Transcript Lesson 3 Scientific Measurement

Unit 1
Scientific Measurement
Homework
Read pages 11-13
HW: Unit 1 Significant Figures
Quiz: October 1st or 2nd
Qualitative Measurements
Give results in a descriptive, nonnumeric form:
hot
cold
big
little
heavy
light
short
tall
Qualitative measurements are often
influenced by the measurer’s perception.
Quantitative Measurements
Give results in a definite form, typically a
number with units:
100 °C
32 °F
10 gal.
30 ml
11.4 g/cm3
0.5 g/cm3
10 ft.
3 ft.
A quantitative measurement is only as
accurate as the instrument and method used
to take the measurement.
Accuracy and Precision
Accuracy - a measure of
how close a measurement
is to the true value of
whatever is being
measured
 Precision – a measure of
how close a series of
measurements are to one
another

Significant Figures

In Mathematics all numbers are exact; for
example: 1 = 1.00 = 1.000000

In Science, numbers that are from data that is
measured or calculated from measurements,
are limited in the number of significant figures
they can use. 1 ≠ 1.00 ????
Significant figures

The significant figures in a measurement
include all of the digits that are known.

Calculated values depend on the number of
significant figures in the values used in the
calculations.
Significant Figures
For Example:

Using a meter stick, that has markings 1mm
apart, to measure the diameter of a can you
might get 38 mm.
 Using calipers, that read to .01 mm, to
measure the same can, you might get 37.79
mm.
 The caliper measurement has more significant
figures than the meter stick measurement.
Significant figures
Rules of significant figures:

Any nonzero digit (1,2,3,4,5,6,7,8,9) is
significant.
Example: 23.5 has 3 significant figures
 Any zero that is sandwiched in between two
nonzero digits is significant.
Examples: 3200.04 has 6 significant figures
403.2 has 4 significant figures
Significant figures

Zeros in front of non-zero numbers are not
significant.

Zeros at the end of a number without a
decimal point are not significant
Examples: 0.00079 and 650,000 each have 2
significant figures.
Significant figures

A zero to the right of the rightmost nonzero
digit :
a) Is significant if there is a decimal anywhere in
the number.
Examples: 0.0000000040 has 2 significant
figures 973.4000 has 7 significant figures
b) Is not significant if there is no decimal in the
number.
Examples: 10,000 has 1 significant figure
5960 has 3 significant figures
Significant figures
Some numbers are exact numbers, and
have an infinite amount of significant
figures.
 Example: Integers, the results of
counting, are exact. 2 whole apples,
means exactly 2, or 2.0000000000... to
infinity.

Significant Figures
Some numbers can only be expressed
with scientific notation!!!
 Example: Express 1000 with 2 significant
figures.
 1000 – has only 1 sig. fig.
 1000.- has 4 sig. figs.
 1.0 x 10³ has 2 sig. figs.
Unit 1 – Sig Figs
2a. qual
b. qual
c. quant
d. both
3. Lisa – not accurate or precise
Lamont – accurate and precise
Leigh Ann – precise, not accurate
4a. 3
b. 2
c. 4
d. 4
e. 3
f. 3
5a. 98.5 L
b. 0.000763 cg
c. 57.0 m
d. 0.00750 mm