Calibration, Temperature & Percent Error

What is Calibration?

calibration of any measuring device is: distance between two closest two closest lineslines

• NOTNOT distance between two closest #’s

• NOT all same instruments calibrated the same

not all graduated cylinders calibrated same way

Large graduated cylinder:

? ? capacitycapacity

?? calibration calibration

1000 1000 mlml

10 ml10 ml

? calibration ? calibration 1 ml1 ml

67.4 ml

meniscus falls between 67ml & 68ml

? calibration ? calibration 1 ml1 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? calibration

25 ml25 ml

quadruple beam balance

What’s the calibration? 0.01 g

183.599 g 183.600

g

183.601 g

meniscus between 21.3ml & 22.4ml ? calibration

0.1 ml0.1 ml

BURET: unlike graduated cylinder, numbers go down, so you read backwards compared to way read graduated cylinder

21.35 ml

TemperatureScales

scientifically speaking …

the definition of temperature:

temperature is measure of average kinetic energy of particles in system

comparing 3 different scales

comparing 3 different temperature scales

World’s Record Cold Temperatures Date ˚F ˚C

World : East Antarctica 8/2010 –135.8 –94.7Verkhoyansk, Russia(Siberia) 2/7/1892 –94 –70

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

US: Prospect Creek, Alaska 1/23/1971 –80 –62Rogers Pass, Montana 1/20/1954 –70 –56.5

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 x 100 accepted value

Calculation of Error

measured value – accepted value x 100 accepted value

absolute value: always absolute value: always positivepositive

Data tableData table

1.711.451.57Trial 3

1.691.681.60Trial 2

1.701.401.54Trial 1

Student C

(g/cm3)

Student B

(g/cm3)

Student A

(g/cm3)

students asked to find density of sucrose [sucrose has density of 1.59 g/cm3]

calc differences in densitycalc differences in density

0.120.140.02Trial 3

0.100.090.01Trial 2

0.110.190.05Trial 1

Student C

(g/cm3)

Student B

(g/cm3)

Student A

(g/cm3)

Remember, error is always positive numberRemember, error is always positive number

then calculate % errorthen calculate % error

7.58.81.26Trial 3

6.35.70.63Trial 2

6.911.93.14Trial 1

Student C

% error

Student B

% error

Student A

% error

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