SCIENTIFIC MEASUREMENT CHAPTER 3 SCIENTIFIC MEASUREMENT

QUALITATIVE MEASUREMENTS GIVE RESULTS IN A DESCRIPTIVE, NON-NUMERIC 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/m3 10 ft. 3 ft. A QUANTITATIVE MEASUREMENT IS ONLY AS ACCURATE AS THE INSTRUMENT AND METHOD USED TO TAKE THE MEASUREMENT.

INTERNATIONAL SYSTEM of UNITS Units of Measurement Quantity SI base unit or derived unit Symbol Length meter m Volume cubic meter m3 Mass kilogram kg Density grams per cubic centimeter g/cm3 Temperature kelvin K Time second s Pressure pascal Pa Energy joule J Amount of Substance mole mol Luminous Intensity candela cd Electric Current ampere a

ACCURACY and PRECISION ACCURACY – MEASURE OF CLOSENESS TO TRUE VALUE PRECISION – THE CLOSENESS IN A SERIES OF MEASUREMENTS

SIGNIFICANT FIGURES (SF’s) SF’s INCLUDE ALL KNOWN DIGITS PLUS 1 LAST DIGIT THAT IS ESTIMATED. CALCULATED VALUES DEPEND ON SF’s IN VALUES USED IN CALCULATION.

2007 and 15.08 both have 4 SF’s SIGNIFICANT FIGURES WHAT ARE SIGNIFICANT? EVERY NON-ZERO DIGIT ZEROS BETWEEN NON-ZERO NUMBERS 2007 and 15.08 both have 4 SF’s

41.00 and 10.60 each have 4 significant figures. WHAT ARE SIGNIFICANT? ZEROS AT THE END OF A NUMBER & ARE AFTER A DECIMAL POINT 41.00 and 10.60 each have 4 significant figures.

Number of red M&M’s SIGNIFICANT FIGURES WHAT ARE SIGNIFICANT? EXACT NUMBERS HAVE UNLIMITED SF’s. Number of red M&M’s

SIGNIFICANT FIGURES WHAT ARE NOT SIGNIFICANT? ZEROS IN FRONT OF NON-ZERO NUMBERS ZEROS AT THE END OF A NUMBER WITHOUT A DECIMAL POINT 0.00079 and 650,000 each have 2 significant figures.

ADD and SUBTRACT SIGNIFICANT FIGURES ANSWER MUST HAVE SAME NUMBER OF DECIMAL PLACES AS THE VALUE WITH THE LEAST NUMBER OF DECIMAL PLACES

ADD and SUBTRACT SIGNIFICANT FIGURES 57.7456 4 decimal places 59.5846 need to round to 3 decimal places: 59.585

SIGNIFICANT FIGURES 17.57 m + 8.4 m + 13.675 m = ? 14 cm + 0.57 cm + 1.865 cm = ? 13.2 Pa– 1.25 Pa = ? 273.5oK – 26.5oK = ?

MULTIPLY & DIVIDE SIGNIFICANT FIGURES ANSWER MUST HAVE THE SAME NUMBER OF SF’s AS THE VALUE WITH THE LEAST NUMBER OF SF’s

MULTIPLY & DIVIDE 15.375 ÷ 5.0 = 3.075 5 2 SIGNIFICANT FIGURES NUMBER OF SF’s 5 2 ROUND TO 3.1

SIGNIFICANT FIGURES 8.654 m x 0.34 m = ? 2.10 cm x 0.50 cm = ? 10.4815 ml ÷ 8.4 ml = ? 0.365 m ÷ 0.050 m = ?

SCIENTIFIC NOTATION IS USED TO HANDLE THE RANGE OF VALUES NUMBERS & MEASUREMENT CHEMISTRY INVOLVES ACCURATE MEASUREMENTS THAT RANGE FROM VERY LARGE TO VERY SMALL SCIENTIFIC NOTATION IS USED TO HANDLE THE RANGE OF VALUES

SCIENTIFIC NOTATION VALUES ARE WRITTEN AS A PRODUCT OF 2 NUMBERS COEFFICIENT – VALUE BETWEEN 1 & 10 EXPONENT - 10 RAISED TO A POWER THE EXPONENT INDICATES THE NUMBER OF TIMES THAT THE COEFFICIENT IS MULTIPLIED OR DIVIDED BY 10

SCIENTIFIC NOTATION 175.983 0.9600000 3.65 x 10-3 7.5 x 106 WHAT ARE THESE VALUES IN SCIENTIFIC NOTATION? 6,954,000 0.0078654 175.983 0.9600000 WHAT ARE THESE VALUES IN STANDARD NUMERICAL FORM? 3.65 x 10-3 7.5 x 106 1.865 x 102 8.75 x 10-5

MULTIPLY COEFFICIENTS SCIENTIFIC NOTATION MULTIPLICATION MULTIPLY COEFFICIENTS ADD EXPONENTS 7.2 x 102 · 5.02 x 10-3 = ? 1.0 x 102 · 2.6 x 108 = ?

SUBTRACT EXPONENT OF DENOMINATOR FROM EXPONENT OF NUMERATOR SCIENTIFIC NOTATION DIVISION DIVIDE COEFFICIENTS SUBTRACT EXPONENT OF DENOMINATOR FROM EXPONENT OF NUMERATOR 8.4 x 103 / 2.1 x 10-2 = ? 7.25 x 104 / 5.0 x 102 = ?

ADDITION & SUBTRACTION SCIENTIFIC NOTATION ADDITION & SUBTRACTION ADJUST EXPONENT OF BOTH NUMBERS TO BE SAME ADJUST COEFFICIENT TO REFLECT CHANGE IN EXPONENT PERFORM OPERATION AND READJUST ANSWER TO PROPER SCIENTIFIC NOTATION

SCIENTIFIC NOTATION 7.563 x 102 - 1.77789 x 10-3 = ?

DENSITY Which is heavier – a pound of popcorn or a pound of cheese? They would have the same mass!! However, if you had equal VOLUMES of popcorn and cheese, the cheese would have more mass.

IS IT MORE OR LESS DENSE THAN WATER? SPECIFIC GRAVITY SPECIFIC GRAVITY (Sp.G.) COMPARES THE DENSITY OF 1 MATERIAL TO THE DENSITY OF WATER. DENSITY OF WATER @ 4o C = 1 g/cm3, AND IS USED AS A REFERENCE. LIQUID SPECIFIC GRAVITY IS MEASURED BY A HYDROMETER. IF Sp.G. OF WOOD = 0.5, IS IT MORE OR LESS DENSE THAN WATER?

THE TEMPERATURE OF AN OBJECT DETERMINES THE FLOW OF HEAT TRANSFER HOTTER COOLER CELCIUS (CENTIGRADE) scale uses the freezing point of water as 0oC and the boiling point of water as 100oC. KELVIN scale uses 273oK for the freezing point of water, and 373oK as the boiling point.