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Welcome to AP Chemistry pp

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Ch. 1 Significant figures Meaningful digits in a MEASUREMENT

Exact numbers are counted, have unlimited significant figures

If it is measured or estimated, it has sig figs.

If not it is exact . . . All numbers except zero are significant. Some zeros are, some aren’t

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Which zeroes count? pp

In between other sig figs does Before the first number doesn’t After the last number counts if it is after the decimal point the decimal point is written in 3200 2 sig figs

3200. 4 sig figs

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Which zeroes count? Atlantic Pacific Rule Decimal point Present, use Pacific

Ocean E.g., 0.002540 Decimal point Absent, use Atlantic

Ocean E.g., 2540

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Doing the math pp

Multiplication and division, same number of sig figs in answer as the least in the problem

Addition and subtraction, same number of decimal places (vs. sig figs) in answer as least in problem.

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More Preliminaries

Scientific Method

Metric System

Uncertainty

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Scientific method. A way of solving problems Observation - what is seen or measured Hypothesis - educated guess of why

things behave the way they do. (possible explanation)

Experiment - designed to test hypothesis leads to new observations, and the cycle goes on

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Scientific method. After many cycles, a broad, generalizable

explanation is developed for why things behave the way they do.

This is a Theory Also, a regular pattern of how things

behave the same in different systems emerges.

This is a Law Laws are summaries of observations

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Scientific method. Theories have predictive value. The true test of a theory is if it can

predict new behaviors. If the prediction is wrong, the theory

must be changed. Theory is the why Law is the how

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Observations

Hypothesis

Experiment

Law

Theory(Model)

Prediction

Experiment

Modify

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Metric System Every measurement has two parts: Number Scale (unit) SI system (le Systeme International) is based

on the metric system. Prefix + base unit Prefix tells you the power of 10 to multiply by -

decimal system - easy conversions

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Metric System Base Units Mass - kilogram (kg) Length - meter (m) Time - second (s) Temperature - Kelvin (K) Electric current- ampere (amp, A) Amount of substance - mole (mol)

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Prefixes pp

Giga - G 1,000,000,000 109

mega - M 1,000,000 106

kilo - k 1,000 103

deci - d 0.1 10-1

centi - c 0.01 10-2

milli - m 0.001 10-3

micro - m 0.000001 10-6

nano - n 0.000000001 10-9

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Deriving the Liter Liter is defined as the volume of 1 dm3 gram is the mass of 1 cm3

1 ml = 1 cm3

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Figure 1.3Measurement of Volume

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Mass and Weight Mass is measure of resistance to

change in motion Weight is force of gravity. Sometimes used interchangeably Mass can’t change, weight can

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Uncertainty Basis for significant figures All measurements are uncertain to

some degree Precision - how repeatable Accuracy - how correct - closeness to

true value. Random error - equal chance of being

high or low - addressed by averaging measurements - expected

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Figure 1.4Common Types of

Laboratory Equipment Used to Measure Liquid

Volume

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Figure 1.6Measurement of Volume Using a BuretThe volume is read at the bottom of the liquid curve (called the meniscus).

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Uncertainty

Systematic error - same direction each time

Want to avoid this Better precision implies better accuracy you can have precision without

accuracy You can’t have accuracy without

precision

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Figure 1.7 The Difference between Precision and Accuracy

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Dimensional Analysis

Using the units to solve problems

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Dimensional Analysis Use conversion factors to change the units Conversion factors = 1 1 foot = 12 inches (equivalence statement) 12 in = 1 = 1 ft.

1 ft. 12 in

2 conversion factors multiply by the one that will give you the

correct units in your answer.

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Examples 11 yards = 2 rod 40 rods = 1 furlong 8 furlongs = 1 mile The Kentucky Derby race is 1.25 miles.

How long is the race in rods, furlongs, meters, and kilometers?

A marathon race is 26 miles, 385 yards. What is this distance in rods, furlongs, meters, and kilometers?

