1 Steps in the Scientific Method 1.Observations quantitative quantitative qualitative qualitative...
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Transcript of 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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5
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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Rules for Counting Significant Figures - Details
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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Rules for Counting Significant Figures - Details
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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Rules for Counting Significant Figures - Details
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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Rules for Counting Significant Figures - Details
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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18
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.