Chapter 1 Introduction: Matter and Measurement. Steps in the Scientific Method 1.Observations -...

Chapter 1

Introduction: Matter and Measurement

Steps in the Scientific Method

1.1. ObservationsObservations

--quantitativequantitative

--qualitativequalitative

2.2. Formulating hypothesesFormulating hypotheses

-- possible explanation for the observationpossible explanation for the observation

3.3. Performing experimentsPerforming experiments

-- gathering new information to decidegathering new information to decide

whether the hypothesis is validwhether the hypothesis is valid

Outcomes Over the Long-Term

Theory (Model)Theory (Model)--A set of tested hypotheses that give anA set of tested hypotheses that give an overall explanation of some natural overall explanation of some natural

phenomenon.phenomenon.

Natural LawNatural Law-- The same observation applies to many The same observation applies to many different systemsdifferent systems

-- Example - Law of Conservation of MassExample - Law of Conservation of Mass

The Scientific Method

01_03

Observation

Hypothesis

Experiment

Theory(model)

Experiment

Theorymodifiedas needed

Prediction

Law

Law v. Theory

A A lawlaw summarizes what happens; summarizes what happens;a a theorytheory (model) is an attempt to (model) is an attempt to explain explain whywhy it happens. it happens.

Nature of Measurement

Measurement - quantitative observation consisting of 2 partsMeasurement - quantitative observation consisting of 2 parts

Part 1 - Part 1 - numbernumberPart 2 - Part 2 - scale (unit)scale (unit)

Examples:Examples:2020 gramsgrams

6.63 6.63 Joule secondsJoule seconds

International System(le Système International)

Based on metric system and units Based on metric system and units derived from metric system.derived from metric system.

The Fundamental SI Units

Physical Quantity Name Abbreviation

Mass kilogram kg

Length meter m

Time second s

Temperature Kelvin K

Electric Current Ampere A

Amount of Substance mole mol

Luminous Intensity candela cd

Uncertainty in Measurement

A digit that must be A digit that must be estimatedestimated is is called called uncertainuncertain. A . A measurementmeasurement always has some degree of always has some degree of uncertainty.uncertainty.

01_08

0

10

20

30

40

50

mL

Buret

22.2 mL

Precision and Accuracy

AccuracyAccuracy refers to the agreement of a refers to the agreement of a particular value with the particular value with the true true value.value.

PrecisionPrecision refers to the degree of refers to the degree of agreement among several elements of agreement among several elements of the same quantity.the same quantity.

Figure 01.24a

Figure 01.24ab

Figure 01.24

Types of Error

Random Error Random Error (Indeterminate Error) - (Indeterminate Error) - measurement has an equal probability of measurement has an equal probability of being high or low.being high or low.

Systematic Error Systematic Error (Determinate Error) - (Determinate Error) - Occurs in the Occurs in the same direction same direction each time each time (high or low), often resulting from poor (high or low), often resulting from poor technique.technique.

Rules for Counting Significant Figures - Overview

1.1. Nonzero integersNonzero integers

2.2. ZerosZeros

-- leading zerosleading zeros

-- captive zeroscaptive zeros

-- trailing zerostrailing zeros

3.3. Exact numbersExact numbers

Rules for Counting Significant Figures - Details

Nonzero integers Nonzero integers always count as always count as significant figures.significant figures.

34563456 has has

44 sig figs. sig figs.

Rules for Counting Significant Figures - Details

ZerosZeros--Leading zerosLeading zeros do not count as do not count as

significant figures.significant figures.

0.04860.0486 has has

33 sig figs. sig figs.

Rules for Counting Significant Figures - Details

ZerosZeros-- Captive zeros Captive zeros always count asalways count as

significant figures.significant figures.

16.07 16.07 hashas

44 sig figs. sig figs.

Rules for Counting Significant Figures - Details

ZerosZeros-- Trailing zerosTrailing zeros are significant are significant

onlyonly if the number contains a if the number contains a decimal point.decimal point.

