The Physical Sciences Initiative
Chemistry Inservice
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Evaporation and
Intermolecular Forces
for
Graphic Calculator & Computer
Nov 2001
1
Evaporation and Intermolecular Forces.
Evaporation is an endothermic process, and the magnitude of the temperature
decrease during evaporation is an indication of the strength of the intermolecular
forces present. A small drop in temperature i.e. slow rate of evaporation is an
indication of strong intermolecular forces. This experiment will compare the
temperature changes for propan-1-ol (mol. wt = 60 ) and propanone (mol. wt. = 58)
and the students can determine which of the compounds has the greater
intermolecular forces.
Apparatus
1.
2.
3.
4.
5.
6.
CBL 2 datalogger with DataMate Program
TI-83 Graphing Calculator
Two temperature sensors
One beaker of propan-1-ol and one of propanone.
Filter paper and small elastic bands.
Masking tape.
Setting up the calculator and datalogger
Place the Calculator in the cradle.
Place the CBL 2 datalogger on the underside of the cradle.
Place the Temperature Sensors in channel 1 and channel
2 of the CBL 2.
Connect the Calculator to the CBL 2 using the small connection lead.
Make sure the lead is pressed fully home.
(The connection ports are at the bottom of the Calculator and Lab Pro).
If the sensor is connected before the Calculator is turned on, it will be automatically
detected.
2
Selecting the Sensor and the type of data collection
The Sensor Menu
Data Collection Mode Menu
Turn on the Calculator.
Press APPS (blue key).
From the menu that appears select the Datamate program by pressing the appropriate
number.
Press CLEAR (Removes any data present from previous experiments)
Channel 1 and 2 should show that the Temperature Sensors are attached.
If the Temperature Sensors are not detected in channels 1 and 2 then they must be
selected from the sensor menu.
Press 1 Setup
Press ENTER at channel 1 and select the Sensor from the list
Use the down arrow to move to channel 2
Press ENTER at channel 2 and select the Sensor from the list
You must now decide on the type of data collection you require
Press 1 Setup
Scroll down using the arrow key to select Mode from the menu
Press ENTER.
Press 2 Time graph
Press 2 Change time settings
Time between samples in seconds appears.
Type in 3 and press ENTER
Enter number of samples” appears.
Type in 45 and press ENTER
Press 1 (OK) once
3
Press 1 (OK) again
CBL 2 is now ready to take temperature readings with both Sensors, one every 3
seconds.
Starting the experiment and collecting the data
Students should work in pairs, one to remove the probes from the beakers and attach them to
the bench and the other to operate the calculator.
Place some propan-1-ol in one beaker and propanone in another.
Place a small cylinder of filter paper around the tip of the Temperature Sensors and
secure each with a small rubber band.
.Place one Temperature Sensor in each solution and support them in order to prevent
the beakers tipping over.
Allow the filter paper to soak up the solutions for 30 seconds
Press 2 to start the Datalogging
Allow the first 3 readings to be taken and plotted.
Simultaneously remove both probes from their solutions
Secure each Sensor to the edge of the bench with tape so that the filter paper is clear
of the surface
Readings taken every 3 seconds are being logged and plotted on a graph of
Temperature against Time for each liquid.
Analysing Data
When data collection has stopped two graphs are drawn. The lighter graph represents
channel 1 and the darker graph represents channel 2..
As you move the cursor right or left, the time (X) and temperature (Y) values of each
data point are displayed below the graph.
4
The Up and Down arrows allow you to alternate between graphs. Note the initial (t1)
and final (t2) temperature values for each graph.
Alternatively
Press ENTER. .
Press 1 to return to the Main Menu.
Choose 4 Analyse on the Main Menu screen
Choose 4 Statistics on the Analyse Options screen
Press 1 to select channel 1
Select the Left Boundary by pressing ENTER
Use the Arrow keys to move to the Right Boundary,
Press ENTER.
The Minimum and Maximum temperature values are displayed.
Record these in the Table below.
Repeat the procedure for channel 2
Rinse and dry the Temperature Sensors
Dispose of the solutions as directed by your instructor.
Data and Calculations
propan-1-ol
propanone
o
1. Final temperature, t2
----------
2. Initial temperature, t1
-----------
3. Change in temperature, ∆t
--------oC
5
C
o
C
----------
o
-----------
C
o
C
-------- oC
Transferring Data from the Calculator to a Computer
Connect the Calculator to the Computer using the grey Graph link cable.
