Experiment
27
Dew Point Temperature
On hot summer days, you may notice water droplets forming on the outside of a glass of ice
water. It is commonly said that the glass is “sweating.” Since the glass cannot actually sweat, the
liquid on the glass must come from the air outside the glass. This liquid forms by the
condensation of water vapor that is near the surface of the glass. The air next to the cold glass
has been cooled to the dew point or dew point temperature. The dew point temperature is the
temperature to which air would have to be cooled to become saturated. Once the air is saturated,
the water vapor condens to form a liquid. The same process occurs when dew forms on the
lawn.
In this experiment you will u an EasyTemp temperature probe to make two investigations. In
the first you will measure the temperature of air next to a can of ice water to e if it is colder
than room temperature. In the cond investigation, you will determine the dew point
temperature of the air in the classroom. You will do this by slowly adding ice to water and
watching for condensation to form on the outside of the container. Throughout this process you
will continuously record the temperature of the water. When condensation first forms on the
container, the temperature of the water is the dew point temperature.
房室交界OBJECTIVES
In this experiment, you will
•Compare room temperature to the temperature of air next to a can of ice water.
•Record the temperature of water while ice is slowly added.
•Obrve the formation of condensation.
量子现象•Determine the dew point temperature.
MATERIALS
TI-84 Plus or TI-84 Plus Silver Edition graphing calculator plastic spoon
ice cubes and ice chips
Vernier EasyTemp ring stand
Vernier EasyData application paper towels
shiny, metal can room temperature water
PRE-LAB QUESTIONS
1.To determine the dew point temperature, you will slowly add small pieces of ice to room
被管虫temperature water. After each piece is added, you will wait for the ice to melt. Throughout this proces
s, you will graph the temperature of the water. Draw a rough sketch of what the temperature vs. time graph will look like while the ice melts.
2. In the experiment you will continue to collect temperature data after the small pieces of ice
have melted. Draw a rough sketch of what the temperature vs. time graph will look like after the ice has melted.
Experiment 27
Figure 1
PROCEDURE
Part I Measure the Temperature of the Air Next to a Can of Ice Water
1. Turn on your TI-84 Plus (or TI-84 Plus Silver Edition) graphing calculator and make sure
that it is on the home screen. Plug the EasyTemp probe into the USB port of the graphing calculator. The EasyData application will automatically start and the Main screen will be displayed.
2. U a utility clamp to suspend the EasyTemp probe on a ring stand as shown in Figure 1. The
end of the EasyTemp probe should be about 1 cm above the tabletop.
3. Set up the data collection.
a.Select File from the Main screen, and then lect New.
b.Select from the Main screen.
c.Select Time Graph….
d.Select .
e.Press on the calculator and type 10 as the time between samples in conds. Select
.
f.Press on the calculator and type 90 as the number of samples. Select . The
length of the data collection will be 900 conds (15 minutes).
g.Confirm that time graph ttings are correct. Select .
4. Read the room temperature displayed at the top of the calculator screen. Record it in your
data table.
5. Place 5 or 6 ice cubes in the metal can, fill it with water, and place it away from the
EasyTemp probe.
6. Select to begin data collection. Wait 30 conds and then place the can about 1 mm
from the tip of the EasyTemp probe. Do not touch the probe to the can.
7. Watch the outside of the can. When condensation forms on the can, lect
.
8. A graph of temperature vs. time will be displayed. U to examine data points along the
curve. As you move the cursor right or left, the time (X) and temperature (Y) values of each
Dew Point Temperature
data point are displayed above the graph. Move the cursor all the way to the right side of the graph and record the temperature value in your data table.
9. Sketch the graph as directed by your teacher.
10. Empty the can and dry the outside.
Figure 2
Part II Determine the Dew Point Temperature
停滞不前
11. Fill the dry can half full with room temperature water.
12. Lower the EasyTemp probe into the water (to about 1 cm from the bottom) as shown in
Figure 2.
13. Select to return to the Main screen. Monitor the temperature of the water. Once the
temperature is stable, go to Step 14.
小学二年级作文14. Select to begin data collection. Wait about 30 conds and then add a spoonful of ice
炸金蝉chips to the water. Stir the water while the ice melts. After the ice has melted wait, continue to stir the water for about 10 conds.
15. Add another spoonful of ice chips and again stir the water until it melts. Again wait about 10
conds after the ice has melted. Obrve the can to e if water has condend on the
outside.
16. Repeat Step 15 until you obrve condensation. Once condensation can be obrved, lect
.
17. A graph of temperature vs. time will be displayed. Move the cursor all the way to the right
side of the graph. The temperature displayed is the dew point temperature. Write it down in your data table.
18. Sketch the graph as directed by your teacher.
Experiment 27
19. When you have completed Part II, lect to return to the Main screen. Select from
神灵明the Main screen. Select to exit the EasyData application.
Dew Point Temperature DATA
Part I
Room Temperature (°C)
Air Temperature Clo to the Can of Ice Water (°C)
Part II
Dew Point Temperature (°C)
PROCESSING THE DATA
1.Compare the room temperature to the temperature of the air next to the can of ice water. How
much colder was this air than room temperature?
2. Compare the room temperature, the temperature of the air next to the can, and the dew point
嘀嗒吉他谱temperature.
EXTENSIONS
1.Repeat Part II of this experiment four more times and determine the average dew point
temperature.
2.Collect results from other lab groups and determine the average dew point temperature.
3. Repeat the experiment outside and compare the dew point temperature of the outside air to
that of the inside air. Explain any differences.
