WELCOME TO CHEMISTRYWELCOME TO CHEMISTRY

What is Chemistry?What is Chemistry?Study of matter and energyMatter= all the “stuff”- anything that has mass or takes up spaceEnergy=what lets us do work (move things)- this includes light, sound, heatEverything is either matter or energyTherefore… it is all chemistry (the “central science”) no matter what they told you in biology!

Branches of ChemistryBranches of Chemistry Analytical chemistryAnalytical chemistry

Answers questions about composition (what is the level of lead in Answers questions about composition (what is the level of lead in that drinking water?)that drinking water?)

Physical chemistryPhysical chemistry Deals with energy transfers in chemical processes (how much Deals with energy transfers in chemical processes (how much

energy is stored in a battery?)energy is stored in a battery?) BiochemistryBiochemistry

Deals with the analysis of chemical processes in living things Deals with the analysis of chemical processes in living things (cellular process such as photosynthesis and respiration)(cellular process such as photosynthesis and respiration)

Organic chemistryOrganic chemistry Study of carbon containing molecules (overlap with biochem)Study of carbon containing molecules (overlap with biochem)

Inorganic chemistryInorganic chemistry Study of the chemistry of nonliving things (geological chemistry, the Study of the chemistry of nonliving things (geological chemistry, the

analysis of the rate of corrosion of metals)analysis of the rate of corrosion of metals) Other areas overlap (geochemistry) as wellOther areas overlap (geochemistry) as well Which branches might be involved in developing a dye for Which branches might be involved in developing a dye for

clothing?clothing?

Pure and Applied ChemistryPure and Applied Chemistry

Pure Chemistry- Pursuit of chemical Pure Chemistry- Pursuit of chemical knowledge for its own sake. (studying it knowledge for its own sake. (studying it because you want to)because you want to)Ex: Nylon Ex: Nylon

Applied Chemistry- research directed to a Applied Chemistry- research directed to a practical goal or applicationpractical goal or applicationEx: researching the commercial use of nylon Ex: researching the commercial use of nylon

Macroscopic vs MicroscopicMacroscopic vs Microscopic

Macroscopic- objects large enough to see Macroscopic- objects large enough to see with an unaided eyewith an unaided eye

Microscopic – objects that could only be Microscopic – objects that could only be seen with an aided eyeseen with an aided eye

Quick review of scientific methodQuick review of scientific method Observations Observations HypothesisHypothesis

TheoryTheory Scientific lawScientific law

EXPERIMENTS

Theory vs Law Theory vs Law

Theory – well tested explanation for a Theory – well tested explanation for a broad set of observations broad set of observations CAN BE CHANGEDCAN BE CHANGED

Law – concise statement that summarizes Law – concise statement that summarizes the results of many observations and the results of many observations and experiements experiements

SI SystemSI System

Agreed upon set of units and measurements- Agreed upon set of units and measurements- used all over the worldused all over the world Except… (which country?)Except… (which country?)

Common base units used by chemists are:Common base units used by chemists are: Kilogram (mass)Kilogram (mass) Meter (length)Meter (length) Kelvin (temperature)Kelvin (temperature) Second (time)Second (time) Mole (amount)Mole (amount)

Prefixes to the SI SystemPrefixes to the SI System Deal with ones we use in classDeal with ones we use in class mega mega (M)(M) = million or 10 = million or 106 6 (factor of 1000000)(factor of 1000000) kilo kilo (k)(k) = thousand or 10 = thousand or 103 3 (factor of 1000)(factor of 1000) deci deci (d)(d) = tenth of 10 = tenth of 10-1 -1 (factor of 0.1)(factor of 0.1) centi centi (c)(c) = hundredth or 10 = hundredth or 10-2 -2 (factor of 0.01)(factor of 0.01) milli milli (m)(m) = thousandth or 10 = thousandth or 10-3 -3 (factor of 0.001)(factor of 0.001) Micro Micro ((μμ)) = millionth or 10= millionth or 10-6 -6 (factor of 0.000001)(factor of 0.000001) nano nano (n)(n) = billionth or 10 = billionth or 10-9 -9 (factor of 0.000000001)(factor of 0.000000001) pico pico (p)(p) = trillionth or 10 = trillionth or 10-12 -12 (factor of 0.000000000001)(factor of 0.000000000001) There are others as well.There are others as well.

