chemistry ch 1.pptx

8/14/2019 Chemistry ch 1.pptx

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Chapter 1 Basic Concepts of Chemistry

1.1 Chemistry and its Methods

Hypothesis: A tentative explanation or predictionbased on experimental observations.

Law: A concise verbal or mathematical statement

of a behavior or a relation that seems always tobe the same under the same conditions.

Theory: a well-tested, unifying principle that

explains a body of facts and the laws based onthem. It is capable of suggesting new hypotheses

that can be tested experimentally.


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States of

matter

rigidity Expansion

on heating

compressibility

Solid Rigid Slight SlightLiquid Flows and

assumes

shape ofcontainer

Slight Slight

Gas Fills any

containercompletely

Expands

infinitely

Easily

compressed


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States of Matter and Kinetic-Molecular Theory

All matter consists of extremely tiny particles

that are in constant motion.Solids: are packed closely and in a regular array

Liquids: (considered fluid) are arranged

randomly rather than in a pattern

Gases: (considered fluid), particles of gas are far

apart, move extremely rapidly and not

constrained by their neighbors, fill container

The higher the temperature (T), the faster

the particles move.


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Pure substance

A pure substance cannot be separated into 2 or

more different species by any physical techniqueat ordinary temperatures (T).


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Mixtures: Homogeneous and heterogeneous

A mixture consists of 2 or more pure substances

that can be separated by physical techniques.

Heterogeneous: the properties in a region are

different from those in another region, example,sand at the beach, milk. See next slide

Homogeneous: mixture consists of 2 or moresubstances in the same phase, often called

solution, examples, air, gasoline


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milk

Water (H2O)


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1.4 Elements

Composed of only one type of atom.

An atom is the smallest particle of an elementthat retains the characteristic chemical

properties of that element.

Know the elements. Derived mostly fromLatin, Greek, German, etc. (named after people,

countries, planets, etc)


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Na: sodium (Latin, Natrium)

K: potassium (Latin, Kalium)

Pb: lead (Latin, plumbum meaning heavy)

He: helium (Greek, helios, sun)

Ag: silver (Latin, argentum)

Au: gold (Latin, aurum)

Fe: iron (Latin, ferrum)

Cu: copper (Latin, cuprum)W: tungsten (German, Wolfram)

Clicker Q: What is symbol for hydrogen?


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1.5 Compounds

A pure substance like sugar, salt or water, which

is composed of 2 or more different elementsheld together by chemical bonds is a chemical

compound. No limit to the # of compounds

there appears to be.


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1.6 Physical Properties

Properties that can be observed and measured

without changing the composition of asubstance. Examples: color, mp, bp, density,

state (s,l,g), solubility, electric conductivity,

malleability, ductility, viscositySee next slide

Density = mass / volume


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Extensive and intensive properties

Extensive property: depends on the amount of a

substance present. Example: Mass and volume

Intensive property: does not depend on the

amount of a substance present. Example: mp,bp, density


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1.7 Physical and Chemical Changes

Changes in physical properties are called physical

changes. The identity of the substance ispreserved even though it may have changed its

physical state or gross size. Melting, vaporization

etc.

Chemical change: one or more substances

(reactants) are transformed into one or more

different substances (products)


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Chemical equation showing chemical change.


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1.8 Energy: Some Basic

Principles

Definition: capacity to do work.

Energy can be classified as

kinetic or potential.

Kinetic energy is energy

associated with motion.

Potential energy results from an

objects position.


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Conservation of Energy

Law of Conservation of Energy states that

energy can neither be created nor destroyed(the total energy of the universe is constant).


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The tools of quantitative chemistry

1 units of measurement

Metric system is the scientific system used.SI: International System of Units (Systme

International dUnits)


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Temperature Scales


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The Celsius Temperature Scale (C)

Celsius, a Swedish astronomer (early 1700s)

Water freezes at (clicker Q:just input the number)and boils at (clicker Q:just input the number).

The Kelvin Temperature Scale (K)Named after William Thomson known as Lord

Kelvin. Also known as absolute 0. Absolute 0 is 0K

which is -273C. Kelvin scale doesnt put behindnumber. Kelvin and Celsius degrees are the same

size (see next slide).


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The Fahrenheit Temperature Scale (F)

Devised by Gabriel Fahrenheitearly 1700s -

(German instrument maker)C = (F-32) / 1.8 F = 1.8 x C + 32

Conversions:

Clicker Q: 85F is what in Celsius?


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Conversion from one to the other.

25C is how many kelvins?

Clicker Q: 38C is how many kelvins?

400 K is how many C

Clicker Q: 1000 K is how many C?


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Length, Volume, and Mass

Length

Meter is the standard unit of length.

1 m = 100 cm 1000 m = 1 km 1 in = 2.54 cm

Conversions

Clicker Q: 1 cm is how many mm?


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Table R-2, p. 26

Know these.


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Volume

1 liter = 1000 ml = 1000 cm3 1 gal = 3.785 l

So 1 ml = 1 cm3 (used in medicine, cc)1 dl = 100 ml widely used in medicine

Conversions

Clicker Q: How many liters are in 750 ml?


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Mass

SI unit is the kg

1 kg = 1000 g 1 g = 1000 mg 1 lb = 454 g1 kg = 2.205 lbs

Conversions.

Clicker Q: how many g are in 540 mg?


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Energy units

SI unit is the joule (J)

1 J = 1 kgm2/s2 1 J = 4.184 calories1000 J = 1 kJ

Dietary calorie is actually 1000 kcal usuallyabbreviated Cal

Interesting: How do we determine the caloriecontent of food? Atwater system: 1 g protein, 1 g

carbohydrate = 4 kcal, 1 g of fat = 9 kcal, 1 g ofalcohol = 7 kcal

Clicker Q: 2300 J is how many kJ


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2 Making Measurements: Precision, Accuracy,

and Experimental Error

Theprecisionof a measurement indicates howwell several determinations of the same

quantity agree.