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Examples Science fiction often uses nautical

analogies to describe space travel. If the starship U.S.S. Enterprise is traveling at warp factor 1.71, what is its speed in knots?

Warp 1.71 = 5.00 times the speed of light speed of light = 3.00 x 108 m/s 1 knot = 2000 yd/h exactly

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Apothecaries (druggists) use the following set of measures in the English system:

20 grains ap = 1 scruple (exact) 3 scruples = 1 dram ap (exact) 8 dram ap = 1 oz. ap (exact) 1 dram ap = 3.888 g 1 oz. ap = ? oz. troy What is the mass of 1 scruple in grams?

Examples

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Examples The speed of light is 3.00 x 108 m/s.

How far will a beam of light travel in 1.00 ns?

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Temperature and Density

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Temperature A measure of the average kinetic

energy Different temperature scales, all are

talking about the same height of mercury.

Derive a equation for converting ºF toºC

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0ºC 32ºF

0ºC = 32ºF

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100ºC 212ºF

100ºC = 212ºF

0ºC 32ºF

0ºC = 32ºF

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100ºC 212ºF0ºC 32ºF

100ºC = 212ºF0ºC = 32ºF

100ºC = 180ºF

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100ºC 212ºF0ºC 32ºF

100ºC = 212ºF0ºC = 32ºF

100ºC = 180ºF1ºC = (180/100)ºF1ºC =

9/5ºF

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ºC

ºF

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ºC

ºF

(0,32)= (C1,F1)

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ºC

ºF

(0,32) = (C1,F1)

(120,212) = (C2,F2)

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Celsius/Fahrenheit Conversions

Y - intercept is at 32 degrees F Tc = 5/9(Tf - 32)

Tf = (9/5 x Tc) + 32

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Figure 1.8The Three Major Temperatu

re Scales

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Figure 1.9Normal Body Temperature on the Fahrenheit, Celsius, and Kelvin

Scales

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Density Ratio of mass to volume D = m/V Useful for identifying a compound Useful for predicting weight An intrinsic property- does not depend

on what the material is

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Density Problem An empty container weighs 121.3 g. Filled

with carbon tetrachloride (density 1.53

g/cm3 ) the container weighs 283.2 g. What is the volume of the container?

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Density Problem A 55.0 gal drum weighs 75.0 lbs. when

empty. What will the total mass be when filled with ethanol?

density 0.789 g/cm3 1 gal = 3.78 L 1 lb = 454 g

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Matter:Matter: Anything Anything

occupying space occupying space and having mass.and having mass.

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Classification of Matter

Three States of Matter:Three States of Matter:

– Solid: rigid - fixed volume and shapeSolid: rigid - fixed volume and shape

– Liquid: definite volume but assumes Liquid: definite volume but assumes the the shape of its containershape of its container

– Gas: no fixed volume or shape - Gas: no fixed volume or shape - assumes assumes the shape of its containerthe shape of its container

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Types of Mixtures

Mixtures have variable Mixtures have variable composition.composition.

AA homogeneous mixturehomogeneous mixture is a is a solution (for example, vinegar)solution (for example, vinegar)

AA heterogeneous mixtureheterogeneous mixture is, to the is, to the naked eye, clearly not uniform (for naked eye, clearly not uniform (for example, a bottle of ranch dressing)example, a bottle of ranch dressing)

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Pure Substances

Can be isolated by separation Can be isolated by separation methods:methods:

ChromatographyChromatography FiltrationFiltration DistillationDistillation

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Figure 1.10Simple Laboratory Distillation Apparatus

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Element:Element: A substance that A substance that cannot be decomposed into cannot be decomposed into simpler substances by chemical simpler substances by chemical means.means.

Compound:Compound: A substance with a A substance with a constant composition that can be constant composition that can be broken down into elements by broken down into elements by chemical processes.chemical processes.

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Figure 1.13The Organization of

Matter