unit 1 introduction to chemistry

Unit 1Introduction to Chemistry

Internet web site: www.unit5.org/chemistry

Outline

PowerPoint Presentation by Mr. John Bergmann

Safety

Basic Safety Rules

Use common sense.

No horseplay.No unauthorized experiments. Handle chemicals/glassware with respect.

Others:

#1 Rule:

Safety Features of the Lab

safety showerfire blanketfire extinguishereye washfume hoodcircuit breaker switch

Material Safety Data Sheet (MSDS)

gives informationabout a chemical

-- lists “Dos” and “Don’ts;” emergency procedures

--

Chemical Exposure

a one-time exposure causes damage

acute exposure chronic exposuredamage occurs after repeated exposure

reaction to drugsor medication

e.g., e.g., smoking,asbestos

the lethal dosage for 50% of the animals on which the chemical is tested

LD50

There are various ways an LD50 can be expressed. For example, acetone has the following LD50s:

ORL-RAT LD50: 5,800 mg/kgIHL-RAT LD50: 50,100 mg/m3-hSKN-RBT LD50: 20 g/kg

Example

Which is more toxic?

Chemical A is more toxic because less of it proves fatal to half of a given population.

Chemical A: LD50 = 3.2 mg/kgChemical B: LD50 = 48 mg/kg

Science

The Functions of Sciencepure science applied sciencethe search for

knowledge; factsusing knowledgein a practical way

e.g., aluminum

stronglightweight

good conductor

Science attempts to establish cause-effect relationships.

risk-benefit analysis weigh pros and cons before deciding

Because there are many considerations for each case, “50/50 thinking” rarely

applies.

How does scientific knowledge advance?

1. curiosity2. good observations3. determination4. persistence

The Scientific Method

** Key: Be a good observer.

observation inferenceinvolves a judgment

or assumptionuses the five

senses

Types of DataObservations are also called data.

qualitative data quantitative data

clear liquid --

-- e.g., e.g.,

descriptions

measurements 55 L or 83oC

Parts of the Scientific MethodIdentify an unknown.

Make a hypothesis: a testable prediction

Repeatedly experiment to testhypothesis.

procedure: order of events inexperiment

variable: any factor that couldinfluence the result

(i.e., a recipe)

A ScientificExperiment

conclusion: must be based on the data

Experiments must be controlled:

they must have two set-upsthat differ by only one variable

Scientific Law vs. Scientific Theorylaw:

Theory of Gravity,Atomic Theory

states what happens

tries to explain why orhow something happens

-- e.g.,

does not change

law of gravity,laws of

conservation

never violated--

--

theory:

-- e.g., -- based on current evidence

Phlogiston Theory of Burning1. Flammable materials contain phlogiston.2. During burning, phlogiston is released

into the air.3. Burning stops when… …object is out of phlogiston, or …the surrounding air contains

too much phlogiston.

(superceded by combustion theory of burning)

Chemistry

The Beginning

The Greeks believed therewere four elements.

early practical chemistry:household goods, weapons, soap, wine, basic medicine

earth wind fire waterD ~~D___

D

___

Alchemy

Allegedly, this substance would turn cheap metals into gold.

the quest for the Philosopher’s Stone

(~500 – 1300 C.E.)

(the elixir, the Sorcerer’s Stone)

Alchemical symbols for substances…

. . . . . . . . . . . .. . .

GOLD SILVER COPPER IRON SAND

transmutation:

we cannottransmute elements into different elements.

changing one substanceinto another

COPPER GOLD

Philosopher’sStone

In ordinary chemical reactions…

Alchemy was practiced in many regions of theworld, including China and the Middle East.

Alchemy arrived in western Europe around the year 500 C.E.

Modern chemistry evolved from alchemy.

Contributionsof alchemists:

• experimental techniques• new glassware• information about elements• developed several alloys

What is Chemistry?

the study of matterand its changes

Areas of Chemistryorganic

physicalinorganic

biochemistry

studies everythingexcept carbon

e.g., compoundscontaining metals

the study of carbon-containing

compounds

measuring physicalproperties ofsubstances

the chemistry ofliving things

e.g., the melting point of gold

Careers in Chemistry

• research (new products)• production (quality control)• development (manufacturing)• chemical sales• software engineering• teaching

The skills you will develop by an earneststudy of chemistry will help you in any

career field.

