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ACCURACY AND PRECISION
TRUE VALUE – quantity used by general
agreement of the scientific community
ACCURACY- closeness of the
measurements to the true value of what
is being measured
PRECISION – closeness of the
measurements to one another
ACCURATE AND PRECISE
NOT ACCURATE NOT PRECISE
PRECISE NOT ACCURATE
SIGNIFICANT FIGURES
All the numbers that you are sure of plus an
estimated number
4.6 cm
4.58 cm
3.0 cm NOT
3 cm
RULES IN DETERMINING
SIGNIFICANT FIGURES (sf)
1. All non-zero digits are significant.
Ex. 432 – 3 sf
2238 – 4 sf
2. Zeroes in between significant figures are
significant (SANDWICH RULE).
Ex. 1001 – 4 sf
3 000 006 – 7 sf
3. Zeroes to the right of a significant figure and to
the right of the decimal point are significant
(DOUBLE RIGHT).
Ex. 100 – 1 sf
100.0 – 4 sf
0.001 – 1 sf
10.000 001 0 – 9 sf
EXAMPLES
453 kg
5057 L
5.00 cm
NUMBER OF
SIGNIFICANT
FIGURES
3
4
3
COMMENT
All non-zero digits are always
significant.
Zeros between 2 significant
figures are significant.
(SANDWICH RULE)
For the zero on the rightmost
position, zeroes to the right of the
decimal point are significant.
Zeroes in between significant
figures are significant.
Placeholders are not significant
500 s
1
ADDITION AND SUBTRACTION
OF SIGNIFICANT FIGURES
The sum or difference of the numbers should
have the same number of decimal places as
the quantity with the lowest decimal places.
5.0
+ 2.111
7.111
7.1
1.00
- 0.1
0.9
0.9
1
- 0.1
0.9
1
MULTIPLICATION AND DIVISION
OF SIGNIFICANT FIGURES
The product or quotient of the numbers should have
the same number of significant figures as the
quantity with the lowest number of significant
figures.
1.11 3 sf
X
1
1.11
1
1 sf
3 sf
1 sf
1.11
X 1.0
1.11
1.1
3 sf
2 sf
3 sf
2 sf
5.5
÷ 1
5.5
6
2 sf
1 sf
2 sf
1 sf
PERCENTAGE ERROR
Obtained using the following steps:
1.
Determine the absolute value of the difference
between the actual value and the measured value.
2.
Divide the difference by the actual value.
3.
Multiply by 100 % to obtain percentage error.
Example : Actual value = 100.0
Measured value is 101.2
% Error = /Actual value-measured value/ x 100%
actual value
= / 100.0 – 101.2 / X 100% = 1.20 %
100
INTERNATIONAL
SYSTEM (SI) OF
MEASURE
SI BASE UNITS
QUANTITY
UNIT
SYMBOL
Length
meter
m
Mass
kilogram
kg
Time
second
s
Amount of substance
mole
mol
Current
ampere
A
Temperature
kelvin
K
Luminous intensity
candela
cd
NUMERICAL PREFIXES
FACTOR PREFIX
SYMBOL FACTOR PREFIX
SYMBOL
10 18
exa
E
10 -1
deci
d
10 15
peta
P
10 -2
centi
c
10 12
tera
T
10 -3
milli
m
10 9
giga
G
10 -6
micro
u
10 6
mega
M
10 -9
nano
n
10 3
kilo
k
10 -12
pico
p
10 2
hecto
h
10 -15
femto
f
10 1
deka
da
10 -18
atto
a
CONVERSION OF UNITS
(Ex) 100 m = ___________ mm
100 m = (100 m) (10 dm) (10cm) (10 mm )
1m
dm
cm
= 100 000 mm
FORMULA TRANSFORMATION
Given the formula: 3A + B = Z,
solve for A
3A + B -B = Z -B
3A = Z - B
3
3
A = Z-B
3
IMPORTANCE OF FORMULA
TRANSFORMATION