Chapter 2 Measurements and Calculations

Sect. 2-1: Scientific Method Scientific Method Scientific Method ▫ Observing and collecting Data ▫ Qualitative and Quantitative ▫ Formulating Hypothesis ▫ Testing hypothesis ▫ Theorizing

Model Model Theory Theory

Sect. 2-2: Units of Measurement SI Measurement SI Measurement ▫ Le Systéme International d’Unités (International System of Units)

7 SI Base Units Mass – kilogram (kg) Mass – kilogram (kg) Length – meter (m) Length – meter (m) Time – second (s) Time – second (s) Temperature – Kelvin (K) Temperature – Kelvin (K) Amount of substance – mole (mol) Amount of substance – mole (mol) Electric current – ampere (A) Electric current – ampere (A) Luminous intensity – candela (cd) Luminous intensity – candela (cd)

SI Prefixes See page 35 in textbook See page 35 in textbook

Derived SI units Volume Volume ▫ Cubic meter (m 3 ) is very large, so cubic centimeters (cm 3 ) is usually used instead ▫ cm 3 is equal to one mL, so they can be used interchangeably.

Density Density ▫ D=mass/volume ▫ Units typically used are g/cm 3 or g/mL

Conversion Factors Ratio derived from the equality of 2 different units Ratio derived from the equality of 2 different units used to convert from one unit to the other used to convert from one unit to the other Ex.: 1 min or 60 sec Ex.: 1 min or 60 sec 60 sec 1 min 60 sec 1 min

How many seconds are in 5 minutes? How many seconds are in 5 minutes? (Work problem by using dimentional analysis/conversion factors.) 5.712g is equal to how many milligrams? 5.712g is equal to how many milligrams?

Sect. 2-3: Using Scientific Measurements Accuracy vs. Precision Accuracy vs. Precision /20/unit01_kinematicsdynamics/chp02_intro/lesson02.htm&h=176&w=178&sz=2&hl=en&start=8&tbnid=- MXNdAPx2LHv8M:&tbnh=100&tbnw=101&prev=/images%3Fq%3Ddart%2Bboard%2Baccuracy%2Band%2Bprecision%26gbv%3D2%26svnum%3D10%26hl%3Den

Percent Error % error =Accepted-Experimental x 100 % error =Accepted-Experimental x 100Accepted Some error in measurements can be expected due to precision of instruments Some error in measurements can be expected due to precision of instruments

Significant figures Sig figs are based on instrument precision (numbers can only be as exact as the instrument is) Sig figs are based on instrument precision (numbers can only be as exact as the instrument is)

Rules for Sig figs : Rules for Sig figs : –Skip over zeroes at the side you start counting on –If it has a decimal, count from the left –If it doesn’t have a decimal, count from the right –Once you start counting, count everything (even zeroes)

Example : Example : How many sig figs are in the number ? 5 sig figs 5 sig figs

Example : How many sig figs are in the number 5,400? Example : How many sig figs are in the number 5,400? 2 sig figs 2 sig figs

Rounding with Sig Figs When adding/subtracting, answer will be rounded to least number of decimal places When adding/subtracting, answer will be rounded to least number of decimal places When multiplying/dividing, answer will be rounded to least number of sig figs When multiplying/dividing, answer will be rounded to least number of sig figs

When using conversion factors, refer to the “given” number to determine number of sig figs for the answer When using conversion factors, refer to the “given” number to determine number of sig figs for the answer

Scientific Notation Convert to scientific notation Convert to scientific notation 8.72 x x 10 -4

Convert to scientific notation. Convert to scientific notation x x 10 5

Scientific Notation by using the calculator Use “EE” or “exp” key on your calculator to replace “ x 10^” Use “EE” or “exp” key on your calculator to replace “ x 10^” Ex: 8.72 x would be 8.72”EE”-4 Ex: 8.72 x would be 8.72”EE”-4

Direct Proportions Dividing two quantities by each other gives a constant value Dividing two quantities by each other gives a constant value =3&hl=en&start=1&tbnid=ht5Oe573XV4IDM:&tbnh=83&tbnw=114&prev=/images%3Fq%3Ddirect%2Brelationship%2Bgraph%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DG

Inverse Proportions Multiplying two quantities by each other gives a constant value Multiplying two quantities by each other gives a constant value =3&hl=en&start=1&tbnid=ht5Oe573XV4IDM:&tbnh=83&tbnw=114&prev=/images%3Fq%3Ddirect%2Brelationship%2Bgraph%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DG