Exam 21: Heat and the First Law of Thermodynamics

Duff states that equal masses of all substances have equal changes in internal energy when they have equal changes in temperature. Javan states that the change in internal energy is equal to a constant times the change in temperature for every ΔT, no matter how large or how small ΔT is, but that the constant is different for different substances. Which one, if either, is correct?

A gas expands as shown in the graph. If the heat taken in during this process is 1.02 × 10⁶ J and 1 atm = 1.01 × 10⁵ N/m², the change in internal energy of the gas (in J) is how much? ​ ​

A 100-g cube of ice is heated from −120°C to +120°C. In which of the following processes is the greatest amount of energy absorbed by this material?

How much water at 20°C is needed to melt 1 kilogram of solid mercury at its melting point of −39°C? (The heat of fusion of mercury is 2.8 cal/gram).

A 300-g glass thermometer initially at 25°C is put into 200 cm³ of hot water at 95°C. Find the final temperature (in °C) of the thermometer, assuming no heat flows to the surroundings. (The specific heat of glass is 0.2 cal/g⋅°C.)

A styrofoam container used as a picnic cooler contains a block of ice at 0°C. If 225 grams of ice melts in 1 hour, how much heat energy per second is passing through the walls of the container? (The heat of fusion of ice is 3.33 × 10⁵ J/kg).

​The theorem of equipartition of energy states that the energy each degree of freedom contributes to each molecule in the system (an ideal gas) is

An 8000-kg aluminum flagpole 100-m high is heated by the Sun from a temperature of 10°C to 20°C. Find the increase in internal energy (in J) of the aluminum. (The coefficient of linear expansion is 24 × 10⁻⁶ (°C)−1, the density is 2.7 × 10³ kg/m³, and the specific heat of aluminum is 0.215 cal/g⋅°C.)

How much heat (in kcal) must be removed to make ice at −10°C from 2 kg of water at 20°C? (The specific heat of ice is 0.50 cal/g⋅°C.)

Which statement below regarding the first law of thermodynamics is most correct?

If a person in Alaska were locked out of his house on a day when the temperature outside was −40°C, his thick clothing would mostly reduce the loss of thermal energy by

In a thermodynamic process, the internal energy of a system in a container with adiabatic walls decreases by 800 J. Which statement is correct?

Determine the heat capacity (in calories/°C) of a lake containing one million gallons (approximately 4 million kilograms) of water at 15°C.

A 5-gallon container of water (approximately 20 kg) having a temperature of 212°F is added to a 50-gallon tub (approximately 200 kg) of water having a temperature of 50°F. What is the final equilibrium temperature (in °C) of the mixture?

In braking an automobile, the friction between the brake drums and brake shoes converts the car's kinetic energy into heat. If a 1500-kg automobile traveling at 30 m/s brakes to a halt, how much does the temperature rise in each of the four 8.0-kg brake drums? (The specific heat of each iron brake drum is 448 J/kg⋅°C).

Which of the following substances has the greatest specific heat?

An 8000-kg aluminum flagpole 100-m long is heated by the Sun from a temperature of 10°C to 20°C. Find the heat transferred (in J) to the aluminum if the specific heat of aluminum is 0.215 cal/g⋅°C.

We are able to define a mechanical equivalent for heat because

A slab of concrete and an insulating board are in thermal contact with each other. The temperatures of their outer surfaces are 68°F and 50°F. Determine the rate of heat transfer (in BTU/ft2⋅h) if the R values are 1.93 and 8.7 ft2⋅°F⋅h/BTU, respectively.

A 5-g coin is dropped from a 300-m building. If it reaches a terminal velocity of 45 m/s, and the rest of the energy is converted to heating the coin, what is the change in temperature (in °C) of the coin? (The specific heat of copper is 387 J/kg⋅°C.)