Matter and Measurements Honors Chemistry IA - PowerPoint Presentation

Slide1

Matter and Measurements

Honors Chemistry IA

Unit 1Slide2

Atoms are the submicroscopic particles that make up the basic building blocks of matter

“Smallest unit of matter”

These come together to form molecules (covalent) and compounds (ionic)

Atoms and Molecules Slide3

One carbon

atom

for each oxygen atommake up the moleculecarbon monoxide

Two hydrogen atoms for each oxygen atom

make up waterSlide4

Studying these atoms and how they arrange is of interest to chemists

“Chemistry” – the science that seeks to understand the behavior of matter by studying the behavior of atoms and molecules

Focusses on matter and the changes they undergoEnergy and matter conservationChemistry Slide5

Scientists observe and perform experiments on the physical world to learn about it

The Scientific Method is a series of steps used to organize and test hypotheses, collect data, and formulate conclusions

The Scientific MethodSlide6

Observations often lead scientists to formulate a

hypothesis

Hypothesis is an interpretation or explanation of an observationMUST be written in “if/then” form and MUST BE TESTABLE!!!!We then test, or experiment, these hypotheses to verify if we are correct or if we need to go back  Slide7

Some conclusions may be a Scientific Law or a Theory.

What is the difference ??

A Law summarizes past observations and predicts future ones. i.e. the Law of Conservation of MassA theory a proposed explanation for observations based on well-established and tested hypotheses.Slide8

Collecting observations is a critical part throughout each step

You observe to hypothesize

Experiment and then observeObserve and then analyzeObserve and then form a conclusionThe Scientific MethodSlide9

You go out in the morning before school in D

ecember and your car wont start. Use the scientific method to figure out a possible solution.

PracticeSlide10

Matter is anything that has mass and takes up space… in other words: anything with mass and volume

Matter can exist in three states (or phases)

Solid – atoms are tightly packed together Liquid – not as tight; able to slide past one anotherGas – very loose; bouncing all over; no definite shape or volume compressible Classification of MatterSlide11
Slide12

Solid matter may also exhibit a crystalline structure.

This is a long-range, repeating order such as diamond

Very STRONG and STABLESolids Slide13

Liquids are not compressible and are packed nearly as tightly as solids

They are able to move freely past one another in a fluid motion

This enables them to be “poured” and explains the large range of motion of these particlesLiquidsSlide14

Atoms have A LOT of space between molecules / atoms

They are free to move in three dimensions past and around one another

They are COMPRESSIBLE!!GasesSlide15
Slide16

Classifying MatterSlide17

If you are a pure substance, you can either be a pure elemental or a pure compound

Elemental – consisting of only one type of atom

Compound – composed of two or more elements (such as water and carbon dioxide)Pure SubstancesSlide18

Heterogeneous Mixtures:

Composition varies throughout

If you sample from one spot it may not be the same as a sample from anotherSalad, Pizza, ...Homogeneous Mixtures:Same composition throughout; uniformKool-Aid, Salt water, ...MixturesSlide19

Separation techniques target

physical properties

to isolate and separate the components back outCan be very easy or a little more elaborateSeparating MixturesSlide20
Slide21

Changes that alter only the state or the appearance but do not change the chemical composition are

physical changes

A Physical Property is one that a substance displays without changing its compositionPhysical Changes and PropertiesSlide22
Slide23

A

Chemical Change

is a change that alters the composition or matterDuring a chemical change, atoms rearrange and transform a starting substance into a new substance “Bonds are broken, reformed, and gives you something new”A chemical property is one that a substance displays only by changing its composition via a chemical changeChemical Properties and ChangesSlide24

Chemical PropertiesSlide25

Determine whether each of the following changes is physical or chemical

The evaporation of rubbing alcohol

The burning of lamp oilThe bleaching of hair with hydrogen peroxideThe forming of frost on a cold nightA copper wire hammered flatA nickel dissolves in acid to form a blue-green solutionDry ice vaporizes without meltingA match ignites when struck on a flintPracticeSlide26

Energy exchange is necessary for a chemical or physical change to take place

What is energy??

