INTRODUCTION Matter And Measurement Steps in the Scientific Method 1.Observations - quantitative -...
-
Upload
clara-stewart -
Category
Documents
-
view
216 -
download
0
Transcript of INTRODUCTION Matter And Measurement Steps in the Scientific Method 1.Observations - quantitative -...
INTRODUCTION
Matter And
Measurement
Steps in the Scientific Method
1. Observations
- quantitative
- qualitative
2. Formulating Hypotheses
- possible explanation for the observation
3. Performing Experiments
- gathering new information to decide
whether the hypothesis is valid
Outcomes Over the Long-Term
Theory (Model)
- A set of tested hypotheses that give an
overall explanation of some natural
phenomenon
Natural Law
- The same observation applies to many
different systems
- Example: Law of Conservation of Mass
Law vs. Theory
A law summarizes what happens
A theory (model) is an attempt to explain why
it happens.
Part 1 - Part 1 - number number
Part 2 - Part 2 - scale (unit)scale (unit)
Examples: Examples:
2020 grams grams 6.63 x 106.63 x 10-34-34 Joule secondsJoule seconds
Measurement - quantitative Measurement - quantitative observation observation consisting of 2 partsconsisting of 2 parts
Nature of MeasurementNature of Measurement
(le Système International, SI)(le Système International, SI)
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
The Fundamental SI UnitsThe Fundamental SI Units
SI UnitsSI Units
SI Prefixes Common to Chemistry
Prefix Unit Abbr. Exponent
Mega M 106
Kilo k 103
Deci d 10-1
Centi c 10-2
Milli m 10-3
Micro 10-6
Nano n 10-9
Pico p 10-12
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.
Measurements are performed with instruments No instrument can read to an infinite number of decimal places
AccuracyAccuracy refers to the agreement of a refers to the agreement of a particular value with the particular value with the truetrue (known) (known) value.value.
PrecisionPrecision refers to the degree of agreement refers to the degree of agreement among several measurements made in the among several measurements made in the same manner. (aka – reproducibility)same manner. (aka – reproducibility)
Neither accurate nor
precise
Precise but not accurate
Precise AND accurate
Precision and Accuracy
Types of Error
Random ErrorRandom 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 ErrorSystematic Error (Determinate Error) - (Determinate Error) - Occurs in the Occurs in the same directionsame direction each time each time (high or low), often resulting from poor (high or low), often resulting from poor technique or incorrect calibration. technique or incorrect calibration. This can This can result in measurements that are precise, result in measurements that are precise, but not accurate.but not accurate.
Rules for Counting Significant Figures
1. If the number contains a decimal, count from right to left until only zeros or no digits remain.
Examples: 20.05 grams 4 sig figs 7.2000 meters 5 sig figs 0.0017 grams 2 sig figs
2. If the number does not contain a decimal, count from left to right until only zeros or no digits remain.
Examples: 255 meters 3 sig figs 1,000 kilograms 1 sig fig
3. Exact numbers have an infinite number of significant figures.
1 inch = 2.54 cm, exactly
How many significant figures in each of the following?
1.0070 m
5 sig figs
17.10 kg 4 sig figs
100,890 L 5 sig figs
3.29 x 103 s 3 sig figs
0.0054 cm 2 sig figs
3,200,000 2 sig figs
Sig Fig Practice #1Sig Fig Practice #1
Rules for Significnt Figures in Mathematical
Operations• Addition and SubtractionAddition and Subtraction: The : The
number of decimal places in the number of decimal places in the result equals the number of decimal result equals the number of decimal places in the least precise places in the least precise measurement. measurement.
6.8 + 11.934 = 6.8 + 11.934 =
18.734 18.734 18.7 ( 18.7 (3 sig figs3 sig figs))
Sig Fig Practice #2Sig Fig Practice #2
3.24 m + 7.0 m
Calculation Calculator says: Answer
10.24 m 10.2 m
100.0 g - 23.73 g 76.27 g 76.3 g
0.02 cm + 2.371 cm 2.391 cm 2.39 cm
713.1 L - 3.872 L 709.228 L 709.2 L
1818.2 lb + 3.37 lb 1821.57 lb 1821.6 lb
2.030 mL - 1.870 mL 0.16 mL 0.160 mL
Rules for Significant Figures in Mathematical Operations
• Multiplication and DivisionMultiplication and Division:: # sig # sig figs in the result equals the number figs in the result equals the number in the least precise measurement in the least precise measurement used in the calculation. used in the calculation.
6.38 x 2.0 = 6.38 x 2.0 =
12.76 12.76 13 (2 sig figs)13 (2 sig figs)
Sig Fig Practice #3Sig Fig Practice #3
3.24 m x 7.0 m
Calculation Calculator says: Answer
22.68 m2 23 m2
100.0 g ÷ 23.7 cm3 4.219409283 g/cm3 4.22 g/cm3
0.02 cm x 2.371 cm 0.04742 cm2 0.05 cm2
710 m ÷ 3.0 s 236.6666667 m/s 240 m/s
1818.2 lb x 3.23 ft 5872.786 lb·ft 5870 lb·ft
1.030 g ÷ 2.87 mL 2.9561 g/mL 2.96 g/mL
Converting Celsius to KelvinConverting Celsius to Kelvin
Kelvin = C + 273 °C = Kelvin - 273
Extensive propertiesExtensive properties
Intensive propertiesIntensive properties
Volume
MassEnergy Content (think Calories!)
depend on the amount of matter that is present.
do not depend on the amount of matter present.
Melting point
Boiling point
Density
Properties of MatterProperties of Matter
Three Phases
SolidSolid – definite volume and shape; particles packed in fixed positions.LiquidLiquid – definite volume but indefinite shape; particles close together but not in fixed positionsGasGas – neither definite volume nor definite shape; particles are at great distances from one anotherPlasma – high temperature, ionized phase of matter as found on the sun.
Phase Phase DifferencesDifferences
Classification of Matter
Separation of a MixtureSeparation of a MixtureSeparation of a Mixture
The constituents of the mixture retain The constituents of the mixture retain their identity and may be separated by their identity and may be separated by physical means.physical means.
The components of dyes such as ink may be separated by paper chromatography.
Separation of a MixtureSeparation of a Mixture
The components of dyes such as ink may be separated by paper chromatography.
Separation of a Mixture
Distillation
MatterMatter
Mixtures:a) Homogeneous (Solutions)b) Heterogeneous
Pure SubstancesPure Substances
Compounds ElementsElements
AtomsAtoms
NucleusNucleus ElectronsElectrons
Protons NeutronsNeutrons
QuarksQuarks QuarksQuarks
Organization of MatterOrganization of Matter
Water Hydrogen + Oxygen
H2O H2 + O2
Reactant Products
Compounds must be separated by chemical means.
With the application of electricity, water can be separated into its elements
Separation of a CompoundSeparation of a CompoundThe Electrolysis of water
Dimensional Analysis
- aka: factor label
unit cancellation
fence-post- provides a systematic way of solving
numerical problems
Set-up: Given Desired Units___ 1 Units to Eliminate
Dimensional Analysis Examples
• 115 lbs = ______ g
115 lbs 453.6 g 5.22 x 104 g 1 1 lb
Useful Conversions
• 1 mi = 1.6093 km
• 1 lb = 453.59 g
• 1 in = 2.54 cm
• 0F = (9/5) 0C + 32
• 1 L = 1.0567 qt
• 1 mL = 1cm
• 1 kg = 2.2046 lb
• 0C = (5/9)( 0F – 32 )
3