Binder1_Activity n Workshop SB1
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Transcript of Binder1_Activity n Workshop SB1
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8/12/2019 Binder1_Activity n Workshop SB1
1/12
MeasurementinScienceSignificantFiguresandScientificNotationWhy?
All sciences involve observations sometimes qualitative and sometimes quantitative.
Quantitativeobservationsinvolvemeasurementinoneformoranother. Itmaybemeasurementof
adistance,
avolume,
amass
or
any
one
of
arange
of
other
quantitative
data.
How
the
numbers
from a measurement are written is important in science as it gives information about the
instruments used tomake themeasurement hence it important to understand the concepts of
significantfiguresandscientificnotation.
SuccessCriteria Recognisethatthenumberofsignificantfiguresindicatesthelevelofaccuracyoftheinstrument
usedtomakethemeasurement
Identifythenumberofsignificantfiguresinanumber WritenumbersinscientificnotationResources
Textbook(Chapter2)Information
SignificantfiguresThe accuracy of any measurement we make is limited by the instrument we use to make the
measurementor thephysical constraintsof the situation. When recording themeasurementwe
must do so in a way that tells a reader the level of accuracy (or, if you prefer, the degree of
uncertainty)in
the
instrument
used
to
make
the
measurement.
Atthetopoftherulershownbelowthedivisionsareinincrementsofonemillimetre,mm. Thefirst
arrow indicatesapositionbetween2.2and2.3. It is incorrect to record itas2.2mmor2.3mm
becausewe know it is longer than 2.2mm and shorter than 2.3mm. We estimate the second
decimalplacewemightestimatethepositiontobe2.22andwouldrecordthisas2.22mm. This
tellsustherulerhasa levelofaccuracyto2decimalplacesthe lastdigit isuncertainbutweare
certainitislongerthan2.2mmandshorterthan2.3mm. Evenifthepositionweretobeexactlyononeofthemarkswemustrecord2decimalplaces. Forexample, ifthepositionwasexactlyat6(secondarrow)wewouldrecord6.00mmweneedtoincludethezerossoastoinformthereader
that a ruler capable of reading to 2 decimal places was used. The numbers we record in a
measurementare
described
as
significant figures they are significant because they give
informationaboutthelevelofaccuracyofthetoolusedtomakethemeasurement.
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ScientificnotationTheverylargeorverysmallnumbersoftenusedinthesciencescanbedifficulttowriteinstandard
decimal notation. To overcome this problem numbers are frequently written using scientific
notation. Scientificnotationisbasedonpowersofthebasenumber10withnumberswritteninthe
followinggeneralform:
a 10b
whereaisrealnumberbetween0and10.
Forexamplethespeedoflightwhichis300000000ms1
(threehundredmillionmetrespersecond)
ismoreconvenientlywrittenas
3108ms
1
Thenumber0.0000456writteninscientificnotationis4.56105.
Thepowerof10(thevalueofbinthegeneralform)givesthenumberofplacesthedecimalpointis
movedand
in
which
direction.
If
the
decimal
point
is
moved
to
the
left
b
is
positive;
movement
to
therightmeansbisnegative.
Table1: Scientificnotationfornumbersincreasingbyfactorsof10from0.000001to100000.
Number Scientificnotation Number Scientificnotation0.000001 1x10
61 1x10
0
0.00001 1x105
10 1x101
0.0001
1x10
4
100
1x10
2
0.001 1x103
1000 1x103
0.01 1x102
10000 1x104
0.1 1x101
100000 1x105
SignificantfiguresincalculationsUseChapter2ofyourtext(pp.2529)tounderstandhowtousesignificantfiguresincalculations.
KeyQuestionsEndofchapter2QuestionsandProblems4,6,8,10,30,32,40,46,48,50
Thefollowingwebsitecanalsoprovidepracticewithscientificnotation.
http://janus.astro.umd.edu/astro/scinote/
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ChemicalandPhysicalPropertiesandChangesandClassificationofMatterWhy?