The Scope of Chemistry

pharmaceuticals

nylon, polyester, rayon

bulk chemical manufacturing

petroleum products

synthetic fibers

acids, bases, fertilizers

fuels, oils, greases, asphalt

1 in 10,000 new products gets FDA approval

spandex,

**sulfuric acid (H2SO4) = #1 chemical

All fields of endeavor are affected by chemistry.

Government Regulation of Chemicals

The governmentregulates chemicals

to protect the…OSHAworker

FDAUSDAFAA

CPSC consumer

EPAenvironment

Manipulating Numerical Data

Graphs

Bar Graphshows how many of something

are in each category

0

2

4

6

8

10

A B C D F

Chemistry Grades

# of

stu

dent

s

Pie Graph shows how a whole is broken into parts

Entertainment (40%) Food (25%)Clothing (20%)Savings (15%)

Percentage ofWeekly Income

Line Graphshows continuous change

0

10

20

30

40

50

60

Jan Feb Mar Apr

Month

Shar

e Pr

ice

($)

Stock Price over Time

you will always use a line graph. In chemistry…

Elements of a “good” line graph

2. axes labeled, with units

Temp. v. Vol. for a Gas at Constant Pressure

0123456789

10

120 140 160 180 200 220 240

Temp. (K)

Volu

me

(L)

4. use the available space

1. title

3. neat

Essential Math of Chemistry

Scientific Notation-- used to express very large or very small

numbers, and/or to indicate precision(i.e., to maintain the correct number

of significant figures)Form: (# from 1 to 9.999) x 10exponent

800 = 8 x 10 x 10 = 8 x 102

2531 = 2.531 x 10 x 10 x 10 = 2.531 x 103

0.0014 = 1.4 10 10 10 = 1.4 x 10–3

Put in standard form. 1.87 x 10–5 = 0.0000187

3.7 x 108 = 370,000,000 7.88 x 101 = 78.8 2.164 x 10–2 = 0.02164

Change to scientific notation. 12,340 = 1.234 x 104

0.369 = 3.69 x 10–1

0.008 = 8 x 10–3 1,000,000,000 = 1 x 109

6.02 x 1023 = 602,000,000,000,000,000,000,000

Using the Exponent Key

EXP

EE

The EE or EXP or E key means “times 10 to the…”

How to type out 6.02 x 1023:

6 EE. 0 32 2

6 y x. 0 32 2

x 16 . 0 2 EE 320

y x 32x 16 . 0 2 0

not…

or…

and not…

How to type out 6.02 x 1023:

6 EE. 0 32 2

WRONG!

WRONG!

TOO MUCH WORK.

Also, know when to hit your (–) sign.

(before the number, after the number, or either one)

4.3 x 10–9 4.3 E –9or

1.2 x 105 2.8 x 1019

But instead is written…

=

1 . 2 EE 5

92 . 8 EE 1

Type this calculation in like this:

This is NOT written… 4.3–15

4.2857143 –15Calculator gives…

4.2857143 E–15or…

–6.5 x 10–19

5.35 x 103 or 5350

2.9 x 1023

7.5 x 10–6 (–8.7 x 10–14) =

4.35 x 106 (1.23 x 10–3) =

5.76 x 10–16 9.86 x 10–4 =

8.8 x 1011 x 3.3 x 1011 =

5.84 x 10–13

Essential Mathof Chemistry

Units must be carried into the answer, unless they cancel.

0.64 kg-ms2

5.2 kg (2.9 m) (18 s)(1.3 s)

=

4.8 kg (23 s) (18 s)(37 s)

= 0.57 kgs

Solve for x. x + y = z

x + y = z – y – y

x = z – y

x and y are connected by addition. Separate them using subtraction. In general, use opposing functions to separate things.

The +y and –y cancel on the left,

leaving us with…

Solve for x. x – 24 = 13

x – 24 = 13 +24 +24

x = 37

x and 24 are connected by subtraction. Separate them using the opposite function: addition.

The –24 and +24 cancel on the left,

leaving us with…

Numerical Example

Solve for x. F = k x

F = k xk k

x = Fk __

x and k are connected by multiplication. Separate them using the opposite function: division.

( )__1kF = k x( )__1

k

(or)

The two k’s cancel on the right,

leaving us with…

Numerical ExampleSolve for x. 8 = 7 x

8 = 7 x7 7

x and 7 are connected by multiplication. Separate them using the opposite function: division.

( )__178 = 7 x( )__1

7

(or)

The two 7’s cancel on the right,

leaving us with…x = 87

__

Solve for x. ___ x

BA = TRH

___

BAH = xTR

One way to solve this is to cross-multiply. BAH = xTR

Then, divide both sides by TR.

