Chapter 1Chapter 1

ChemistryChemistry – – the study of all substances and the changes they the study of all substances and the changes they

can undergo.can undergo.

Scientific Method-Scientific Method- ObservationObservation Stating a QuestionStating a Question Hypothesis – possible answerHypothesis – possible answer ExperimentExperiment Conclusion – what you found in your Conclusion – what you found in your

experiment experiment

Scientific method leads to Scientific method leads to Natural LawNatural Law – Tells you how nature – Tells you how nature

behaves but not why it behaves.behaves but not why it behaves. Finally you form a Finally you form a TheoryTheory – Explains why nature behaves – Explains why nature behaves

in the way described by natural law.in the way described by natural law. Used for prediction of results for Used for prediction of results for

further experiments. further experiments.

During the experiment…During the experiment… Experimental Control Experimental Control - Factor - Factor

that remains constant during the that remains constant during the experiment. It is compared with experiment. It is compared with the variable.the variable.

Variable Variable - Factor that is being - Factor that is being tested during the experiment.tested during the experiment.

Measurement…Measurement… When we perform When we perform

experiments, we need to use experiments, we need to use some form of measurement.some form of measurement.

Metric System – International Metric System – International set of units (SI)set of units (SI)

Base units-Base units- Mass = kilogram (kg)Mass = kilogram (kg) Length = meter (m)Length = meter (m) Time = seconds (s)Time = seconds (s) Count, quantity = mole (mol)Count, quantity = mole (mol) Temperature = Kelvin (K)Temperature = Kelvin (K) Electric Current = ampere (A)Electric Current = ampere (A) Luminous intensity = candela (cd)Luminous intensity = candela (cd)

Derived Units – made from Derived Units – made from combining 2 or more base units. combining 2 or more base units.

Ex. Area = length x width = Ex. Area = length x width = mm22

Volume = length x width Volume = length x width x x height = cmheight = cm33

Density = mass / volume Density = mass / volume = = g/cmg/cm33

Exceptions to SI units… Exceptions to SI units… Volume = liter (L)Volume = liter (L) Pressure = atmosphere Pressure = atmosphere

millimeter millimeter of Hg (atm mm Hg)of Hg (atm mm Hg) Aka PascalAka Pascal Temperature = Celsius degree Temperature = Celsius degree

(C(Coo)) Energy = Calorie (cal)Energy = Calorie (cal)

Reliability in MeasurementReliability in Measurement Accuracy vs. Precision Accuracy vs. Precision PrecisionPrecision – Measurement that – Measurement that

gives the same result again and gives the same result again and again under the same conditionsagain under the same conditions

AccuracyAccuracy – Measurement that – Measurement that is close to the accepted value.is close to the accepted value.

Significant Digits – Defined as Significant Digits – Defined as certain digits and the estimated digit certain digits and the estimated digit of a measurement. of a measurement.

Rules for determining sig. Digs.Rules for determining sig. Digs. ““0”s as placeholders are 0”s as placeholders are NOT NOT

significant!significant! Ex. 1040 g or 0.0064 mEx. 1040 g or 0.0064 m

Atlantic – Pacific Rule Atlantic – Pacific Rule If the decimal is If the decimal is PPresent, count resent, count

from the Pacific side (left) from the Pacific side (left) beginning with the first non-zero beginning with the first non-zero digitdigit

If the decimal is If the decimal is AAbsent, count bsent, count from the Atlantic side beginning from the Atlantic side beginning with the first non-zero digit.with the first non-zero digit.

How many significant Digits are How many significant Digits are present?present?1700 cm1700 cm0.00960 kg0.00960 kg64050 L64050 L45.00 mg45.00 mg0.0607 m0.0607 m

How many sig. digs. are How many sig. digs. are present?present?10100 mL10100 mL0.50090 dg0.50090 dg6.60 x 106.60 x 10-8-8

mLmL2.00 x 102.00 x 1033 g g 4. 010 x 104. 010 x 1044 L L

Calculation rules for Sig. Digs.Calculation rules for Sig. Digs. Multiplication and DivisionMultiplication and Division

The measurement with the The measurement with the SMALLEST NUMBER OF SIG. SMALLEST NUMBER OF SIG. DIGS. Determines how many DIGS. Determines how many digits are allowed in the answer.digits are allowed in the answer.

