Heating Curve Lab
Hypothesis: Predict what the "heating curve"
of water will look like as we add constant heat
to the water over time.
Materials:
250mL beaker
calculator
ring stand & clamp
CBL
slit stopper
100mL grad cylinder
temperature probe
ice
hot plate
Procedure:
1) Obtain and wear goggles. Collect materials listed above.
2) Set up CBL and open program on calculator as previously instructed.
3) Place the beaker (with 35 mL water and ~3 ice cubes) onto the hotplate. Suspend
the probe in the water careful not to touch the sides or the bottom.
4) Start the CBL program and turn the hot plate on the highest setting. Record
temperature every 30 seconds in the following table
Time-min
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
Temp-°C
Time-min
8.0
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
12.5
13.0
13.5
14.0
14.5
15.0
Temp-°C
Time-min
Temp-°C
15.5
16.0
16.5
17.0
17.5
18.0
18.5
19.0
19.5
20.0
20.5
21.0
21.5
22.0
22.5
5) When the readings level off, take 5 readings at one temperature. Then, clean up
your area. Turn off the heat & carefully remove the beaker, setting it on a wire
gauze.
Questions:
1) Recall the different states of matter (Solid, Liquid, Gas). How do the water
molecules differ in the liquid and gas states? Explain or draw.
2) Plot your data below as Temperature vs. Time.
120
100
Temperature (°C)
80
60
40
20
0
-20
0
5
10
15
20
25
Time (min)
a) Label the phase changes on your heating curve above.
b) What happens to the molecules as they begin to boil?
c) Did you stop adding heat at any point during the lab? As heat was added what
happened to the energy of system?
d) If you were always adding heat, then why did the temperature trend change?
3) What happens to the E being absorbed from the heat source? Use the heating
curve and your knowledge of atoms to explain.
∆Hvap Practice
∆H = m ∆Hvap
1. How much heat is needed to vaporize 250 g of water at 100 °C and 101.3 kPa?
2. When a quantity of water vapor at 100°C and 101.3 kPa pressure is condensed to
5
the liquid phase, 1.81 x 10 J of heat is released. What mass of water is
condensed?
3. What quantity of heat in joules is required to vaporize 600 g of water at 100 °C
and 101.3 kPa?
Rubric for Mooving through Phase Changes
____ 50 points total
(15 pts ea.)
(20 pts)
Construct a heating curve
Two graphs (checked for accuracy)
Safe and managed completion of the lab during class
____ 20 points total
(2 pts ea.)
Phase changes and energy transfer
Inquiry questions following lab (completion)
____ 30 points total
(5 pts ea.)
∆Hvap and ∆Hfus calculations
Problems given on extra sheet (completion)
Rubric for Energy Content of Foods Lab
____ 40 points
Practice of safe lab procedures and good time management
Completion of lab and clean up
____ 20 points
(10 pts ea)
Data recorded in lab notebook
At least two samples neatly recorded
____ 20 points
(4 pts/?)
Analysis and comparison of own data
Correct completion of lab questions.
____ 10 points
Comparison among class data
Other data is present and commented on.
____ 10 points
Clear summary
Summary is present and incorporates ideas addressed
in lab.