Energy is the “capacity to do work” What are two types of energy?? Kinetic and Potential

Energy Slide27

Kinetic Energy is the total energy associated with its motion (energy from motion)

Potential is energy from rest… “it has potential – though not moving yet”

Kinetic vs. PotentialSlide28

Thermal Energy

is the energy associated with the temperature of an object

It may got hot or cold… both exhibit a change in temperaturesExothermic and Endothermic (review from bio IB)Thermal EnergySlide29

The energy (and mass) put into a system MUST be recovered back out of the system in some way shape or form

“Energy (and mass) is neither created or destroyed”

The Law of Conservation of Energy (and Mass)Principle or Energy #1Slide30

Systems with high potential energy will always have the tendency to change in a way that lowers their potential energy

It “dissipates” out and is absorbed by surrounding bodies or the atmosphere

Principle or Energy #2Slide31

In chemistry UNITS are critical

Units

– the standard quantities used to specify measurements Gives a number meaning, without units they are nothingWe also need units that AGREE with one another regardless of who or where in the world we are workingUnits of MeasurementSlide32

Two main types of measurement:

English System

(The American System) – used in the U.S.The Metric System – used in most other parts of the world Scientists all around the world use the Metric System a.k.a. the International System of Units (SI)Units of MeasurementSlide33

SI Units: Standard UnitsSlide34

Temperature ScalesSlide35

Scientists use Celsius or Kelvin when measuring temperature

There is nothing “Easy” or “clean” about the Fahrenheit Scale (not SI units)

When given anything in F, you must first convert to C or KWhat Units do we want??Slide36

Convert:

212

℃  ?? ℉ 47 ℉  ?? ℃185 ℃  ?? ℉ 275 ℃  ?? ℉

76 ℉  ?? ℃ 123 ℃  ??

-22

℉

 ?? ℃ -17.1 ℃  ?? K

4 ℉  ?? KSlide37

The Metric System (SI) is a “base 10” scale

Meaning, conversions are as simple as moving the decimal over

Prefixes are used as multipliers to denote valuesEx: kilo- means 103 milli- means 10-3 (1,000) (0.001)Metrics Made EasySlide38
Slide39
Slide40

Derived units can be made by combining other units together.

Usually, these units are a measurement “per” another (such as meters “per” second, or grams “per” mole)

These units will tell you the mathematical derivation of the value Derived UnitsSlide41

Density is defined as the amount of mass in a given space (the mass “per” volume)

The unit to represent this is g/mL or g/cm

3As the unit indicates, the mathematical equation for density is:

Density: A derived unitSlide42

Density is an example of an

intensive property

A property that is independent of the amount of the substance Mass, in contrast, is an example of an extensive propertyA property that is dependent (or depends on) the amount of the substanceSlide43

Calculate the density of a sample with a mass of 4.53 grams and a volume of 0.212 mL (0.212 cm

3

)A metal cube has an edge length of 11.4 mm and a mass of 6.67 g. Calculate the density of the metal  use your table on page 20 to determine the identity of this unknown.Practice with CalculationsSlide44

A man receives a platinum ring from his fiancé

. Before the wedding, he notices that the ring feels a little light for its size and decides to measure its density. He places the ring on a balance and finds that it has a mass of 3.15 grams. He then find that the ring displaces 0.233 cm

3 of water. Is the ting made of platinum (Pt)? Or is it a fake???Slide45

Which data set seems to be more certain and reliable?

Reliability and

SigFigsYear

Carbon Monoxide

Concentration (ppm)

Year

Carbon Monoxide Concentration (ppm)

199715.0199715

199811.5199812

1999

11.1

1999

11

2000

9.9

2000

10

2001

7.2

2001

7

2002

6.5

2002

7Slide46

Scientific measurements are reported so that every digit is certain except the last, which is always estimated!!

So, that means you measure out as far as you know for sure!! And

thennnn estimate one more digit. If it right between two lines you may estimate it to be 0.5 and so on… the last one is not incorrect but an estimateSlide47

Read each to the correct number of

SigFigsSlide48

The non-place-holding digits (those that are not simply marking the decimal place) are called

significant digits

or significant figuresThe greater the number of significant figures, the greater the certainty of the measurement 23.45 certain23.5 less certain24 least certainCounting SigFigsSlide49

All nonzero numbers are significant (1, 2, ..)

Sandwiched zeroes are significant (between two nonzero numbers) (8,008 & 9,000,001)

Leading zeroes (to the left of a nonzero) are not significant (0.00323 & 0.00006)Trailing zeroes after a decimal point are always significant (12.00 & 1.000x104)Trailing zeroes with no decimal are not significant (1200 & 145,000) careful

tho… 1200. makes them significant

RulesSlide50

Exact numbers are always significant, regardless of zeroes

Counted

values, conversion factors, constants are exact“I have 600 skittles in my pocket… not 597 rounded up… this is an exact counted numberCalculators DO NOT present values in the proper number of sigfigs!Exact Values have unlimited sigfigs

ExceptionsSlide51

How many

sigfigs

do the following values have? 46.3 lbs 40.7 in. 580 mi 87,009 km 0.009587 m 580. cm