MassMassunits and estimationsunits and estimations

Basic SI unit = Basic SI unit = kilogramkilogram (mass of a textbook (mass of a textbook or a brick)or a brick)

gram (g)gram (g) or .001 kg (mass of a small paper or .001 kg (mass of a small paper clip)clip)

milligram (mg)milligram (mg) or .000001 kg (or .001 g) or .000001 kg (or .001 g) (mass of a few grains of salt- many medicine (mass of a few grains of salt- many medicine doses are mg)doses are mg)

microgram (microgram (μμg)g) or .000000001 kg (.000001 g or .000000001 kg (.000001 g or .001 mg) mass of a grain of talcum or .001 mg) mass of a grain of talcum powderpowder

VolumeVolume

The amount of space an object takes The amount of space an object takes upup

Liter (L)Liter (L) and and milliliter (ml)milliliter (ml) are most are most widely used.widely used.

A ml is the same as a cube 1 cm on a A ml is the same as a cube 1 cm on a side (1 cmside (1 cm33 or cubic cm, cc) or cubic cm, cc)

There are 1000 ml to 1 L There are 1000 ml to 1 L 1L = 1000 ml or 1 ml = .001 L1L = 1000 ml or 1 ml = .001 L 1L 1L ≈ 1 quart (1 gallon ≈ 3.8L or 4 L)≈ 1 quart (1 gallon ≈ 3.8L or 4 L) 1 ml = 20 drops, 1 teaspoon = 5 ml1 ml = 20 drops, 1 teaspoon = 5 ml

Volume estimationsVolume estimations

Bathtub holds about 200LBathtub holds about 200LYour car’s gas tank holds about 50-80 LYour car’s gas tank holds about 50-80 LA medicine dropper holds 5 – 10 mlA medicine dropper holds 5 – 10 mlA coffee mug holds about 400 mlA coffee mug holds about 400 ml

LengthLength

Basic unit = meter Basic unit = meter Also widely used are km, cm, mm, Also widely used are km, cm, mm,

μμm and nmm and nm 1000 m = 1 km or 1 m = .001 1000 m = 1 km or 1 m = .001

(1/1000) km(1/1000) km 100 cm = 1 m100 cm = 1 m 10 mm = 1 cm and that means…10 mm = 1 cm and that means… 1m = 1000 mm (or 1 mm = 0.1 cm)1m = 1000 mm (or 1 mm = 0.1 cm)

Length EstimationsLength Estimations

1 km is about 2/3 mile (WHS to Wawa on 1 km is about 2/3 mile (WHS to Wawa on Bethlehem Pike)Bethlehem Pike)

Doorframe = 2 m (a very tall person)Doorframe = 2 m (a very tall person) Ceiling in school is about 3 m highCeiling in school is about 3 m high 1 cm is about the width of a finger1 cm is about the width of a finger 1 mm is about the thickness of a dime1 mm is about the thickness of a dime (Are there about 10 dimes to a finger? (yes)(Are there about 10 dimes to a finger? (yes) 1 1 μμm = size of bacterium (micron)m = size of bacterium (micron) nm = molecules sizes, picometer (pm) atomic nm = molecules sizes, picometer (pm) atomic

nucleusnucleus

TemperatureTemperature ““Official” unit = Kelvin (K)Official” unit = Kelvin (K) Most widely used for measurement = Most widely used for measurement = degrees degrees

