2 Types of measurement Quantitative- (quantity) use numbers to describe Qualitative- (quality) use description without numbers4 metersextra largeHot100ºCQuantitativeQualitativeQualitativeQuantitative
3 Which do you Think Scientists would prefer Quantitative- easy checkEasy to agree upon, no personal biasThe measuring instrument limits how good the measurement is
4 How good are the measurements? Scientists use two word to describe how good the measurements areAccuracy- how close the measurement is to the actual valuePrecision- how well can the measurement be repeated
5 DifferencesAccuracy can be true of an individual measurement or the average of severalPrecision requires several measurements before anything can be said about itexamples
11 Reporting Error in Experiment A measurement of how accurate an experimental value is(Equation) Experimental Value – Accepted ValueExperimental Value is what you get in the labaccepted value is the true or “real” valueAnswer may be positive or negative
12 | experimental – accepted value | x 100 Reporting Error in Experiment% Error =| experimental – accepted value | x 100accepted valueOR | error| x 100Answer is always positive
13 Example: A student performs an experiment and recovers 10.50g of NaCl product. The amount they should of collected was 12.22g on NaCl.Calculate ErrorError = g g= gCalculate % Error% Error = | -1.72g | x 10012.22g= % error
14 Convert to Scientific Notation And Vise Versa Example: 2.5x10-4 (___) is the coefficientand ( ___) is the power of ten2.5-4Convert to Scientific Notation And Vise Versa= ____________3.44 x = ____________2.16 x 103 = ____________= ____________5.5 x 1060.034421601.75 x 10-3
15 Multiplying and Dividing Exponents using a calculator (3.0 x 105) x (3.0 x 10-3) = _________________(2.75 x 108) x (9.0 x 108) = ________________(5.50 x 10-2) x (1.89 x 10-23) = ____________(8.0 x 108) / (4.0 x 10-2) = ________________9.00 x 1022.475 x 10171.04 x 10-242.0 x 1010
16 Adding and Subtracting Exponents using a calculator 7.5 x x 109 = __________________5.5 x x 10-5 = _________________5.498 x 10-2
17 Significant figures (sig figs) How many numbers mean anythingWhen we measure something, we can (and do) always estimate between the smallest marks.4.5 inches21345
18 Significant figures (sig figs) Scientist always understand that the last number measured is actually an estimate4.56 inches12345
19 Sig FigsWhat is the smallest mark on the ruler that measures cm?142 cm?140 cm?Here there’s a problem does the zero count or not?They needed a set of rules to decide which zeroes count.All other numbers do countTenths placeOnes placeYikes!
20 Which zeros count?Those at the end of a number before the decimal point don’t count12400If the number is smaller than one, zeroes before the first number don’t count0.045= 3 sig figs= 2 sig figs
21 Which zeros count? Zeros between other sig figs do. 1002 zeroes at the end of a number after the decimal point do countIf they are holding places, they don’t.If they are measured (or estimated) they do= 4 sig figs= 6 sig figs
22 Sig Figs Only measurements have sig figs. Counted numbers are exact A dozen is exactly 12A a piece of paper is measured 11 inches tall.Being able to locate, and count significant figures is an important skill.
23 Sig figs. How many sig figs in the following measurements? 458 g
24 Sig Figs. 405.0 g 4050 g 0.450 g 4050.05 g 0.0500060 g = 4 sig figs
25 Question 50 is only 1 significant figure if it really has two, how can I write it?A zero at the end only counts after the decimal place.Scientific notation5.0 x 101now the zero counts.50.0= 3 sig figs
26 Adding and subtracting with sig figs The last sig fig in a measurement is an estimate.Your answer when you add or subtract can not be better than your worst estimate.have to round it to the least place of the measurement in the problem
27 For example27.936.4+First line up the decimal places27.936.4+27.936.4Find the estimated numbers in the problemThen do the adding34.33This answer must be rounded to the tenths place
28 Rounding rules look at the number behind the one you’re rounding. If it is 0 to 4 don’t change itIf it is 5 to 9 make it one biggerround to four sig figsto three sig figsto two sig figsto one sig fig= 45.46= 45.5= 45= 50
29 Practice= = 11.76.0 x x 1036.0 x x 10-3= = 615= = 2.118= 3198 = 3.2 x 103= 2.12 = 2.1= = 6.2= 374= = 5.6 x 10-2
30 Multiplication and Division Rule is simplerSame number of sig figs in the answer as the least in the question3.6 x 6532350.83.6 has 2 s.f. 653 has 3 s.f.answer can only have 2 s.f.2400
32 The Metric System Easier to use because it is …… a decimal system Every conversion is by some power of ….10.A metric unit has two partsA prefix and a base unit.prefix tells you how many times todivide or multiply by 10.