Ex. 4.3 x 6.45 will have 2 sig. Ex. 4.3 x 6.45 will have 2 sig. digs. in the answer.digs. in the answer.27.735 = 2827.735 = 28

Addition and SubtractionAddition and Subtraction The number of significant digits The number of significant digits

is dependent upon or rounded off is dependent upon or rounded off to the measurement with the to the measurement with the largest uncertainty. ***Use the largest uncertainty. ***Use the least amount of decimal spots***least amount of decimal spots***

Ex. 6.45 + 2.36 + 4.6 = Ex. 6.45 + 2.36 + 4.6 = 13.41 rounded to 13.4 13.41 rounded to 13.4

Scientific NotationScientific Notation Why use it?Why use it? Distance from the sun = Distance from the sun =

93,000,000 miles93,000,000 miles Al strip = 4.12 g contains 1.2 x Al strip = 4.12 g contains 1.2 x

10102323 atoms atoms

Rules for Scientific NotationRules for Scientific NotationExpress the same number of Express the same number of

significant digitssignificant digitsKeep one digit to the left of the Keep one digit to the left of the

decimal pointdecimal pointMultiplication and Division, Multiplication and Division,

add the number of exponents add the number of exponents

Simplify the following:Simplify the following: (4.2 x 10(4.2 x 1066)(1.1 x 10)(1.1 x 10-2-2))

2.3 x 102.3 x 1022

(5.0 x 10(5.0 x 1055)(1.2 x 10)(1.2 x 1011))

9.0 x 109.0 x 101010

2.0 x 10^22.0 x 10^2 6.7 x 10^-56.7 x 10^-5

Factor-Label Method/ Dimensional Factor-Label Method/ Dimensional AnalysisAnalysis

Problem Solving MethodProblem Solving Method Treat units as factors, which can be Treat units as factors, which can be

cancelledcancelled Must know your Must know your

equalities/conversion factorsequalities/conversion factors Choose the equality that cancels out Choose the equality that cancels out

the original unitthe original unit

Steps:Steps: 1) Begin with known1) Begin with known 2) Decide upon equality (write 2) Decide upon equality (write

this near the problem)this near the problem) 3) Arrange units to cancel out 3) Arrange units to cancel out

originaloriginal 4) Do the math!4) Do the math!

How many seconds are in 4 How many seconds are in 4 hours?hours?

How many kilograms are in 5 How many kilograms are in 5 g?g?

Change 286 cg to Mg.Change 286 cg to Mg.

To change from English to To change from English to Metric units, use chart on page Metric units, use chart on page 38.38.

How many inches are in 354 How many inches are in 354 cm?cm?

Ratios – common method of Ratios – common method of expressing results and/or expressing results and/or measurement in chemistrymeasurement in chemistry

Similar to a fractionSimilar to a fraction Units in numerator and Units in numerator and

denominatordenominator

Ex.Ex. Speed = mphSpeed = mph Lunchmeat = dollars/lbLunchmeat = dollars/lb Density = g/cmDensity = g/cm33 or g/mL or g/mL Population Density = people/kmPopulation Density = people/km22

Pressure = psi or p/inPressure = psi or p/in22

Most substances-Solid forms sink Most substances-Solid forms sink in its own liquid because solid in its own liquid because solid form is more dense.form is more dense.

EXCEPTION- Water.EXCEPTION- Water. The freezing point of water is 0 The freezing point of water is 0

degrees C.degrees C. Solid ice floats in liquid water.Solid ice floats in liquid water. Water is most dense at 4 degrees C.Water is most dense at 4 degrees C.

What would happen if ice did not What would happen if ice did not float to…float to…

The ocean?The ocean? It would freezeIt would freeze

The earth’s temperature?The earth’s temperature? It would decreaseIt would decrease

The icebergs?The icebergs? They would sink and never meltThey would sink and never melt

The earth?The earth? It would freezeIt would freeze

Life?Life? It would cease to existIt would cease to exist

Solid DensitySolid Density Used to find the density of solid Used to find the density of solid

objects.objects. Regular geometric shapes vs. Regular geometric shapes vs.

irregular shapes.irregular shapes.

Liquid DensityLiquid Density The density of waterThe density of water

1g/mL @ 4 degrees C1g/mL @ 4 degrees C Other fluids have different Other fluids have different

densitiesdensities Oil floats on waterOil floats on water

Density – mass per unit of Density – mass per unit of volumevolume

Ex.Ex. Zinc CylinderZinc Cylinder Diameter is 1.22 cmDiameter is 1.22 cm Height = 3.28 cmHeight = 3.28 cm Mass = 28.79gMass = 28.79g

V= V= ∏r² h ∏r² h h= 3.14 x (0.61cm)² x 3.28cm h= 3.14 x (0.61cm)² x 3.28cm

=3.83cm³=3.83cm³ V= 3.83 cmV= 3.83 cm33

M= 28.79 gM= 28.79 g D= m/v = 28.79g/3.83cm³ D= m/v = 28.79g/3.83cm³

=7.52g/cm=7.52g/cm33