chapter 3 scientific measurements. describe the following object in your notes
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Chapter 3Chapter 3
Scientific MeasurementsScientific Measurements
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Describe the following object in Describe the following object in your notesyour notes
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Qualitative vs. QuantitativeQualitative vs. QuantitativeQualitative:Qualitative: gives results in a descriptive gives results in a descriptive
nonnumeric formnonnumeric form
Ex: large & small Ex: large & small
Quantitative:Quantitative: gives results in a definite gives results in a definite form, usually in numbersform, usually in numbers
Ex: 121cmEx: 121cm
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Accuracy vs. PrecisionAccuracy vs. PrecisionAccuracy:Accuracy: is a measure of how close a is a measure of how close a
measurement comes to the actual or measurement comes to the actual or true value.true value.
CorrectnessCorrectness
Poor accuracy results from procedural or Poor accuracy results from procedural or equipment flawsequipment flaws
Good accuracy
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Accuracy vs PrecisionAccuracy vs PrecisionPrecision:Precision: is a measure of how close a is a measure of how close a
series of measurements are to one series of measurements are to one another.another.
ReproducibilityReproducibility
Poor precision results from poor Poor precision results from poor techniquetechnique Good
precision
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Determining ErrorDetermining Error
100 x value accepted
value acceptedvalue alexperimentError Percent
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100 x value accepted
value acceptedvalue alexperimentError Percent
What is the percent error of a measured value of 114 lbs if the
person’s actual weight is 107 lbs?
7%
100 107
107114
ErrorPercent
xErrorPercent
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Scientific NotationScientific Notation
Used when working with large or very Used when working with large or very small numberssmall numbers
#’s less than 1 have negative exponents#’s less than 1 have negative exponents 0.00036 = 3.6 x 100.00036 = 3.6 x 10-4-4
#’s greater than 1 have positive #’s greater than 1 have positive exponentsexponents 36,000 = 3.6 x 1036,000 = 3.6 x 1044
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DO NOW: Significant FiguresDO NOW: Significant FiguresSig.Figs.
Sci. Notation
1. 0.00341 3 3.41 x 10-3
2. 1.0040 5 1.0040 x 100
3. 0.00005 1 5 x 10-5
4. 65000 2 6.5 x 104
5. 40300 3 4.03 x 104
6. 200300 4 2.003 x 105
7. 0.0500 3 5.00 x 10-2
8. 2.420 x 1012 4 done
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DO NOW: Significant FiguresDO NOW: Significant Figures
5.910 x 1084591,000,000 L5.
8.8 x 10328792 L4.
6164.32 x 10-1 dm3.
1.8 x 10-320.00177 cm2.
3.147 x 1024314.721 m1.
Wrong measurements correct Correct Answers sig. figs.
The following measurements are not in the correct sig. figs. Rewrite them so that they show the correct number of sig. figs. Put all answers in scientific notation.
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Dimensional analysisDimensional analysis
The skill of converting from one unit The skill of converting from one unit to anotherto another
EX: EX: 10 meters is how many 10 meters is how many millimetersmillimeters
13 days is how many seconds13 days is how many seconds
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Units Get Larger (always make larger Units Get Larger (always make larger unit = 1)unit = 1)
KKatie atie HHates ates DDogs b/c ogs b/c DDogs ogs CCan’t an’t MMeoweow
101033 101022 101011 BASE BASE UNIT UNIT metemete
rrliterliter
GramGram
1010-1-1 1010-2-2 1010-3-3
kilokilo hectohecto decadeca decideci centicenti millimilli
1,0001,000mmin in
1 km1 km
100m100min in
1 hm1 hm
10 m10 minin
1dam1dam
10 10 dmdminin
1m1m
100c100cmminin
1 m1 m
1,000m1,000mmminin
1m1m
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Conversion FactorConversion Factor A fraction that always equals 1.A fraction that always equals 1.
EX: EX: 1km = 1,000m 1km = 1,000m put into a fractionput into a fraction
1 km 1 km or or 1,000m1,000m1,000m 1 km1,000m 1 km
Both fractions equal 1Both fractions equal 1
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EXAMPLEEXAMPLEProblem #1:Problem #1: 12 m=?cm 12 m=?cmSTEPSSTEPS1. Write the given 1. Write the given 12m12m2. Draw the conversion line 2. Draw the conversion line 12m12m
3. Find a conversion factor. 3. Find a conversion factor. 100cm = 1m100cm = 1m
4. Place what unit you want to get rid of 4. Place what unit you want to get rid of opposite the given.opposite the given.