Celsius (ºC)Celsius (ºC) Temp in Kelvin = ºC + 273 (º C = K -273)Temp in Kelvin = ºC + 273 (º C = K -273) Examples: ice water = 0 ºC = 273 KExamples: ice water = 0 ºC = 273 K Boiling water = 100 ºC = 373 KBoiling water = 100 ºC = 373 K Body temp = 37 ºC = 310 K (about 99 ºF) Body temp = 37 ºC = 310 K (about 99 ºF) Hot coffee or tea = 85 ºC = 358KHot coffee or tea = 85 ºC = 358K Fridge = 4 ºC = 277 KFridge = 4 ºC = 277 K Very cold day = -15 ºC = 258 K (about 5 ºF)Very cold day = -15 ºC = 258 K (about 5 ºF)

Practice (unit first, then number)Practice (unit first, then number)

Mass of a personMass of a personLength of this hallwayLength of this hallwayMass of a quarterMass of a quarterRoom temperatureRoom temperatureVolume of a “half gallon” milk cartonVolume of a “half gallon” milk cartonVolume of a small cup of juiceVolume of a small cup of juiceHeight of a desktop at schoolHeight of a desktop at schoolLength of a dollar billLength of a dollar bill

AnswersAnswers Mass of a person – about 70 kgMass of a person – about 70 kg Length of this hallway – about 25 mLength of this hallway – about 25 m Mass of a quarter – about 10 gMass of a quarter – about 10 g Room temperature – about 20-25Room temperature – about 20-25ºC (293-298 K)ºC (293-298 K) Volume of a “half gallon” milk carton- about 2 LVolume of a “half gallon” milk carton- about 2 L Volume of a small cup of juice – about 250 mlVolume of a small cup of juice – about 250 ml Height of a desktop at school – about 1mHeight of a desktop at school – about 1m Length of a dollar bill – 15 cm (almost exact) (note Length of a dollar bill – 15 cm (almost exact) (note

that this = 6 inches, so you always have a 6 inch that this = 6 inches, so you always have a 6 inch or 15 cm ruler with you!)or 15 cm ruler with you!)

Some Conversions Some Conversions (the factor label method)(the factor label method)

Use a system and you won’t have to Use a system and you won’t have to guess do I multiply or divide? Or which guess do I multiply or divide? Or which way should I move the decimal place?way should I move the decimal place?

You must know the basic metric prefixesYou must know the basic metric prefixes (kilo, deci, centi, milli, micro)(kilo, deci, centi, milli, micro)First a non metric example:First a non metric example:How many minutes is 450 seconds?How many minutes is 450 seconds? (you need to know the relationship 1 min= (you need to know the relationship 1 min=

60 sec)60 sec)

Factor Label Example # 1Factor Label Example # 1

Start with what you are given: 450 secondsStart with what you are given: 450 secondsUse the known “factor” (known relationship)Use the known “factor” (known relationship)Make the units cancel to give you minutesMake the units cancel to give you minutes450 seconds 1 minute = 7.5 minutes450 seconds 1 minute = 7.5 minutes

60 seconds 60 seconds

The key is to make the units workThe key is to make the units work

PracticePracticeConvert 145 cm to mConvert 145 cm to mYou must know that there are You must know that there are 100 cm to 1 m100 cm to 1 m

145 cm 145 cm 1 m1 m = 1.45 m = 1.45 m

100 cm100 cm

Check to see that the units work.Check to see that the units work.

If the units work, the numbers will too.If the units work, the numbers will too.

17.4 m = how many mm (knowing1m=1000mm)17.4 m = how many mm (knowing1m=1000mm)

17.4 m 17.4 m 1000 mm1000 mm = 17400 mm = 17400 mm

1m1m

More practiceMore practice

Convert 458 mg to gramsConvert 458 mg to gramsYou have to know that 1 g = 1000 mgYou have to know that 1 g = 1000 mgHow do you know what goes on top and How do you know what goes on top and

bottom?bottom?Make the units cancel! (the factor)Make the units cancel! (the factor)

458 mg 1 458 mg 1 gg = 0.458 = 0.458 g (the unit we want)g (the unit we want)