Tounderstand theway inwhichmatterbehaves, it isuseful tobeable to recognisehowmatterisorganisedandthetypesofchangesitmayundergo.SuccessCriteria Identifychemicalandphysicalchanges. Recognise that physically matter can be classified into homogenous substances andheterogeneoussubstances
Identifyhomogenoussubstancesandheterogeneoussubstances Recognisethatchemicallymattercanbeclassifiedintopuresubstancesandmixtures Recognisethatpuresubstancescanbeclassifiedintoelementsandcompounds Defineanelementasasubstancecontainingonlyonetypeofatom Defineacompoundasasubstancecontaining2ormoretypesofatomsResources Textbook(Chapter3)InformationPhysicalandChemicalChangesChemistry can be described as the study ofmatter, its properties and its transformations. Allsubstances (matter)havephysicalandchemicalpropertiesandcanundergophysicalandchemicalchanges.Typicalphysicalproperties include colour,density, volume, state (solid, liquidor gas). When thephysicalpropertiesof a substance change, the chemical composition of that substance doesnotchangethereisnonewsubstanceformed.Often physical changes involve a change in state. Changes in state are usually associatedwithchangesintemperature.
Chemical properties refer to a substances capacity to form new substances. During chemicalchangenewsubstancesareformedandothersareconsumed.Examples:
Dissolvinglimestonewithanacid Rustingofiron Combustionofgas
SOLID
LIQUID GAS
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KeyQuestions1. Identifywhichofthefollowingarephysicalchangesandwhicharechemicalchanges.a. Digestingfoodb. Cookinganeggc. Boilingalcohold. Bleachinghairwithperoxidee. Cuttinganappleintopieces.
2. Givetwofurtherexamplesofa. physicalchanges
b. chemicalchanges
ElementsandCompoundsMuchof thematterweencounter ineveryday life isnotpure it isamixture. Mixturescanbeseparatedintopuresubstances.
Compoundscanbebrokendownintosimplersubstancesbychemicalprocesses. Eventually,aswecontinue to break down a substancewe reach a pointwhere it cannot be broken down in to achemicallysimplersubstance. Atthisstagewehaveanelement.Elementscannotbedecomposedintochemicallysimplersubstances.Compoundsaremadeof2ormoreelementschemicallycombined.
Physicalprocesses
MIXTURES PURESUBSTANCES
(elements/compounds)
Canbeseparated Cannotbefurtherseparated(byphysicalprocesses)
distillationfiltrationdecantationetc
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Model1: AWayofClassifyingMatter
Newsubstanceformed. i.e.compositionchanges
Puresubstancesarealsohomogeneous
PURITY
PHYSICAL
CHANGES
CHEMICALPhysicalformchangeswithoutchangeincomposition.
Mixture(impuresubstance;variablecomposition)
HomogeneouspropertiesareconstantthroughoutEg.
Salt
water,
air,
brass
Heterogeneousvariablepropertiesthroughout
MATTER
Compoundcontains2ormoretypesofatoms. Canbeseparatedbychemicalmeansintoitselements.Eg.Water,H2O
Elementcontainsonlyonetypeofatom. Cantbefurtherseparated.
Puresubstances(fixedcomposition;propertiesdontchangeonfurtherpurification)
(reactions)
Chemicalprocesses
COMPOUNDS ELEMENTS
Canbedecomposed(brokendown) Cannotbedecomposed(brokendown)
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Someexamplesoftheclassificationofmatterare: Oxygengasat25Cpuresubstance,element,homogeneous Sugardissolvedinwaterat25Cmixture,homogeneous Waterat0Cpuresubstance,compound(H2O),homogeneous(assumingnoicepresent),heterogeneous(withicepresent)
Teawithtealeavespresentmixture,heterogeneousKeyQuestions1. Identifythefollowingasapuresubstance,ahomogeneousmixtureoraheterogeneousmixture.a. Instantcoffeedissolvedinhotwaterb. Acarbonateddrinkwiththelidscrewedonc. Acarbonateddrinkwiththelidremovedd. Smokeyaire. Sugarf. Mountainairg. Nitrogengasinagascylinder
2.Whichofthefollowingstatementsaboutelementsandcompoundsistrue?a. Mostelementsarefoundfree(i.e.intheirpurestate)innature.b. Compoundsarepuresubstances.c. Compoundscanbeseparatedintotheirconstituentelementsbyphysicalprocesses.d. Elementshavevariableproperties.e. Compoundshaveuniformproperties.f. Asampleofacompoundinoneplacewillhavethesamecompositionasasampleofthesamecompoundinadifferentplace.
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Pure Substance
Mixture bc there are >1 substance present dissolved - homogeneous
Mixture - Hetrogeneous
Pure Substance - compound
All pure substances are homogeneous
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Physical - H2O(s) ---> H2O(l)
Chemical
Physical
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Compounds
Element - Molecule
Compounds
Compounds
Element - Molecule
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