33 Base Units Length - meter more than a yard - m Mass - grams - a bout a raisin - gTime - second - sTemperature - Kelvin or ºCelsius K or CEnergy - Joules- JVolume - Liter - half f a two liter bottle- LAmount of substance - mole - mol
34 Prefixes Kilo K 1000 times Hecto H 100 times Deka D 10 times deci d 1/10centi c 1/100milli m 1/1000kilometer - about 0.6 milescentimeter - less than half an inchmillimeter - the width of a paper clip wire
35 ConvertingKHDdcmKing Henry Drinks (basically) delicious chocolate milkhow far you have to move on this chart, tells you how far, and which direction to move the decimal place.The box is the base unit, meters, Liters, grams, etc.
36 k h D d c m Conversions 5 6 Change 5.6 m to millimeters starts at the base unit and move three to the right.move the decimal point three to the right56
37 k h D d c m Conversions convert 25 mg to grams convert 0.45 km to mm convert 35 mL to litersIt works because the math works, we are dividing or multiplying by 10 the correct number of times (homework)= g= 450,000 mm= L
38 Volume calculated by multiplying L x W x H Liter the volume of a cube 1 dm (10 cm) on a sideso 1 L =10 cm x 10 cm x 10 cm or 1 L = 1000 cm31/1000 L =1 cm3Which means 1 mL = 1 cm3
39 Volume 1 L about 1/4 of a gallon - a quart 1 mL is about 20 drops of water or 1 sugar cube
40 Mass weight is a force, Mass is the amount of matter. 1gram is defined as the mass of 1 cm3 of water at 4 ºC.1 ml of water = 1 g1000 g =1000 cm3 of water1 kg = 1 L of water
41 Mass 1 kg = 2.5 lbs 1 g = 1 paper clip 1 mg = 10 grains of salt or 2 drops of water.
42 Density how heavy something is for its size the ratio of mass to volume for a substanceD = M / VMDV
43 Density is a Physical Property The density of an object remains _________ at _______ ________Therefore it is possible to identify an unknown by figuring out its density.Story & Demo (king and his gold crown)constantconstanttemperature
44 What would happen to density if temperature decreased? As temperature decreases molecules______ _____And come closer together therefore making volume _________The mass ______ ____ _______Therefore the density would _______Exception _____________________Therefore Density decreases ICE FLOATSslowdowndecreaseSTAYSTHESAMEINCREASEWATER, because it expands.
45 Units for Density1. Regularly shaped object in which a ruler is used. ______2. liquid, granular or powdered solid in which a graduated cylinder is used ______3. irregularly shaped object in which the water displacement method must be used _____g/cm3g/mlg/ml
46 Sample Problem:What is the density of a sample of Copper with a mass of 50.25g and a volume of 6.95cm3?D = M/VD = 50.25g / 6.95 cm3= = 7.23 cm3
47 Sample Problem 2. A piece of wood has a density of 0.93 g/ml and a volume of 2.4 ml What is its mass?MM = D x VDVM = 0.93 g/ml x 2.4 ml= = 2.2 g
48 Problem Solving or Dimensional Analysis Identify the unknownWhat is the problem asking forList what is given and the equalities needed to solve the problem.Ex. 1 dozen = 12Plan a solutionEquations and steps to solve(conversion factors)Do the calculationsCheck your work:Estimate; is the answer reasonableUNITSAll measurements need a NUMBER & A UNIT!!
49 Dimensional AnalysisUse the units (__________) to help analyze (______) the problem.Conversion Factors: Ratios of equal measurements.Numerator measurement = Denominator measurementUsing conversion factors does not change the value of the measurementExamples; 1 ft = _____ (_________)1 ft__ or in (_____________ __________)12 in ftdimensionssolve12 inequalityConversionfactors
50 What you are being asked to solve for in the problem will determine which conversion factors need to be used.Common Equalities and their conversion factors:1 lb = _____oz1 mi = ______ft1 yr = ______days1 day = ____hrs1 hr = ____min1 min = ____sec165280365246060
51 Sample Problems using Conversion Factors: How many inches are in 12 miles?Equalities: 1 mi = 5280 ft1 ft = 12 in12miles X X =sig figs = 760,000 inches760,320 inches12 in1 ft5280 ft1 mi
52 2. How many seconds old is a 17 year old? Equalities: 1 yr = 365 days; 1 day = 24 hrs; hr = 60 min; 1 min = 60 sec17 yrs X X X X= 536,112,000 secSig figs = 540,000,000 sec365 day1 yr24 hrs1 day60 min1 hr60 sec1 min
53 3. How many cups of water are in 5.2 lbs of water? Equalities: 1 lb = 16 oz; 8 oz = 1 cup5.2 lbs X X == 10.4 cupsSig figs = 1.0 x 101 cups83.2 cup816 oz1 lb1 cup8 oz
54 Equalities: 1 g = 1000 mg; 1 L = 1000 ml X X = 13.6 g 1 ml 1000 mg 1 g 3. If the density of Mercury (Hg) at 20°C is 13.6 g/ml. What is it’s density in mg/L?Equalities: 1 g = 1000 mg; 1 L = 1000 mlX X =13.6 g1 ml1000 mg1 g1000 ml1 L13,600,000 mg/L13.6 x 107 mg/L