1000 mg1000 mg

A more involved oneA more involved one(non-SI units are (non-SI units are notnot your responsibilityyour responsibilityHow many cm are in 2 miles How many cm are in 2 miles 1 mile = 5280 feet, 1 foot = 12 inches and 1 1 mile = 5280 feet, 1 foot = 12 inches and 1

inch = 2.54 cm (these would be given)inch = 2.54 cm (these would be given)Strategy: miles Strategy: miles feet feet inches inches cm cm

2 miles 5280 feet 12 in 2 .54 cm = 321869 cm2 miles 5280 feet 12 in 2 .54 cm = 321869 cm

1 mile 1 ft 1 in1 mile 1 ft 1 in

You have to practice a bunch of these to get good at them (and you will get good at them)

Really Complex Really Complex

Convert a speed of 35 miles/hour to m/sConvert a speed of 35 miles/hour to m/sGiven: 5280 ft = 1 mile, 1 ft = 12 in, 1 in = 2.54 Given: 5280 ft = 1 mile, 1 ft = 12 in, 1 in = 2.54

cmcmYour responsibility 100 cm = 1m (SI units)Your responsibility 100 cm = 1m (SI units)35 miles 1 hour 1 min 5280 ft 12 in 2.54 cm 1 m =35 miles 1 hour 1 min 5280 ft 12 in 2.54 cm 1 m = 1 hr 60 min 60 sec 1 mile 1 ft 1 in 100 cm1 hr 60 min 60 sec 1 mile 1 ft 1 in 100 cm15.6 m/s (we’ll learn how to handle the number of digits soon)15.6 m/s (we’ll learn how to handle the number of digits soon)How to “punch it in” (follow on board for examples)How to “punch it in” (follow on board for examples)Now go do some for practice! (you need to really know the SI Now go do some for practice! (you need to really know the SI

units)units)

A Few for You to TryA Few for You to Try

Convert 6.7 cm to mConvert 6.7 cm to m

Convert 9.73 mg to cgConvert 9.73 mg to cg

Convert 14675 cm to kmConvert 14675 cm to km

Convert 8.75 kg to mgConvert 8.75 kg to mg

Convert 4500 cg to MgConvert 4500 cg to Mg

Set-up For SolvingSet-up For Solving6.7 cm 1 m = 0.067 m6.7 cm 1 m = 0.067 m 100 cm100 cm9.73 mg 1 cg = 0.973 cg9.73 mg 1 cg = 0.973 cg 10 mg10 mg14675 cm 1 m 1 km = 0.14675 km14675 cm 1 m 1 km = 0.14675 km 100 cm 1000 m100 cm 1000 m8.75 kg 1000 g 1000 mg = 8750000 mg8.75 kg 1000 g 1000 mg = 8750000 mg 1 kg 1 g1 kg 1 g4500 cg 1 g 1 Mg = 0.000045 Mg4500 cg 1 g 1 Mg = 0.000045 Mg 100 cg 1000000g100 cg 1000000g

Scientific (Exponential) NotationScientific (Exponential) NotationA very useful way to describe small and A very useful way to describe small and

large numberslarge numbersNumbers are written as the product of Numbers are written as the product of

some number from 1.0 to 9.99 x 10 to a some number from 1.0 to 9.99 x 10 to a power (power (form of a x 10form of a x 10bb))

Examples (note + exponent = > 1 and – Examples (note + exponent = > 1 and – exponent = <1)exponent = <1)

325 = 3.25 x 10325 = 3.25 x 1022

0.0076 = 7.6 x 100.0076 = 7.6 x 10-3-3

7987.07 = 7.98707 x 107987.07 = 7.98707 x 1033

Practice/ExamplesPractice/Examples

698 =698 = 9.87 x 109.87 x 10-6-6 = = 0.087 =0.087 = 5.67 x 105.67 x 1055

0.000076 =0.000076 = 78700000 =78700000 = 0.00000891 =0.00000891 = 86.3 = 86.3 = 4.82 x 104.82 x 10-8-8 = =

