Type:
Double
Date:________
Objective:
The Equilibrium Temperature and
Calorimetry I and II
Homework: Do CONCEPT Q. # (16),
Do PROBLEMS # (47, 78, 84) Ch. 12
AP Physics “B”
Mr. Mirro
Date: ________
Equilibrium Temperature I
Ex 1: As part of March, National Nutrition Month, John took part in a health fair at school. Going from
one exhibit to another a computer suddenly caught his eye. The computer was flashing the food
Calories of some popular fast food choices. John noticed that his favorite fast food was beginning to
scroll across the screen. John at first watched with curiosity, which then quickly turned into disbelief
as he read the screen: Double Whopper with Cheese – 1020 Cal, 57 % fat, 1460 mg Sodium.
If 5 % of this energy could be converted into work, how high could a 1 N (1/4 lb) object be raised ?
Let the Mechanical Equivalent of Heat Energy ⇒ 1 Cal = 1 k cal = 4186 J [CutnellP12.47sim]
Ex 2: A precious stone dealer wishes to find the specific heat capacity of a 0.030 kg gemstone. The
specimen is heated to 95 °C and then placed in a 0.15 kg copper (c = 387 J/kg °C) vessel that
contains 0.080 kg of water (c = 4186 J/kg °C) at an initial equilibrium temperature of 25 °C.
When equilibrium is reestablished, the temperature of the water-stone system is 28.5 °C. In the loss
of heat to the external environment is negligible, what is the specific heat capacity of the specimen ?
[CutnellP12.39]
Ex 3: How could we determine the amount of heat necessary to change 1 kg of super cooled ice at -10 °C
into super heated steam at 120 °C ? [General]
a. Explain the method. _____________________________________________________________
b. Amount of heat required to change the temperature of 1 kg of ice at -10 °C to ice at 0 °C.
[Note: cice = 2050 J/kg °C]
c. Amount of heat required to melt 1 kg of ice at 0 °C.
[Note: LF = 33.5 x 104 J/kg]
d. Amount of heat required to raise the temperature of 1 kg of cold water at 0 °C to 100 °C.
e. Amount of heat required to turn 1 kg of water at 100 °C to steam at 100 °C.
[Note: LV = 22.6 x 105 J/kg]
f. Amount of heat required to convert 1 kg of steam at 100 °C to super heated steam at 120 °C.
[Note: csteam = 2010 J/kg °C]
g. On a separate piece of graph paper, develop the phase diagram of temperature (T in °C)
versus thermal energy (Q in Joules). Scale the horizontal axis for 1 x 105 Joules per box.
AP Physics “B”
Mr. Mirro
Date: ________
Equilibrium Temperature II
Ex 1: If the price of electrical energy is $ 0.10 per kilowatt-hour, what is the cost of using electrical energy
to heat the water (ρH2O = 1000 kg/m3) in a swimming pool (12.0 m x 9.0 m x 1.5 m) from 15 °C
to 27 °C ? Let 1 kWh = 3.6 x 106 J. [CutnellP12.45]
Ex 2: At the beach a 2.4 kg bag of ice in a cooler completely melts in 8.0 hrs. The temperature of the ice
and the resulting liquid water is 0 °C. What is the average power entering the cooler ?
[CutnellP12.58]
Ex 3: A woman finds the front windshield of her car covered with ice. The ice has an initial temperature of
T0 = - 12 °C and is 4.5 x 10-4 m thick covering an area of 1.25 m2. If she turns on the car’s
defroster,
how much heat in joules does the device need to supply to completely melt the ice ? The density of ice
is ρ = 917 kg/m3. [CutnellP12.57]
Ex 4: Two students, are performing a physics laboratory exercise to measure the specific heat of silver. One
knows that silver has a density of 10.5 x 103 kg/m3 and the other knows that silver melts at 962 °C.
The laboratory equipment includes a cube of silver 2.0 cm on each side and a 75 g beaker made of
glass (cglass = 0.84 kJ/kg °C) filled with 100 g of water (cH2O = 4.186 kJ/kg °C). Both the beaker
and the water are initially at 20 °C. [PrinctonReviewFR9.1]
a. What is the mass of the silver cube ?
The silver cube is heated in an oven to a temperature of 500 °C. The cube is quickly lifted out of the
oven and placed into the water. A thermometer is placed in the water. The student then records the
maximum temperature reading on the thermometer to be TEQUILIB = 41 °C.
b. Write down equations for the heat gained by the water, the heat gained by the glass and the
heat lost by the silver cube.
Water: QH2O ⇒
Glass: Qglass ⇒
Silver: QAg ⇒
c. Using the conservation of thermal energy, set up the equation expressing the calorimetry of
the experiment as the silver cube-water system cool to their equilibrium temperature.
[Assume that heat losses to the air and thermometer are negligible.]
d. Determine the specific heat of silver.
e. If the silver cube was at 20 °C just before it was placed in the oven and it reached its final
temperature of 500 °C in 5 minutes, find the rate (in watts) at which thermal energy was
absorbed by the cube during the heating.