Scientific M

easurement

Chapter 3

Chapter 3.1 - M

easurements and

Their Uncertainty

Measurem

ent: A quantity that

has both a number and a unit.

-It is important to m

ake m

easurements and decide

whether a m

easurement is

correct.

-International System of

Units (SI)

Scientific Notation: A

given num

ber is written as the product of

two num

bers.

Ex: 10

x

Ex

2: 1023 = ?

Accuracy vs. Precision

Accuracy: M

easure of how close

a measurem

ent comes to the

actual or true value of whatever

is measured.

Precision: Measure of how

close a series of m

easurements are to

one another.

To evaluate the accuracy of a m

easure, the measured value

must be com

pared to the correct value.

To evaluate the precision of a m

easurement, you m

ust com

pare the values of two or

more repeated m

easurements.

Determ

ining Error:

Accepted Value: C

orrect value based on reliable references

Experimental Value: V

alue based on reliable references

Error = experimental value -

accepted value

Percent Error = error/accepted value X

100%

Significant Figures: Measurem

ent include all of the digits that are know

n, plus a last digit that is estim

ated.

Measurem

ents must alw

ays be reported to the correct num

ber of significant figures because calculated answ

ers often depend on the num

ber of significant figures in the values used in the calculation.

3.2 International System

of Units

SI Units: m

eter, kilogram, kelvin,

second and mole.

Kelvin: C

0 +273

Celsius: K

-273

Energy: the capacity to do work

-M

easured in joules.-

1 J =.2390 cal-

1 cal = 4.184 J

3.3 Conversion Problem

s

Conversion Factor: A

ratio of equivalent m

easurements.

-1 cm

= 1m-

1$ = 4 Quarters = ? D

imes =

? Nickels = ? Pennies

Dim

ensional Analysis: A

way to

analyze and solve problems

using units, or dimensions, of

the measurem

ents.

Ex: Daily problem

solving

Converting U

nits:

Analyze- List the know

ns and unknow

ns

Calculate- Solve for the

unknowns

Evaluate- Does that m

ake sense?

Density: ratio of an object’s m

ass to its volum

e.

-M

ass/volume

●A

n intensive property that depends only on the com

position of a substance, not on the size of the sam

ple.

●A

s the density of an object generally decreases the tem

perature increases.