Transcript Calibration, Temperature Scales, Percent Error

Calibration,
Temperature &
Percent Error
What is Calibration?
calibration of any measuring device is:
distance between two closest lines
• NOT distance between two closest #’s
• NOT all same instruments calibrated
the same
not all
graduated
cylinders
calibrated
same way
Large graduated cylinder:
? capacity
? calibration
1000 ml
10 ml
? calibration
1 ml
meniscus falls between 67ml & 68ml
67.4 ml
? calibration
1 ml
13.0 ml
what about:
12.9 ml
?
13.1 ml
?
Can you figure the calibration of
any piece of lab equipment?
YES
meter stick: two closest lines
are 1 mm (millimeter) apart
? calibration
25 ml
quadruple
beam
balance
What’s the calibration?
183.599 g
183.600 g
0.01 g
183.601 g
meniscus between
21.3ml & 22.4ml
? calibration
0.1 ml
21.35 ml
BURET: unlike graduated cylinder, numbers
go down, so you read backwards compared to
way read graduated cylinder
Temperature
Scales
scientifically speaking …
the definition of temperature:
temperature is measure of average
kinetic energy of particles in system
comparing 3 different temperature scales
comparing 3 different scales
World’s Record Cold Temperatures
Date
˚F
˚C
World :
East Antarctica
Verkhoyansk, Russia (Siberia)
8/2010
2/7/1892
–135.8
–94
Asia:
Oimekon, Russia
2/6/1933
–90
–68
Greenland:
Northice
1/9/1954
–103
–75
No. America:
Snag, Yukon, Canada
2/3/1947
–81
–63
1/23/1971
1/20/1954
–80
–70
–62
–56.5
US:
Prospect Creek, Alaska
Rogers Pass, Montana
–94.7
–70
Conversion formulas
To convert between celsius & Kelvin scales:
K = °C + 273
(more precisely 273.15)
°C = K – 273
[F = (9/5 °C) + 32]
errors in science
experiments are
inevitable and need to
be dealt with …
Percent Error
ratio of error to accepted value
% error =
error
accepted value
x
100
Calculation of Error
measuredaccepted
value – accepted value x 100
value
absolute value: always positive
Data table
students asked to find density of sucrose
[sucrose has density of 1.59 g/cm3]
Student A
(g/cm3)
Student B
(g/cm3)
Student C
(g/cm3)
Trial 1
1.54
1.40
1.70
Trial 2
1.60
1.68
1.69
Trial 3
1.57
1.45
1.71
calc differences in density
Student A
(g/cm3)
Student B
(g/cm3)
Student C
(g/cm3)
Trial 1
0.05
0.19
0.11
Trial 2
0.01
0.09
0.10
Trial 3
0.02
0.14
0.12
Remember, error is always positive number
then calculate % error
Student A
% error
Student B
% error
Student C
% error
Trial 1
3.14
11.9
6.9
Trial 2
0.63
5.7
6.3
Trial 3
1.26
8.8
7.5
What can do with error?
• easy to compare data from one
student/group to another
• easy to compare data from one trial
to another
• can map change from one lab to
next or from start of year to end