6.98 x 106.98 x 1022

0.000009870.00000987 8.7 x 108.7 x 10-2-2

567000567000 7.6 x 107.6 x 10-5-5

7.87 x 107.87 x 1077

8.91 x 108.91 x 10-6-6

8.63 x 108.63 x 1011

0.00000004820.0000000482

More PracticeMore Practice

6.78 x 106.78 x 10-5-5 = = 0.988 =0.988 =5.90 x 105.90 x 1055== 387000 =387000 =1.8543 x 101.8543 x 10-3-3== 450.98 =450.98 =9.99 x 109.99 x 10-4-4== 5.00 =5.00 =6.23 x 106.23 x 1066== 356.4 =356.4 =7.72 x 107.72 x 10-5-5== 0.000156 =0.000156 =8.78 x 108.78 x 1088 = = 0.076 =0.076 =

The AnswersThe Answers

6.78 x 106.78 x 10-5-5 = = 0.0000678 0.988 = 9.88 x100.0000678 0.988 = 9.88 x10 -1-1

5.90 x 105.90 x 1044==5900059000 387000 =3.87 x10 387000 =3.87 x1055

1.8543 x 101.8543 x 10-3-3= 0.0018543 450.98 = 4.5098 x 10= 0.0018543 450.98 = 4.5098 x 1022

9.99 x 109.99 x 10-4-4== 0.0009990.000999 5.00 = 5.00 x 10 5.00 = 5.00 x 1000

6.23 x 106.23 x 1066==62300006230000 356.4 = 3.564 x 10356.4 = 3.564 x 1022

7.72 x 107.72 x 10-5-5== 0.00007720.0000772 0.00156 = 1.56 x 0.00156 = 1.56 x 1010-3-3

8.78 x 108.78 x 1088 = = 878000000 0.076 = 7.6 x 10878000000 0.076 = 7.6 x 10 -2-2

Multiplying in scientific NotationMultiplying in scientific Notation General rule: (General rule: (aa x 10 x 10bb)()(cc x 10 x 10dd)) = = acac x 10 x 10(b(b +d)+d) Multiply the Multiply the

front partsfront parts and add the and add the exponentsexponentsEx: (4 x 10Ex: (4 x 1022)(2 x10)(2 x1077) = 8 x 10) = 8 x 1099

Ex: (5 x 10Ex: (5 x 1055)(6 x 10)(6 x 1033) = 30 x 10) = 30 x 1088 (oops the “front” is >9.99. (oops the “front” is >9.99.Turn 30 into 3 (down 1 exponent) and add 1 to the exponent Turn 30 into 3 (down 1 exponent) and add 1 to the exponent

to compensate = 3 x 10to compensate = 3 x 1099

On a calculator: 5 EE (or EXP) 5 x 6 EE (or EXP) 3 = and On a calculator: 5 EE (or EXP) 5 x 6 EE (or EXP) 3 = and you’ll see . You “translate” into 3 x 10you’ll see . You “translate” into 3 x 1099).).

Note you don’t punch in x 10Note you don’t punch in x 10–– (times ten to the) (times ten to the) (EE or EXP replaces that)(EE or EXP replaces that)

Learn how to use your calculator!Learn how to use your calculator!

3 09

Dividing in Scientific NotationDividing in Scientific Notation

Similar logic as multiplying except…Similar logic as multiplying except…You divide the front parts and subtract the You divide the front parts and subtract the

exponents:exponents:Ex: (Ex: (55 x 10 x 1044)/()/(22 x 10 x 1055)= 5)= 5/2/2 x 10 x 10(4-5)(4-5) Or 2.5 x 10Or 2.5 x 10-1-1 (which is also 0.25) (which is also 0.25)Ex: (4 x 10Ex: (4 x 1044)/(8 x 10)/(8 x 1022) = 0.5 x 10) = 0.5 x 1022 (oops) (oops)Turn 0.5 into 5 (up 1 place) and Turn 0.5 into 5 (up 1 place) and

compensate by making the exponent 1 compensate by making the exponent 1 less (5 x 10less (5 x 1011) (which = 50)) (which = 50)