12m12m
mm
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5. Place the unit you want at the same level 5. Place the unit you want at the same level as the given.as the given. 12m12m cm cm
mm 6. Fill in the #’s of the conversion factor.6. Fill in the #’s of the conversion factor.
12m12m 100 cm 100 cm
11 mm
7. Cancel units 7. Cancel units 12m12m 100 cm 100 cm
11 mm 8. Multiply everything on top, multiply 8. Multiply everything on top, multiply
everything on the bottom, and then divideeverything on the bottom, and then divide SO……….12m = 1,200cmSO……….12m = 1,200cm
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Chapter 17Chapter 17
ThermochemistryThermochemistry
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ThermochemistryThermochemistry
The study of energy changes that The study of energy changes that occur during chemical reactions and occur during chemical reactions and
changes in state.changes in state.
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ThermochemistryThermochemistry
EnergyEnergy: the ability to do work or to supply : the ability to do work or to supply heatheat
ENERGY (Joule or calorie) = HEAT (J or cal)ENERGY (Joule or calorie) = HEAT (J or cal)
1 cal = 4.18 J1 cal = 4.18 J
Chemical Potential EnergyChemical Potential Energy: stored energy : stored energy in in
chemicalschemicals
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Heat vs. Temp.Heat vs. Temp.
Heat and temperature are concepts Heat and temperature are concepts that are often confused that are often confused
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Heat vs. Temp.Heat vs. Temp.
Amount of energy in a Amount of energy in a systemsystem
Degree of hotness or Degree of hotness or coldness of an objectcoldness of an object
Form of energyForm of energy Measures the average Measures the average kinetic energy of kinetic energy of moleculesmolecules
Flows from a warmer Flows from a warmer object to a cooler oneobject to a cooler one
It is measured in Joules It is measured in Joules or caloriesor calories
It is measured in It is measured in degreesdegrees
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Calorie vs. calorieCalorie vs. calorie
Calorie = refers to food (dietary)Calorie = refers to food (dietary)
Calorie = 1kilocalorie = 1,000 caloriesCalorie = 1kilocalorie = 1,000 calories
Snickers Bar = 280 Calories = 280 kilocaloriesSnickers Bar = 280 Calories = 280 kilocalories = 280,000 calories= 280,000 calories
calorie= a unit of heatcalorie= a unit of heat
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Specific Heat CapacitySpecific Heat Capacity
The amount of heat it takes to raise the The amount of heat it takes to raise the temperature of 1 g of a substance 1temperature of 1 g of a substance 1ooCC
q =m q =m ΔΔT CT Cpp
q =heat energy (J or cal) q =heat energy (J or cal)
m =mass (g) m =mass (g) ΔΔT =(TT =(Tff – T – Tii) = ) = ooCC CCpp = specific heat = = specific heat =
J = heat (J)J = heat (J) g x g x ooC mass (g) x (TC mass (g) x (Tff – T – Tii) )
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Q =m Δ T CQ =m Δ T Cpp
q = g q = g ooC J C J
g x g x ooC C
When units are canceled, q = JoulesWhen units are canceled, q = Joules
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Specific Heat CapacitySpecific Heat Capacity
The amount of heat it takes to raise the The amount of heat it takes to raise the temperature of 1 g of a substance 1temperature of 1 g of a substance 1ooCC
For example: For example: WATER VS. METALWATER VS. METAL
-Higher the specific heat: the less -Higher the specific heat: the less fluctuation of fluctuation of
heat and therefore the less fluctuation of heat and therefore the less fluctuation of the the
temp. of the object.temp. of the object.WaterWater IronIron
4.18 J/(g x 4.18 J/(g x ooC)C) 0.46 J/(g x 0.46 J/(g x ooC)C)
HighHigh LowLow
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Exothermic vs. EndothermicExothermic vs. Endothermic
Exothermic: a process in which heat is released Exothermic: a process in which heat is released to the surroundingto the surrounding
- The system loses heat as the surroundings The system loses heat as the surroundings heat upheat up
- q has a negative value because the system is q has a negative value because the system is losing heatlosing heat
Endothermic: a process in which the system Endothermic: a process in which the system gains heat as the surroundings cool downgains heat as the surroundings cool down
- Heat flows into a systemHeat flows into a system- q has a positive value because the system is q has a positive value because the system is
gaining heatgaining heat
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CalorimetryCalorimetry
To measure specific heat capacity a To measure specific heat capacity a bomb calorimeter is used.bomb calorimeter is used.
Calorimetry is based on the principle:Calorimetry is based on the principle:
Law of conservation of energyLaw of conservation of energy
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Bomb Bomb CalorimeterCalorimeter
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Plastic Cup Plastic Cup CalorimeterCalorimeter