Measurements and Measurements and CalculationsCalculations

Chapter 2Chapter 2

Honors ChemistryHonors Chemistry

GarciaGarcia

2-1 Objectives2-1 Objectives

Describe the purpose of the scientific Describe the purpose of the scientific method.method.

Distinguish between qualitative and Distinguish between qualitative and quantitative observations.quantitative observations.

Describe the differences between Describe the differences between hypotheses, theories, and models.hypotheses, theories, and models.

Scientific MethodScientific Method

logical approach to:logical approach to: solving problems by observing & solving problems by observing &

collecting datacollecting data formulating hypothesesformulating hypotheses testing hypothesestesting hypotheses formulating theories that are formulating theories that are

supported by datasupported by data

Quantitative vs. QualitativeQuantitative vs. Qualitative

quantitative measurement- numerical quantitative measurement- numerical informationinformation

qualitative measurement- descriptive, qualitative measurement- descriptive, non-numerical informationnon-numerical information

system- specific portion of matter in a system- specific portion of matter in a given region of space that is being given region of space that is being studiedstudied

Scientific MethodScientific Method

hypothesis- educated guess; testable hypothesis- educated guess; testable statementstatement

model- explanation of how things model- explanation of how things occur and how data/events are occur and how data/events are relatedrelated

theory- broad generalization that theory- broad generalization that explains a body of factsexplains a body of facts

2-2 Objectives2-2 Objectives

Distinguish between a quantity, a unit, Distinguish between a quantity, a unit, and a measurement standard.and a measurement standard.

Name SI units for length, mass, time, Name SI units for length, mass, time, volume, and density.volume, and density.

Distinguish between mass and weight.Distinguish between mass and weight. Perform density calculations.Perform density calculations. Transform a statement of equality to a Transform a statement of equality to a

conversion factory.conversion factory.

Le System International d’UnitesLe System International d’Unites

SI system- International System of Units SI system- International System of Units adopted in 1960adopted in 1960

Seven base units:Seven base units: lengthlength massmass time time temperaturetemperature amount of a substanceamount of a substance electric currentelectric current luminous intensityluminous intensity

QuantityQuantity SymbolSymbol Unit Unit NameName

Unit Unit AbbreviatioAbbreviationn

lengthlength ll metermeter mm

massmass mm kilogramkilogram kgkg

timetime tt secondsecond ss

temperaturetemperature TT kelvin kelvin KK

amount of a amount of a substancesubstance

nn molemole molmol

electric electric currentcurrent

II ampereampere AA

luminous luminous intensityintensity

IIVV candelacandela cdcd

prefiprefixx

unit unit abbreviationabbreviation

exponentiexponential factoral factor

meaningmeaning

teratera TT 10101212 1 trillion1 trillion

gigagiga GG 101099 1 billion1 billion

megamega MM 101066 1 million1 million

kilokilo kk 101033 10001000

hectohecto hh 101022 100100

dekadeka dada 101011 1010

prefixprefix unit unit abbreviatioabbreviationn

exponentiexponential factoral factor

meaningmeaning

decideci dd 1010-1-1 1/101/10

centicenti cc 1010-2-2 1/1001/100

millimilli mm 1010-3-3 1/10001/1000

micromicro 1010-6-6 1/10000001/1000000

nanonano nn 1010-9-9 1/10000000001/1000000000

picopico pp 1010-12-12 1/10000000000001/1000000000000

femtofemto ff 1010-15-15 1/10000000000000001/1000000000000000

atto atto aa 1010-18-18 1/10000000000000001/1000000000000000000000

Units of MeasurementUnits of Measurementderived units- a combination of SI base unitsderived units- a combination of SI base units

quantityquantity symbosymboll

unitunit abbreviatioabbreviationn

derivationderivation

areaarea AA square square metermeter

mm22 length x widthlength x width

volumevolume VV cubic metercubic meter mm33 length x width x heightlength x width x height

densitydensity DD kilograms kilograms per cubic per cubic metermeter

kg/mkg/m33 mass/volumemass/volume

molar massmolar mass MM kilograms kilograms per moleper mole

kg/molkg/mol mass/amount of mass/amount of substancesubstance

concentraticoncentrationon

cc moles per moles per literliter

MM amount of amount of substance/volumesubstance/volume

molar molar volumevolume

VVmm cubic cubic meters per meters per molemole

mm33/mol/mol volume /amount of volume /amount of substancesubstance

energyenergy EE joule joule JJ force x lengthforce x length

Units of MeasurementUnits of Measurement

volume- amount of space occupied by volume- amount of space occupied by an object an object