0.0009 kg 85.00 L 580.0 cm 9.070000 cm

400

. L 580.000

cmPracticeSlide52

Multiplying /

Dividing

The answer cannot have more sigfigs than the value with the smallest number of original sigfigs ex: 12.548 x 1.28 = 16.06144

Calculating with

SigFigs

This value only has 3

sigfis

, therefore the final answer must ONLY have 3 sigfigs!Slide53

Multiplying / Dividing

The answer cannot have more

sigfigs than the value with the smallest number of original sigfigs ex: 12.548 x 1.28 = 16.06144 =16.1

Calculating with SigFigs

This value only has 3

sigfis

, therefore the final answer must ONLY have 3

sigfigs!Slide54

How many

sigfigs

with the following FINAL answers have? Do not calculate.12.85 * 0.00125 4,005 * 400048.12 / 11.2 4000. / 4000.0PracticeSlide55

Adding / Subtracting

The result can be NO MORE certain than the least certain number in the calculation (total number)

ex: 12.4 18.387 + 254.0248

284.8118

Calculating with SigFigs

The least certain number is only certain to the “tenths” place. Therefore, the final answer can only go out one past the decimal.Line up the decimal points FIRST, then round and chop offSlide56

ex:

12.4

18.387 + 254.0248

284.8118 =284.7

Calculating with

SigFigs

Least certain number (total number)Slide57

Both addition / subtraction and multiplication / division

Round using the rules after each operation.

Ex: (12.8 + 10.148) * 2.2 = 22.9 * 2.2 = 50.38 = 50.Calculating with SigFigsSlide58

Scientific Notation – a number written a the product of two values:

A number out front

& A x10 to a powerThis notation allows us to easily work with very, very large numbers or very, very small numbers.

Scientific NotationSlide59

The number out front MUST be written with ONLY one value prior to the decimal point

Examples:

a. 3.24x104g= 32,400 grams

b. 2.5x107

mL =

250,000,000 mL

Scientific NotationSlide60

The exponent (x10

4

) value can have a power that is positive or negative, depending on if you are dealing with a SMALL number or a LARGE numberExamples: a. 8.55x104g b. 4.67x10-4

L = 85,500 grams = 0.000467

Liters

Scientific NotationSlide61

Addition / Subtraction

6.2 x 10

4 + 7.2 x 103 Scientific NotationSlide62

Addition / Subtraction

6.2 x 10

4 + 7.2 x 103 First, make exponents the same62 x 103 + 7.2 x 103

Do the math and put back in Scientific Notation

Scientific NotationSlide63

Multiplication / Division

3.1 x 10

3 * 5.01 x 104 The “mantissas” are multiplied and the exponents are added.(3.1 * 5.01) x 103+416 x 107 = 1.6 x 108

Do the math and put back in Scientific Notation (with correct number of sigfigs)

Scientific NotationSlide64

Accuracy Vs. Precision

Measuring and obtaining data experimentally always comes with some degree of error.

Human or method errors & limits of the instrumentsWe want BOTH accuracy AND precisionSlide65

Selecting the right piece of equipment is key

Beaker, Graduated Cylinder,

Buret?Measuring 1.5 grams with a balance that only reads to the nearest whole gram would introduce a very large error.Experimental ErrorSlide66

So what is Accuracy?

Accuracy of a measurement is how close the measurement is to the TRUE value

“bull’s-eye”AccuracySlide67

An experiment calls for 36.4 mL to be added

Trial 1: delivers 36.1 mL

Trial 2: delivers 36.6 mLWhich is more accurate???Trial 2 is closer to the actual value (bull’s-eye), therefore it is more accurate that the first deliveryAccuracySlide68

Now, what about Precision??

Precision is the exactness of a measurement.

It refers to how closely several measurements of the same quantity made in the same way agree with one another.“grouping”PrecisionSlide69
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Maximizing

Accuracy and Precision will help to

Minimize ERRORError is a measure of all possible “mistakes” or imperfections in our lab dataAs we discussed, they can be caused from us (human error), faulty instruments (instrumental error), or from simply selecting the wrong piece of equipment (methodical error)ErrorSlide71

Error can be calculated using an “Accepted Value” and comparing it to the “Experimental Value”

The

Accepted Value is the correct value based on reliable resources (research, textbooks, peers, internet)The Experimental Value is the value YOU measure in lab. It is not always going to match the Accepted value… Why not??

ErrorSlide72

Error is measured as a percent, just as your grades on a test.

Percent Error =

accepted – experimental x100% accepted This can be remembered as the “BLT” equation: bigger minus littler over the true value



ErrorSlide73

See “Dimensional Analysis” interactive slide show

Conversions