1. INTERNATIONAL SYSTEM (SI) OF MEASURE

2. 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

3. ACCURACY AND PRECISION

4. TRUE VALUE – quantity use 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

5. ACCURATE AND PRECISE

6. NOT ACCURATE NOT PRECISE

7. PRECISE NOT ACCURATE

8. SIGNIFICANT FIGURES 4.6 cm 4.58 cm 3.0 cm NOT 3 cm
All the numbers that you are sure of plus an estimated number
4.6 cm
4.58 cm
3.0 cm NOT
3 cm

9. RULES IN DETERMINING SIGNIFICANT FIGURES (sf)
1. All non-zero digits are significant.
Ex. 432 – 3 sf – 4 sf
2. Zeroes in between significant figures are significant (SANDWICH RULE).
Ex – 4 sf – 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 – 4 sf
0.001 – 1 sf – 9 sf

10. 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
7.111
1.00
0.9 1
0.9
0.9 1
7.1

11. 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.
3 sf
2 sf
1.11 X
3 sf
1 sf
1.11 X
5.5
÷ 1
2 sf
1 sf
1.1
2 sf 6
1 sf 1
1 sf

12. PERCENTAGE ERROR Example : Actual value = 100.0
Obtained using the following steps:
Determine the absolute value of the difference between the actual value and the measured value.
Divide the difference by the actual value.
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
= / – / X 100% = 1.20 %
100