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1.3 Units
of Measurement
·
measurements: consist of a number and a scale
·
SI system:
internationally accepted system of measurement
1 dm
3
= (10cm)
3
= 1 L
1 cm
3
= 1 mL
mass:
measure of an objects resistance to a change in its state of motion
F = m * a
F= weight (force)
m= mass
a= acceleration due to gravity
micro
nano
(u)
(n)
.000001
.0000001
mega
kilo
hecto
(M)
(K)
(h)
(da)
100,000
1,000
100
10
10
6
10
3
10
2
deka
base
deci
centi
milli
unit
(d)
(c)
(m)
1
.1
.01
.001
10'
10
0
10
1
10
2
10
3
10
6
10
9
1.4 Uncertainty in Measurement
measurement always has some degree of uncertainty (depends on the precision of the
measuring device)
·
significant figures:
certain digits and the first uncertain digit in a measurement
(uncertainty in last digit is assumed to be + 1)
Example:
25
mL
25 + 1 mL
measurement
between
24 & 26 mL
25.00
25.00 + 0.01 mL
measurement
between
24.99 and 25.01 mL
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Leading zeros aren't significant
3.
Captive.
..
significant
4.
Trailing zeros
(w/o
decimal point) not significant
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 Spring '10
 McOmber
 Chemistry

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