The answer is… ___BAHTR

x =

1TR( )___1

TR( )___

Solve for T2, where…P1 = 1.08 atmP2 = 0.86 atmV1 = 3.22 LV2 = 1.43 LT1 = 373 K

P1V1T2 = P2V2T1

____ T1

P1V1 = P2V2

T2

____

1P1V1

( )____ 1P1V1

( )____

T2 = P1V1

______P2V2T1

132T2 = (1.08 atm)(3.22 L)_____________________(0.86 atm)(1.43 L)(373 K)

= K

SI Prefixes

kilo- (k) 1000deci- (d) 1/10

centi- (c) 1/100

milli- (m) 1/1000

Also,1 mL = 1 cm3 and 1 L = 1

dm3

Conversion Factorsand

Unit Cancellation

How many cm are in 1.32 meters?

conversion factors:

equality:

or

1.32 m = 132 cm

1 m = 100 cm

______1 m100 cm

We use the idea of unit cancellationto decide upon which one of the two

conversion factors we choose.

______1 m

100 cm

( )______1 m

100 cm

(or 0.01 m = 1 cm)

How many m is 8.72 cm?

conversion factors:

equality:

or

8.72 cm = 0.0872 m

1 m = 100 cm

______1 m100 cm

Again, the units must cancel.

______1 m

100 cm

( )______1 m100 cm

How many kilometers is 15,000 decimeters?

15,000 dm = 1.5 km( )____1,000 m

1 km10 dm

1 m ( )______

How many seconds is 4.38 days?

= 378,432 s1 h

60 min24 h1 d 1 min

60 s____( ) ( )____( )_____4.38 d

3.78 x 105 sIf we are accounting for significant figures, we would change this to…

Simple Mathwith

Conversion Factors

Find area of rectangle.

A = L . W

= (4.6 cm)(9.1 cm)

9.1 cm= 42 cm2 . cm

4.6 cm

Convert to m2. 42 cm2 ( )______100 cm

1 m 2 = 0.0042 m2

Convert to mm2. 42 cm2 ( )______ 1 cm10 mm 2 = 4200 mm2

cm.cm

For the rectangular solid:

Find volume.

Length = 14.2 cm Width = 8.6 cm Height = 21.5 cm

V = L . W . H

= (14.2 cm)(8.6 cm)(21.5 cm)

= 2600 cm3

Convert to mm3.

2600 cm3 ( )______ 1 cm10 mm 3 = 2,600,000 mm3

= 2.6 x 106 mm3

mm and cm differ by a factor of……….

mm2 “ cm2 “ “ “ “ “ ……….

mm3 “ cm3 “ “ “ “ “ ……….

10

100

1000

Basic Concepts in Chemistry

chemical: any substance that takes part in, or occurs as a result of,a chemical reaction

All matter can be considered to bechemicals or mixtures of chemicals.

chemical reaction: a rearrangement ofatoms such that…

“what you end up with”

differs from

“what you started with”

products

reactants

methane + oxygen

+ H2O(g)

carbondioxide

O2(g) CO2(g)CH4(g) +

water+

22

NaOH(aq)

water

Na(s) H2O(l) H2(g) 2

sodium

2 2

hydrogen sodiumhydroxide

+ +

+ +

Law of Conservation of Masstotal mass total massof products of reactants

Pmass = Rmass

=

synthesis: taking smallmolecules and puttingthem together, usuallyin many steps, to makesomething more complex JENNY

How many feet is 39.37 inches?

applicable conversion factors:

equality:

or

X ft = 39.37 in =

1 ft = 12 in

______1 ft 12 in

Again, the units must cancel.

( )____ 3.28 ft1 ft12 in

______1 ft

12 in

Lab – introduction to qualitative analysis

Resources - Intro. to ChemistryWorksheet - vocabulary

Worksheet - material safety data sheet (acetone)

Activity - checkbook activity

Worksheet - graphingWorksheet - real life chemistry

Worksheet - conversion factors

Worksheet - scientific notation

Worksheet - metric article (questions)

Worksheet - significant digits

Worksheet - math review

Worksheet - math of chemistry

Outline (general)

Worksheet - article on the metric system Textbook - questions

Episode 1 - The World of Chemistry

Episode 4 - Modeling The Unseen

Episode 3 – Measurement: The Foundation of Chemistry