Try out of

Pressure Law experiment

Pressure Law Experiment I

The Bourdon gauge

is not precise.

Temperature/ degree Celsius

Pressure/ kPa

84.2 1.1

63.0 1.05

42.0 1.0

Absolute temperature = -375oC

Pressure Law

P = 0.0024T + 0.9006

0.98

1

1.02

1.04

1.06

1.08

1.1

1.12

0 10 20 30 40 50 60 70 80 90

Temperature/oC

Pre

ssu

re/1

05 P

a

Pressure Law Experiment 2

Results shown in textbook

Experiment set up from another textbook Larger range –

try this!

Caution!

The flask is

very hot!!!

What we found:

The pressure sensor doesn’t work??

Temperature variation

- can’t reach 150oC

- There is a change of at least 20oC

Explanation by supplier:

“The pressure sensor has to be put

in the same temperature

environment.”

Need another set up

TD-8595 Absolute

Zero Sphere

$2437

Laboratory in Your Pocket

Export to Excel

(teacher)

Copy data and plot graph

(student)

Temperature °C Pressure kPa

32.6 104.436

34.6 104.215

34.8 103.951

34.7 103.829

34.6 103.698

34.4 103.605

34.2 103.538

34.1 103.476

33.9 103.385

33.7 103.256

33.5 103.197

33.2 103.071

33.1 102.987

32.9 102.93

32.7 102.864

32.4 102.74

32.2 102.652

32.1 102.612

32 102.551

31.7 102.427

31.5 102.378

31.4 102.352

31.3 102.306

31.1 102.236

31 102.183

30.9 102.138

30.8 102.102

30.6 102.044

30.2 101.877

30.1 101.846

29.8 101.729

29.6 101.654

29.5 101.586

29.4 101.544

29.3 101.499

29.1 101.42

28.2 101.099

27.9 100.968

27.4 100.752

26.6 100.473

26.5 100.41

Pressure Law

P = 0.4043T + 89.657

100.5

101

101.5

102

102.5

103

103.5

104

25 27 29 31 33 35 37

temperature/o C

Pre

ssu

re/k

Pa

Larger temperature range

Absolute zero found: -221oC

P= 0.3962T + 89.893

102.5

102.6

102.7

102.8

102.9

103

103.1

31.8 32 32.2 32.4 32.6 32.8 33 33.2

Temperature/oC

Pre

ssu

re/k

Pa

Smaller temperature range

Absolute zero found: -227oC

Students’ results

Wrong measurements Did not wait till steady situations

Did not draw the best-fit line

Some students did not

know how to relate

with absolute zero.

Cannot distinguish

increase, increase

linearly, or proportional.

some students

even think that

pressing the can

into water

changes pressure

of air inside.

Some students

can correctly state

the relation and

find absolute zero

using correct

method.

Able to state

some errors.

Can’t tell the

difference

(probably because

they did not try that

experiment).

Suitable for SBA?

Skills

Fully immerse the can into water.

Use the data taken only after attaining

steady situation.

Check whether the can is air-sealed.

**Treatment of Data

Graph plotting (axes with labels, suitable

scale, best-fit straight line)

Find the x-intercept from the graph

Suitable for SBA?

Understanding

Some students can point out:

- there may be leakage of gas

- the volume of the can is small

- the range of temperature is small

- the temperature of air may not be uniform

- air does not obey pressure law (not dry)

- there is error in finding the intercept from the graph

Time needed

at most 30 minutes for experiment

suitable for completion within 1-lesson

Suitable for SBA?

Mark range

similar to other SBA experiments

can distinguish good/average/bad

performances

Thank you!