Scientific Measurement Chapter 3 Scientific Measurement

Ch 3.1 The Importance of Measurement

Ch 3.1 The Importance of Measurement Qualitative Measurement – measurement that gives descriptive nonnumeric results Example: Feel some ones head to see if they are running a fever or not Quantitative Measurement – measurement that gives definite usually numeric results Example: Measure some ones temperature with a thermometer

Scientific Notation Used to write small or large numbers N x 10n N = a number between 1 and 10 n = a positive or negative integer

Scientific Notation Mass of an atom of gold 3.27 x 10-22g Number of hydrogen atoms in 1g 602000000000000000000000 6.02 x 1023 atoms

Coefficient Scientific notation has three parts to it: the coefficient, base, and exponent

Scientific Notation: Multiply and Divide Multiply coefficients and add exponents (3.0 x 104) x (2.0 x 102) = 6.0 x 106 Divide coefficients and subtract exponents (3.0 x 104) / (2.0 x 102) = 1.5 x 102

Scientific Notation: Addition and Subtraction Make the exponents the same, then add or subtract 3.0 x 104 + 2.0 x 102 = 300.0 x 102 + 2.0 x 102 = 302.0 x 102

Chapter 3.2 Uncertainity

Accuracy and Precision Accuracy – how close a measurement is to the true value of the quantity measured Precision – how closely two or more measurements of the same quantity agree with one another

Accuracy and Precision A student was asked to measure the length of the hallway. He came up with the following lengths. 10.2m, 10.1m, 10.2m The actual length was 12.5m. How would you describe his results?

Accuracy and Precision A student was asked to determine the mass of a beaker. She came up with 34.8g, 34.7g and 34.7g. The actual mass was 34.8g. How would you describe her results?

Percent Error % Error = accepted value – experimental value x 100 The correct answer Your answer The correct answer

Percent Error A student was asked to determine the mass of a beaker. She came up with an average mass of and 34.7g. The actual mass was 34.8g. What is the percent error? 34.8 g –34.7 g x 100 = 0.287 % Error 34.8

Significant Figures Abbreviation: sig fig Why are sig figs so IMPORTANT?

Significant Figures 1) Any digit that is not zero is significant 24.7 meters 3 sig figs 0.743 meters 3 sig figs 74 grams 2 sig figs

Significant Figures 2) Zeros between nonzero digits are significant 7003 mL 4 sig figs 40.7 cm 3 sig figs 1.5035 g 5 sig figs

Significant Figures 3) Zeros to the left of the first nonzero digits are not significant 0.0071 km 2 sig figs 0.420 g 3 sig figs 0.00009999 L 4 sig figs

Significant Figures 4) If a number is greater that 1, then all the zeros written to the right of the decimal point count as significant 43.00 m 4 sig figs 1.0100 mg 5 sig figs 9.00 cL 3 sig figs

Significant Figures 5) Numbers without a decimal, the trailing zeros may or may not be significant. It will depend on other information in the problem. 5,000 1 or 4 sig figs 68,900 3 or 5 sig figs 52,010,000 4 or 8 sig figs

Significant Figures 6) Unlimited significant figures when: - Counting an exact number (whole number only) such as number of people in the class - Exactly defined quantities 60 minutes = 1 hour

Significant Figures for Calculations Addition and Subtraction: The answer can not have more digits to the right of the decimal point than either original number. (Least number of decimal places) 400.567 + 21.0 = 421.567 421.6 68.892 – 48.47 = 20.422 20.42

Significant Figures for Calculations Multiplication and Division: The number of significant figures in the final product or quotient is determined by the original number with the smallest number of significant figures. 12,003 x 45 = 1,525÷ 30.1 = 540,135 50.66445183 540,000 50.7

Chapter 3.3 SI Units International System of Units From the French: Le Systeme International d’Unites

energy, work, quantity of heat SI Units Symbol Name Quantity m meter length g gram mass Pa pascal pressure K kelvin temperature mol mole amount of a substance J joule energy, work, quantity of heat s second time

solution concentration SI Units (continued) min minute time h hour d day y year L liter volume ppm parts per million concentration M molarity solution concentration u atomic mass unit atomic mass

Prefixes with SI Units Prefix Symbol Meaning tera- T 1,000,000,000,000 or 1012 giga- G 1,000,000,000 or 109 mega- M 1,000,000 or 106 kilo- K 1,000 or 103 hecto- H 100 or 102 deca- D 10 or 101 BASE m, L, g, …. Any base unit deci- d 1/10 or 10-1 centi- c 1/100 or 10-2 milli- m 1/1,000 or 10-3 micro- μ 1,000,000 or 10-6 nano- n 1,000,000,000 or 10-9 pico- p 1,000,000,000,000 or 10-12

How to remember the basic metric prefixes? Mnemonics :These stand for the Metric prefixes and base unit. kilo hecto deca base deci centi milli Kittens Hate Dogs Because Dogs Cant Meow Kangaroos Hop Down My Driveway Christmas Morning Kings Hate Dragons Because Dragons Can’t Make Money King Henry Died Bloated Drinking Chocolate Milk Kangaroos Hop Down Mountains Drinking Chocolate Milk

giga mega kilo hecto deca BASE deci centi milli micro nano pico King Henry Danced Merrily Down Center Main Meeting Nice People Great Mighty King Henry Died By Drinking Chunky Milk Good Models Know How Dunkin Donuts Can Make U Not Petit

Chapter 3.4 Density Density = Mass / Volume d = m/v 1 g/cm3 = 1 g/ml 1 mL = 1 cm3

Density Column

Chapter 3.5 Temperature Scales 0C = K – 273 K = 0C + 273 Freezing 00C = 273K Boiling 1000C = 373K Absolute Zero O K

Temperature Scales