1 steps in the scientific method 1.observations quantitative quantitative qualitative qualitative...

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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

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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 overall explanation of some

natural natural phenomenon.phenomenon.

Natural LawNatural Law

The same observation applies to manyThe same observation applies to many different systemsdifferent systems

Example - Law of Conservation of Example - Law of Conservation of MassMass


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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.


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Nature of Measurement

Measurement - quantitative observation consisting of Measurement - quantitative observation consisting of 2 parts2 parts

Part 1 - numberPart 1 - number Part 2 - scale (unit)Part 2 - scale (unit)

Examples:Examples:20 grams20 grams

6.63 6.63 Joule seconds Joule seconds


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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.


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The Fundamental SI Units


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Uncertainty in Measurement

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


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Precision and Accuracy

Accuracy Accuracy refers to the agreement of a refers to the agreement of a particular value with theparticular value with the true true value.value.

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


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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 directionsame direction each time (high each time (high or low), often resulting from poor technique.or low), often resulting from poor technique.


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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


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Rules for Counting Significant Figures - Details

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

3456 3456 has has

4 4 sig figs.sig figs.


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ZerosZerosLeading zerosLeading zeros do not count as do not count as

significant figures.significant figures.

0.04860.0486 has has

33 sig figs. sig figs.


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ZerosZeros Captive zerosCaptive zeros always count as always count as

significant figures.significant figures.

16.07 16.07 hashas

4 4 sig figs.sig figs.


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ZerosZeros Trailing zerosTrailing zeros are significant only are significant only

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

9.3009.300 has has

44 sig figs. sig figs.


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

11 inch = inch = 2.54 2.54 cm, exactlycm, exactly


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Rules for Significant Figures in Mathematical Operations

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

6.38 6.38 2.0 = 2.0 =

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


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Rules for Significant Figures in Mathematical Operations

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

6.8 + 11.934 =6.8 + 11.934 =

22.4896 22.4896 22.5 (3 sig figs)22.5 (3 sig figs)


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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.


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Temperature

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

Fahrenheit scale =Fahrenheit scale =FF


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Temperature


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Density

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

volume of the substance:volume of the substance:


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Matter:Matter: Anything occupying Anything occupying

space and having mass.space and having mass.


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Classification of Matter

Three States of Matter:Three States of Matter:

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

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

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


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Types of Mixtures

Mixtures have variable composition.Mixtures have variable composition.

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

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


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Pure Substances

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

ChromatographyChromatography

FiltrationFiltration

DistillationDistillation


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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.

1 steps in the scientific method 1.observations quantitative quantitative qualitative qualitative...

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conservation of mass

significant figures

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