On the Computer
Click on the icon for Graphical Analysis.
Choose File and select Import from TI calculator
Select Port
From the window choose COM 1
Click O.K
On the Calculator
Turn off the Calculator by pressing 2 nd . and Off
Turn the computer back on.
Press 2 nd
Link
Press 4 to select Lists
Select L1.by pressing ENTER.
Press the down arrow and press ENTER. to select L2.
Press the down arrow once more and press ENTER. to select L3.
Move the cursor to the top and press the right Arrow to select Transmit
Press 1 or ENTER. to Transmit data
Your data should now appear on the Graphical Analysis screen. You can Analyse this
data following the analysing instructions of LoggerPro found in the Computer version of
these experiments.
6
Intermolecular Forces
Evaporation is an endothermic process, and the magnitude of the temperature decrease
during evaporation is an indication of the strength of the intermolecular forces present. A small
drop in temperature i.e. slow rate of evaporation is an indication of strong intermolecular
forces. This experiment will compare the temperature changes for propan-1-ol (mol. wt = 60 )
and propanone (mol. wt. = 58) and the students can determine which of the compounds has
the greater intermolecular forces.
Apparatus
1. LabPro data logger.
2. PC with Logger Pro software installed
3. Two temperature sensors
4. One beaker of propan-1-ol and one of propanone.
5. Filter paper and small elastic bands.
6. Masking tape.
Setting up the Data logger and PC
THE DATALOGGER
Connect LabPro to the computer via the USB cable .You may need to slide the
plastic window on the side of the data logger to access the port.
Connect the Temperature Sensors to channel 1 and 2 on the LabPro
Attach the power lead to LabPro and turn it on.
THE COMPUTER
Double click on the Logger Pro icon on the desktop.
If there is no icon displayed the program is found by clicking Start followed by
Programs, followed by Vernier Software and finally Logger Pro.
The program should detect the two Temperature Sensors and the window below
is displayed.
7
If the program does not detect the Sensors you are greeted with a welcome
page.
Follow the instructions to open the prepared experiments.
Click on File, select Open.
Double Click on Chemistry with Computers.
Double Click on Exp. 09 Evaporation.
Click on Stainless Steel Temp.
The screen is divided into three main areas.
Graph Window—here data points are plotted as soon as they are recorded.
Meter Window—this shows the reading recorded by the current sensors.
Table Window—Entries are recorded here in columns.(similar to Spreadsheet)
Click on the Setup Collection icon at the top of the screen
Set the data collection for Real Time Collect
Click on the Sampling tab
Set the Experiment length for 120 seconds at a rate of one sample per second
Click on O.K
You are now ready to collect data.
8
Procedure for the Experiment and collecting the Data
Students should work in pairs, one to remove the sensors from the beakers and attach them to
the bench and the other to operate the computer.
Place some propan-1-ol in one beaker and propanone in another.
Place a small cylinder of filter paper around the tip of the Temperature Sensors
and secure each with a small rubber band.
Place one Temperature Sensor in each solution and support them in order to
prevent the beakers tipping over.
Allow the filter paper soak up the solutions for 30 seconds
Click on Collect at the top of the screen
After a few seconds remove both sensors from their solutions
Secure each sensor to the edge of the bench with tape so that the filter paper is
clear of the surface
Readings taken every second are being logged and plotted on a graph of
Temperature against Time for each liquid.
Analysing the Data
Click on the Graph Window where the Data points have been plotted
Click on the Autoscale icon at the top of the screen
Click on Analyse and choose Make Annotation
Type Propan-1-ol and click O.K
A text box appears. Drag the box to the upper graph.
Click on Analyse again and choose Make Annotation
Type Propanone and click O.K
A second text box appears. Drag the box to the lower graph.
Click on Analyse and choose Statistics.
Temp 1 and Temp 2 are already selected , click on O.K
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Two statistic boxes will be shown, one red and one blue. [They may overlap, just
drag them apart using the mouse]
From this data you can record the Max. and Min. Temperatures
Click on Analyse from the top toolbar and select Examine
As you move along the Graph data values can be read for both graphs.
Rinse and dry both Temperature sensors. Dispose of the solutions as directed by your
instructor.
Data and Calculations
propan-1-ol
----------oC
propanone
----------oC
2. Initial temperature, t1
-----------oC
-----------oC
3. Change in temperature, ∆t
--------oC
--------oC
1. Final temperature, t2
10