binder1_activity n workshop sb1

8/12/2019 Binder1_Activity n Workshop SB1

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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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1

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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2

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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binder1_activity n workshop sb1

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