?

In an isochoric process, the internal energy of a system decreases by 50 J. What is the work done?

330 g of water at 55°C are poured into an 855 g aluminum container with an initial temperature of 10°C. The specific heat of aluminum is 900 J/(kg∙K). What is the final temperature of the system, assuming no heat is exchanged with the surroundings?

The walls of an ice chest are made of 2.00 cm thick styrofoam with a thermal conductivity 0.0300 W/m∙K. The total surface area of the ice chest is 1.20 m². If 4.00 kg of ice at 0.00°C are placed in the chest and the temperature outside the chest is 20.0°C, how long does it take the ice to melt? Remember that the latent heat of fusion of water is 79.6 cal/g.

A 400-g piece of metal at 100°C is dropped into a cup containing 450 g of water at 15.0°C. The final temperature of the system is 40.0°C. What is the specific heat of the metal, assuming no heat is exchanged with the surroundings or the cup?

During which type of process applied to an ideal gas is there no change in internal energy of the gas?

The radius of the Sun is 6.95 × 10⁸ m. It radiates heat at the rate of 5.42 × 10²⁶ W. Assuming that it is a perfect emitter, what is the temperature of the surface of the Sun? The Stefan-Boltzmann constant is 5.67 × 10^-8 W/(m²∙K⁴).

Is it possible to transfer heat from a hot reservoir to a cold reservoir?

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?

Two metal rods, one silver and the other copper, are both attached to a steam chamber, with a temperature of 100°C, at one end, and an ice water bath, with a temperature of 0°C, at the other. The rods are 5.0 cm long and have a square cross-section, 2.0 cm on a side. How much heat flows through the two rods in 60 s? The thermal conductivity of silver is 417 W/(m∙K), and that of copper is 395 W/(m∙K). No heat is exchanged between the rods and the surroundings, except at the ends.

A thermally isolated system is made up of a hot piece of aluminum and a cold piece of copper; the aluminum and the copper are in thermal contact. The specific heat capacity of aluminum is more than double that of copper. Which object experiences the greater temperature change during the time the system takes to reach thermal equilibrium?

An athlete doing push-ups performs 650 kJ of work and loses 425 kJ of heat. What is the change in the internal energy of the athlete?

State the First Law of Thermodynamics.

Describe the technique know as calorimetry.