Introduction to Introduction to ChemistryChemistry

What is Chemistry?What is Chemistry?

•The study of the The study of the composition of matter composition of matter and the changes that and the changes that matter undergoesmatter undergoes

Five major branches Five major branches of chemistryof chemistry

•OrganicOrganic

•InorganicInorganic

•AnalyticalAnalytical

•PhysicalPhysical•BiochemistryBiochemistry

Why study Chemistry???Why study Chemistry???

•Pure ChemistryPure Chemistry•Applied Chemistry Applied Chemistry (Technology)(Technology)

Chemistry plays a Chemistry plays a big part in our livesbig part in our lives•We are in the “Age of We are in the “Age of Plastics”Plastics”

•High “strength to High “strength to weight” ratioweight” ratio

EnergyEnergy•New fuelsNew fuels

•New insulation New insulation materialmaterial

•Energy from the Energy from the sunsun

•Hydrogen cellsHydrogen cells

•Storage batteriesStorage batteries

Medicine and Medicine and BiotechnologyBiotechnology

•MedicinesMedicines•Surgical Surgical breakthroughsbreakthroughs

•Genetic researchGenetic research

AgricultureAgriculture•Protect cropsProtect crops

•Increase food supplyIncrease food supply

•Increase strength and Increase strength and vitality of plantsvitality of plants

EnvironmentEnvironment•PollutionPollution

•Catalytic convertersCatalytic converters

•Acid rainAcid rain

•Ozone layerOzone layer

SCIENTIFIC SCIENTIFIC METHODMETHOD

1. 1. ObservationObservation

Gather data: Gather data: qualitative or qualitative or quantitativequantitative

2. 2. HypothesisHypothesis• tentative tentative explanation for explanation for what is observed what is observed (educated guess)(educated guess)

3. 3. ExperimentsExperiments – – set of controlled set of controlled observations observations that test a that test a hypothesishypothesis

–Independent Independent variable – one variable – one you are going to you are going to changechange

–Dependent – Dependent – changes depending changes depending on the on the independent independent variablevariable

–controlcontrol – standard for – standard for comparisoncomparison

–ModelModel – visual, verbal – visual, verbal and/or mathematical and/or mathematical explanation of explanation of experimental dataexperimental data

ConclusionConclusion

•– – judgment judgment based on the based on the information information obtained obtained

TheoryTheory•– – explanationexplanation that has that has been supported by been supported by MANYMANY experiments experiments

Scientific LawScientific Law

•– – describes a describes a relationship in relationship in nature that is nature that is supported by many supported by many experiments.experiments.

Types of observations

Qualitative observations – describe a substance without using numbers

“It is heavy” “ It is blue” “It smells”

Quantitative observations – use numbers

87 millimeters 10 liters 4.0 g/ml

Scientific Notation

765,000,000,000 7.65 X 1011

Move decimal to the left – is positive

0.0000084 8.4 X 10-6

Move decimal to the right – is negative Samples on handout

Write in standard notation

4.5 x 10-5

0.000045

3.42 x 104

34200

Is how close a measurement is to the correct or accepted value

How close a series of measurements are to each other

(how close a measurement is to other measurements of the same thing)

Dartboard example

Assures the certainty of measurements

For any measurement, scientists only record all the digits they are certain of, plus one estimated figure

Together, they are called “significant figures”

6.2345 meters All the digits are significant.

Which one is the estimated and which are certain?

6,2,3,4 are certain 5 is estimated

A scientist measures 89 seconds

All are significant Which are certain and which are

estimated?

8 is certain 9 is estimated

Rule 1 – all nonzero digits are significant – 1,2,3,4,5,6,7,8,9 – are significant

Rule 2 – Final zeroes to the right of the decimal point are significant

3.4000 5 sig figs

Rule 3 – zeroes between two significant digits are significant

304 3 sig figs 70009 5 sig figs

Rule 4 – zeroes used for spacing the decimal point are not significant

0.00045 2 sig figs 0.02387 4 sig figs

Rule 5 – for numbers in scientific notation, all of the digits before “x 10x” are significant

5.730 x 109 4 sig figs

7000 1 sig fig 7000. 4 sig figs

Let’s practice!!

135.3 4 sig figs 4.6025 5 sig figs 200,035 6 sig figs 0.0000300 3 sig figs

2.0000300 8 sig figs 0.002 1 sig fig 4.44 x 103

3 sig figs 2.0 x 10-2

2 sig figs

10.00 4 sig figs 10 1 sig fig 10. 2 sig figs 102,000 3 sig figs