1 cm1 cm33 = 1 mL = 1 mL

density- ratio of mass to volumedensity- ratio of mass to volume

D = m/vD = m/v

What is the density of a block of What is the density of a block of marble that occupies 310 cmmarble that occupies 310 cm33 and and has a mass of 853 g?has a mass of 853 g?

Diamond has a density of 3.26 g/cmDiamond has a density of 3.26 g/cm33. . What is the mass of a diamond that What is the mass of a diamond that has a volume of 0.350 cmhas a volume of 0.350 cm33??

Conversion FactorsConversion Factors

conversion factor- ratio derived from conversion factor- ratio derived from the equality between two different the equality between two different unitsunits

ex. seconds to hoursex. seconds to hours

feet to inchesfeet to inches

You have a chili recipe that serves ten. You have a chili recipe that serves ten. The recipe calls for two teaspoons of The recipe calls for two teaspoons of chili powder. How much chili powder chili powder. How much chili powder do you need for 600 servings?do you need for 600 servings?

How many seconds are there in one How many seconds are there in one day? day?

Express 750 dg in grams.Express 750 dg in grams.

Convert 0.107 g to kilograms. Convert 0.107 g to kilograms.

What is 0.073 cm in micrometers? What is 0.073 cm in micrometers?

2-3 Objectives2-3 Objectives

Distinguish between accuracy and Distinguish between accuracy and precision.precision.

Determine the number of significant Determine the number of significant figures in measurements.figures in measurements.

Perform mathematical operations Perform mathematical operations involving significant figure.involving significant figure.

Convert measurements into scientific Convert measurements into scientific notation.notation.

Distinguish between inversely and directly Distinguish between inversely and directly proportional relationships.proportional relationships.

Accuracy vs. PrecisionAccuracy vs. Precision

accuracy- closeness of measurements accuracy- closeness of measurements to the correct or accepted valueto the correct or accepted value

precision- closeness of a set of precision- closeness of a set of measurements of the same quantity measurements of the same quantity made in the same waymade in the same way

Percent ErrorPercent Error

accepted value – experimental valueaccepted value – experimental value x x 100100

accepted valueaccepted value

What is the percent error for a mass What is the percent error for a mass measurement of 17.7 g, given that measurement of 17.7 g, given that the correct value is 21.2 g?the correct value is 21.2 g?

A volume is measured experimentally A volume is measured experimentally as 4.26 mL. What is the percent as 4.26 mL. What is the percent error, given that the correct value is error, given that the correct value is 4.15 mL? 4.15 mL?

Significant FiguresSignificant Figures

measurement of all known digits with measurement of all known digits with certainty plus one estimated digitcertainty plus one estimated digit

1. zeros between nonzero digits are 1. zeros between nonzero digits are significantsignificant

32013201 101101 5000250002

2. zeros appearing before nonzero 2. zeros appearing before nonzero digits are digits are notnot significant significant

0.00430.0043 0.3580.358 0.03020.0302

Significant FiguresSignificant Figures

3. zeros at the end of a number & to the 3. zeros at the end of a number & to the right of a decimal point are significantright of a decimal point are significant

62.062.0 3.00003.0000 29.00000029.000000

4. zeros at the end of a number but the 4. zeros at the end of a number but the left of a decimal may or may not be left of a decimal may or may not be significant; a decimal point placed after significant; a decimal point placed after the zeros indicate they are significantthe zeros indicate they are significant

45004500 4500.4500. 3200000.3200000.