On Your CalculatorOn Your Calculator (4 x 10 (4 x 1044)/(8 x 10)/(8 x 1022) )

For this problem you’d punch in:For this problem you’d punch in: (EE and EXP buttons do the same – you’ve got (EE and EXP buttons do the same – you’ve got

one of them!)one of them!) 4 EE 4 and you’ll see 4 EE 4 and you’ll see / (divided by)/ (divided by) 8 EE 2 = and you’ll see8 EE 2 = and you’ll see (or you’re calculator may turn it into 50)(or you’re calculator may turn it into 50) What will your calculator do? Get familiar with it What will your calculator do? Get familiar with it

and you’ll know!and you’ll know!

4 04

5 01

Significant FiguresSignificant Figures No measurements are perfectNo measurements are perfect In any measurement you make you can include In any measurement you make you can include

all numbers that are known plus one additional all numbers that are known plus one additional estimated number.estimated number.

On a car speedometer you can say you are On a car speedometer you can say you are going 62 mph (you know it is 60-something for going 62 mph (you know it is 60-something for sure and the 2 is a good estimate (but you sure and the 2 is a good estimate (but you wouldn’t be shocked if you were really going 61 wouldn’t be shocked if you were really going 61 or 63)or 63)

You can’t go more places than that (62.37 may You can’t go more places than that (62.37 may sound better but that’s all it does.)sound better but that’s all it does.)

Sig Figs RulesSig Figs Rules All nonzero numbers are significant (1,2…9)All nonzero numbers are significant (1,2…9) Zeroes between nonzero numbers are significant Zeroes between nonzero numbers are significant

(the “0” in 406)(the “0” in 406) Leftmost zeroes are never significant (as in 0.005)Leftmost zeroes are never significant (as in 0.005) Rightmost zeroes are significant Rightmost zeroes are significant only only if a decimal if a decimal

point is present (as in 8.900)point is present (as in 8.900) This applies to measured numbers (not counted This applies to measured numbers (not counted

(12 eggs to a dozen) or definitions(12 eggs to a dozen) or definitions Those don’t have measurement uncertaintyThose don’t have measurement uncertainty In general, you can have one more digit (the In general, you can have one more digit (the

estimated one) than your measuring device is estimated one) than your measuring device is marked off tomarked off to

One estimated digitOne estimated digit

Marked of to the nearest wholenumber- estimated to 1 decimal Place. It is definitely 38 point something (the “6” isa good estimate and is trusted).

Marked of to the nearest tenths place- estimated to 2 decimal places. It is definitely 38.5 something (the 7 is a good estimate and is trusted).

Sig figs cont’dSig figs cont’d

698 698 cm has 3 significant figures (shown in cm has 3 significant figures (shown in yellowyellow))0.000.009876 9876 g has 4 significant figures g has 4 significant figures 909.98909.98 ml has 5 significant figures ml has 5 significant figures 0.00000.000077 cg has has 1 significant figure cg has has 1 significant figure9.0009.000 km has 4 significant figures km has 4 significant figures 990 cms has has 1 significant figure 0 cms has has 1 significant figure 90.00090.000 cm/s has 5 significant figures cm/s has 5 significant figures 0.000.00879098000879098000 g/ml has 9 significant figures g/ml has 9 significant figures908908000000 cm has 3 significant figures 000000 cm has 3 significant figures The word significant doesn’t mean important- it means The word significant doesn’t mean important- it means

measured and trustedmeasured and trusted

90 is not 90.000?

So 90 and 90.000 are So 90 and 90.000 are notnot the the same?same?

