PASCO SE-9790 User Manual

Instruction Sheet
for the PASCO
Model SE-9790

012-07194A

08/99
$1.00

STUDENT BELL JAR

I

A

B

Introduction

The PASCO SE-9790 Student Bell Jar
demonstrates the effect of air pressure on the
boiling point of a liquid, on the size of a balloon,
on the size of a marshmallow, and on the holding
power of a suction cup. It also demonstrates that
air has mass.

The syringe and one-way check valve system
constitute an inexpensive vacuum pump.

An extra connector is provided to permit the
Student Bell Jar to be connected to a PASCO
Pressure Sensor (Absolute, CI-6532 or
Differential, CI-6533), allowing the monitoring of
the pressure inside the chamber.

C

D

F

E

5

G

10

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55

60

cc

H

Equipment

INCLUDED

Part Label Part Name

A bell jar top with connector

B bell jar bottom with O ring

C plastic cup

D suction cup

E tubing with check valve

F tubing with T and check valve

G 60 cc syringe

H tubing for connection with a

PASCO Pressure Sensor

I balloon

Note: Parts E, F, and G constitute the vacuum pump

© 1999 PASCO scientific

ADDITIONAL SUGGESTED

• ScienceWorkshop Interface (300, 500, 700, or 750)

• computer and data acquisition software
(ScienceWorkshop or DataStudio)

Student Bell Jar 012-07194A

Basic Setup and Operation

E

cc

40

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50

55

60

Figure 1

Assembling the vacuum pump

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30

35

5

• Press the suction cup onto the base of the bell
jar.

• Half-fill the plastic cup with very hot coffee, and
place it on the base of the bell jar (Figure 3).

4. Put the lid on the bell jar, hold it there firmly, and
pump the piston of the syringe 10 to 15 times.

Result:

• the balloon will expand

• the marshmallow will expand

• the suction cup will fall off

F

• the coffee will boil

Suggestion: For the coffee boiling experiment,
measure the coffee temperature before and after it
boils.

E

1. Assemble the vacuum pump as shown in Figure 1.

2. Attach part E to the connector on the top of the bell

jar. Twist to secure the connection (Figure 2).

E

Figure 2

Attaching the vacuum pump to the bell jar

15

20

25

A

cc

cup with hot coffee

O ring

B

Figure 3

Completed setup for the coffee boiling demonstration

To Determine the Weight of Air

1. Find and record the original combined mass of
parts A, B, and E.

2. Evacuate the chamber and disconnect A from
E.

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60

3. Do one of the following:

• Place the balloon on the base of the bell jar.

• Place a large, fresh marshmallow on the base of
the bell jar.

3. Find and record the resulting combined mass of
parts A, B, and E .

4. Subtract the resulting combined mass from the
original combined mass to find the mass of air
in the bell jar.

2