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

ACCURACY AND PRECISION

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

ACCURATE AND PRECISE

NOT ACCURATE NOT PRECISE

PRECISE NOT ACCURATE

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

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

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 1.00 - 0.1 0.9 1 - 0.1 0.9 0.9 1 7.1

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. 3 sf 2 sf 1.11 X 1 3 sf 1 sf 1.11 X 1.0 5.5 ÷ 1 2 sf 1 sf 1.1 2 sf 6 1 sf 1 1 sf

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 = / 100.0 – 101.2 / X 100% = 1.20 % 100