Mathematically they are equalMathematically they are equal If I weigh a coin on two balances one capable of If I weigh a coin on two balances one capable of

reading to the nearest g and one to the reading to the nearest g and one to the thousandth of a gram, they could both read 90 g thousandth of a gram, they could both read 90 g (one would say 90 and the other 90.000)(one would say 90 and the other 90.000)

The one that reads to a milligram (thousandth) The one that reads to a milligram (thousandth) lets me get more “precision”lets me get more “precision”

Watch the demo of graduated cylinders and of Watch the demo of graduated cylinders and of the marked measuring sticksthe marked measuring sticks

Using Sig Figs in CalculationsUsing Sig Figs in Calculations(multiply/divide)(multiply/divide)

When you multiply or divide your answer can When you multiply or divide your answer can have no more sig figs than the least precise part have no more sig figs than the least precise part of your problem (round as you normally would)of your problem (round as you normally would)

Ex: 489.5 x 3.00 = 1468.5 (can only have Ex: 489.5 x 3.00 = 1468.5 (can only have

So you’d round to 1470 (3 sig figs)So you’d round to 1470 (3 sig figs) It looks like you’re losing accuracy but you’re It looks like you’re losing accuracy but you’re

not. You are making your answer reflect the not. You are making your answer reflect the measurements that went into itmeasurements that went into it

4 sig figs 3 sig figs 3 sig figs (limited by The least precise part

Using Sig Figs in Calculations Using Sig Figs in Calculations (add/subtract)(add/subtract)

Here you are limited by the number of Here you are limited by the number of decimal places:decimal places:

Ex: 5.9Ex: 5.990 90 (3 places)(3 places) +7.8 (1 place)+7.8 (1 place)= 13.8 (13.79 rounded to 1 decimal place) = 13.8 (13.79 rounded to 1 decimal place)

(1 decimal place limits you)(1 decimal place limits you)

Sig Fig Calculation PracticeSig Fig Calculation Practice

5.64 x 3.877 = 21.9 (21.866... rounded to 3 sig 5.64 x 3.877 = 21.9 (21.866... rounded to 3 sig figs)figs)

4.999 + 1.2 = 6.2 (6.199 rounded to 1 decimal 4.999 + 1.2 = 6.2 (6.199 rounded to 1 decimal place (add/subtract has diferent rules)place (add/subtract has diferent rules)

(4.77 + 8.2)/6.88 = 13.0/6.88 = 1.89(4.77 + 8.2)/6.88 = 13.0/6.88 = 1.89 (4.1 x 10(4.1 x 1033)(1.6772 x 10)(1.6772 x 1022) = 6.9 x 10) = 6.9 x 1055 or 69000 or 69000

(not 68765.2)(not 68765.2) Extra digits look good but they aren’t worth Extra digits look good but they aren’t worth

muchmuch

Accuracy and PrecisionAccuracy and PrecisionAccuracy = “correctness”Accuracy = “correctness”Precision = consistency of a set of Precision = consistency of a set of

measurements (1 measurement is not measurements (1 measurement is not precise)precise)

Field Goal ex: If you are always wide to Field Goal ex: If you are always wide to the right, you are precise (consistent) but the right, you are precise (consistent) but not accuratenot accurate

A watch that is always fast by 5 minutes is A watch that is always fast by 5 minutes is precise, but not accurateprecise, but not accurate

Accuracy and PrecisionAccuracy and Precision

Wrap-Up of Unit 1Wrap-Up of Unit 1

Lots of stuff hereLots of stuff hereGet used to your calculator. Bring it to Get used to your calculator. Bring it to

class daily and practice with the calculator class daily and practice with the calculator you’ll use on the tests.you’ll use on the tests.

Test study hint- use the “chapter study Test study hint- use the “chapter study guide” sheet as a checklist. There will be guide” sheet as a checklist. There will be notes, homework and practice on just notes, homework and practice on just about everything. Ask questions if needed. about everything. Ask questions if needed. Come in and get help. It is chemisCome in and get help. It is chemistrytry..