Accuracyis the agreement of a measurementwith the accepted value of the quantity.

Accuracy is often reflected by Experimental

error.

=

Experimental value Accepted valuePercent Error 100

Accepted value


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The precision of a measurement indicates how well

several determinations of the same quantity agree.


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3 Mathematics of Chemistry

Exponential or Scientific Notation

Scientific notation is used to present very large

or very small numbers.


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Clicker Q: Express this number in normalnotation 1.23 x 103

Clicker Q: Express this number in normal

notation 1.23 x 10-3


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Significant figures: The number of digitsrepresented in a number conveys the precision ofthe number or measurement.

A mass measured to 0.1g is far less precise than a

mass measured to 0.0001g.1.1g vs. 1.0001g

(2 sig. figs. vs. 5 sig. figs)

In order to be successful in this course, you willneed to master the identification and use ofsignificant figures in measurements andcalculations!

Significant Figures


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Significant figures

Exact numbers: number of eggs in a dozen, # of

people in a locked roomSignificant figures indicate the uncertainty in

measurements.

See next slides


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36

1 2 3 4 5 6 7 8 9 10 11 12 13 14

1

2

3

4

5

6

7

8

9


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38

Clicker Q: How wide is the paper to the best

of your ability to measure it?

7

8

9

Rules for sig figs


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Rules for sig figs

1. Nonzero digits are always significant.

123.2 cm

1357.98 ml

Clicker Q: How many sig figs?

2. Zeroes are sometimes significant.

0 at beg. of # to position decimal pt never sig

0.123 mg

0.0001598 g

0.015 g Clicker Q: # of sig figs?


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0 between nonzero digits are always sig.

102 g

2.08 milesClicker Q: # of sig figs?

0 at end of # that contains a dec pt are always sig

1.20 g

60.000 g

0 at end of # that doesnt contain a dec. pt may or

may not be sig

24,500 m ?

3 E # i li i d # f i fi (


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3. Exact # contains an unlimited # of sig fig (e.g.

12 eggs, or 1 yard = 3 feet)

A dozen eggs is how many?Clicker Q: 1 m is how many cm?

Clicker Q: 1 ft is how many inches?


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Significant Figures

Examples:


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1. Find the last digit that is to be kept.

2. Check the number immediately to the right:

If that number is less than 5 leave the last digit

alone.If that number is 5 or greater increase the

previous digit by one.

Examples:

Clicker Q: Round this number to 3 sig figs

Rounding Numbers


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Multiplication/Division

The number of significant figures in the answer is

limited by the factor with the smallest numberof

significant figures.

Sig. Figures in Calculations


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45

Multiplication & Division rule

Easier of the two rules.

Product has the smallest number of

significant figures of multipliers

5.22tooffround

21766.5

31.2x

224.4

3.9tooffround

89648.3

41.x

2783.2

A calculated number can NEVER be more

precise than the numbers used to calculate it.


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1.25 cm by 0.25 cm by 10. mm - volume in cm3

Clicker Q: A box is 2.5 cm by 1.54 cm by 1.233 cm.

What is the volume in cm3?

Addition/Subtraction


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Addition/Subtraction

The number of significant figures in the answer is

limited by the least precise number(the numberwith its last digit at the highest place value).

NOTE: counted numbers like 10 dimes never limit

calculations.

6.95tooffround

9463.6

20.2

423.1

3692.3

6.671tooffround

6707.6

312.2

7793.8

20 4


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20.4

1.322

83104.722

12.4 + 1.78 - 10.008


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Combined Operations:When there are both

addition & subtraction and or multiplication &

division operations, the correct number of sfmust

be determined by examination of each step.

(26.05 + 32.1) (0.0032 + 7.7) = ???

Sig. Figures in Calculations

Clicker Q: 81 262 4 47 + 1 3 x 102


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Clicker Q: 81.2624.47 + 1.3 x 102

3.67

How many sig figs will answer have?


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4 Problem Solving by Dimensional Analysis

Dimensional Analysis:

Dimensional analysis converts one unit toanother by using conversion factors (CFs).

The resulting quantity is equivalent to the

original quantity, it differs only by the units.

Examples:


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Examples:

Clicker Q: convert 19.3 g/cm3to kg/ml


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5 Graphs and Graphing

Straight line equation: y = mx + b

m = slope = rise/ run

b = y-intercept, value of y where x =0


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Fig. R-11, p. 41

bl l i d


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6 Problem Solving andChemical Arithmetic Before starting a

problem, devise aStrategy Map.

Use this to collect theinformation given to

work your way throughthe problem.

Solve the problem usingDimensional Analysis.

Check to see that youhave the correct unitsalong the way.


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p. 31

6 materials with

different densities. The

liquid layers are gasoline

(top), water (middle),

mercury (bottom). A

cork floats on gasoline.A piece of oak wood

sinks in gasoline but

floats on water. Brasssinks in water but floats

on mercury.


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p. 33

What are these liquids?

Cli k Q K i h d i / l


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Clicker Q: Knowing that density = mass/volume

Calculate the density of a substance that has a

mass of 12.5 g and occupies a volume of 150. ml.Calculate density in g/ml. Enter just the number

into the clicker.


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What volume in ml would 0.851 grams of air

occupy if the density is 1.29 g/L?

The water level in a graduated cylinder stands at


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The water level in a graduated cylinder stands at

20.0 ml before and at 26.2 ml after a 16.74 g

metal bolt is submerged in the water.

Clicker Q: What is the volume of the bolt?

What is the density of the bolt?

chemistry ch 1.pptx

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