9.3009.300 has has44 sig figs. sig figs.

Rules for Counting Significant Figures - Details

Exact numbersExact numbers have an infinite number have an infinite number of significant figures.of significant figures.

11 inch = inch = 2.542.54 cm, exactlycm, exactly

Rules for Significant Figures in Mathematical Operations

Multiplication and Division:Multiplication and Division: # sig figs # sig figs in the result equals the number in the in the result equals the number in the least precise measurement used in the least precise measurement used in the calculation.calculation.

6.38 6.38 2.0 = 2.0 =

12.76 12.76 13 (2 sig figs)13 (2 sig figs)

Rules for Significant Figures in Mathematical Operations

Addition and Subtraction:Addition and Subtraction: # decimal # decimal places in the result equals the number of places in the result equals the number of decimal places in the least precise decimal places in the least precise measurement.measurement.

6.8 + 11.934 =6.8 + 11.934 =

18.734 18.734 18.7 (3 sig figs)18.7 (3 sig figs)

Dimensional Analysis

Proper use of “unit factors” leads to proper Proper use of “unit factors” leads to proper units in your answer.units in your answer.

1 in = 2.54 cm

1 pound = 453.59 g

1 gallon = 3.7854 L

Figure 01.25-02UNEOC

Figure 01.25-03UN

Dimensional Analysis

1.49 (b) The recommended adult dose of Elixophyllin®, a drug used to treat asthma, is 6 mg/kg of body mass. Calculate the dose in milligrams for a 150-lb person. (1 lb=453.59 g)

Temperature

Celsius scale =Celsius scale =CCKelvin scale = KKelvin scale = K

Fahrenheit scale =Fahrenheit scale =FF

Temperature

T T

T TF

5 C

K C

F C

27315

932

.

F

Figure 01.17

Density

DensityDensity is the mass of substance per unitis the mass of substance per unit

volume of the substance:volume of the substance:

density = mass

volume

Table 01.06

Using Density

Determine the thickness of a sheet of platinum, in millimeters, that is a square 1.25 in. per side. The piece of platinum weighs 1.656 grams. (The density of Pt is 21.45 g cm-3)

Matter:Matter: Anything Anything occupying space and occupying space and

having mass.having mass.

The Big Bang

Classification of Matter

Three States of Matter:Three States of Matter:

Solid: Solid: rigid - fixed volume and shaperigid - fixed volume and shape

Liquid: Liquid: definite volume but assumes the definite volume but assumes the shape of its containershape of its container

Gas: Gas: no fixed volume or shape - assumes no fixed volume or shape - assumes the shape of its containerthe shape of its container

Figure 01.04

Types of Mixtures

Mixtures have variable composition.Mixtures have variable composition.

AA homogeneous mixture homogeneous mixture is a solution is a solution (for example, vinegar)(for example, vinegar)

AA heterogeneous mixture heterogeneous mixture is, to the is, to the naked eye, clearly not uniform (for naked eye, clearly not uniform (for example, a bottle of ranch dressing)example, a bottle of ranch dressing)

Mixtures and Compounds

Pure Substances

Can be isolated by separation methods:Can be isolated by separation methods:

-- ChromatographyChromatography

-- FiltrationFiltration

-- DistillationDistillation

Figure 01.14

Figure 01.12

Electrolysis of Water

Figure 01.07

Compound or Element

Element:Element: A substance that cannot be A substance that cannot be decomposed into simpler substances by decomposed into simpler substances by chemical means.chemical means.

Compound:Compound: A substance with a A substance with a constant composition that can be constant composition that can be broken down into elements by broken down into elements by chemical processes.chemical processes.

01_15

Heterogeneousmixtures

Physicalmethods Homogeneous

mixtures (solutions)

Atoms

Compounds Elements

Nucleus Electrons

Pure substances

Protons Neutrons

Quarks Quarks

Matter

Physicalmethods

Chemicalmethods

Elemental Composition

End