CHEMISTRY AND YOU

 

1.         CHEMISTRY IS THE STUDY OF ALL SUBSTANCES AND THE CHANGES THAT THEY CAN UNDERGO.

 

2.         CHEMISTRY IS A BROAD SCIENCE THAT TOUCHES NEARLY EVERY ASPECT OF LIFE.  SOME OF THE POSSIBLE EXAMPLES MIGHT BE AS FOLLOWS:

 

                        ECOLOGY                 HAIRSTYLIST                        PILOTS

                        MEDICINE                 BIOLOGIST                            PHOTOGRAPHER

                        ENGINEER                 FIREFIGHTER                        MORTICIAN

                        PHARMACY              LAW ENFORCEMENT         MINING

 

3.         CHEMISTRY HAS BEEN CALLED THE CENTRAL SCIENCE BECAUSE IT OVERLAPS SO MANY OTHER SCIENCES.

 

4.         CHEMISTRY CAN BE FUN, IT CAN HELP YOU BETTER UNDERSTAND YOUR WORLD.  BUT MOST IMPORTANT, IT CAN OPEN UP YOUR FUTURE, BECAUSE IT IS SUCH AN IMPORTANT PART OF SO MANY CAREERS.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

UNITS OF MEASUREMENT

 

1.         INTERNATIONSL UNIT SYSTEMS ABBREVIATED SI USES 7 BASIC METRIC UNITS BASED ON INTERNATIONAL STANDARDS.  REFER TO PAGE 18 AND 19.  THIS SYSTEM IS USED IN SCIENCE AND WILL BE USED THROUGHOUT THIS COURSE.  YOU MUST MASTER THIS SYSTEM TO BE SUCCESSFUL IN THIS COURSE.

 

2.         LETS BEGIN:

            THE METER IS THE BASIC UNIT OF LENGTH AND IS ABOUT 1 YARD LONG.

            THE CENTIMETER IS THE UNIT ON THE METER STICK THAT IS ABOUT THE WIDTH OF A SMALL FINGER.

            THE MILLIMETER IS THE SMALLEST UNIT ON THE METER STICK THAT IS ABOUT THE WIDTH OF A FINGERNAIL.

 

3.         YOU MUST MEMORIZE THESE PREFIXES TO BE ABLE TO MANIPULATE THIS SYSTEM.  THEY ARE ALL BASED ON ONE CENTRAL UNIT.  FOR LENGTH THAT UNIT IS A METER, FOR WEIGHT OR MASS IT IS A GRAM, AND FOR VOLUME IT IS A LITER.

 

            MEGA             M         =          1,000,00          METER-GRAM-LITER = 1

            KILO               K         =          1,000               DECI d                            = .1

            HECTO           H         =          100                  CENTI c                          = .001

            DEKA             D         =          10                    MILLI m                          = .001

            METER-GRAM-LITER =        1                     MICRO u                        = .000 01   10-6

                                                                                    NANO n                         = .000 000 001  10-9

                                                                                                                PICO p                    = .000 000 000 001 10-12

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BASIC UNITS

 

SI consists of seven basic units. (figure 1)  All other SI units are derived from these seven.

 

Quantity Measured

Unit Name

SI Symbol

Length

Meter

m

Mass

Kilogram

kg

Time

Second

s

Electric Current

Ampere

A

Temperature

Kelvin

K

Amount of substance

Mole

mol

Luminous

Candela

cd

Figure 1. SI base units.

 

 

A prefix system representing various powers of 10 has been defined in SI.  Each base unit can be

enlarged or reduced to a convenient size.  Figure 2 lists some commonly used prefixes.

 

Prefix

Symbol

Basic Unit Amount

Exponential Notation

mega

M

1 000 000

106

kilo

k

      1000

103

centi

c

           0.01

10-2

milli

m

              0.001

10-3

micro

u

                  0.000 001

10-6

nano

n

                      0.000 000 001

10-9

pico

p

                          0.000 000 000 001

10-12

Figure 2.  Prefixes for fractions and multiples of SI units.

 

For example, the distance between two towns is better expressed as 9.5 km rather than 9500 m.

The distance between hydrogen and oxygen nuclei in a water molecule is about

0.000 000 000 097 m.  Obviously this distance is better expressed as 0.097 nm or 97 pm.  Indeed,

atomic dimensions are of the order of a fraction of a nanometer or 10s of picometers.  Thus, the

unit chosen is the one most appropriate for the magnitude of the measurement.

 

 

 

 

 

 

 

 

 

 

 

 

DERIVED SI UNITS

 

Quantity

Unit Name

Symbol

SI

Derivation

Non – SI

Unit

SI equivalent

 

 

 

m s-2

 

 

Area

 

 

m2

 

 

Celsius temperature

 

 

 

Degree

Celsius (oC)

0 oC = 273.15 K

Density

 

 

kg m-3

g L-1

1 g L-1 = 1 kg m-3

Electric charge

Coulomb

C

A s

 

 

Energy potential

Volt

V

J C-1

 

 

Energy

Joule

J

N m

Calorie (cal)

1 cal = 4.184 J

Force

Newton

N

kg m s-2

Dyne

1 dyne = 10-5 N

Frequency

Hertz

Hz

s-1

 

 

Molar volume

 

Vm

M3 mol-1

L mol-1

1 L mol-1 = 10-3m3mol-1

Power

Watt

W

J s-1

 

 

Pressure

Pascal

Pa

N m-2

Atmosphere

1 atm=760 torr=760 mm Hg = 101325 Pa

Volume

 

 

M3

Liter (L)

1 L = 10-2m3 = 1 dm3

Figure 3.  Derived SI and commonly used equivalent units

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

METRIC CONVERSATION AND

USING WHAT WE KNOW

 

→  Since you know the meaning of many of the prefixes already, you can use that knowledge to memorize how they relate to the central units of meter, grams, or liters.  For example you have seen deka and deci in decade which is ten years.  You have seen centi in century which you know is 100 years and you have seen milli in millennium which you know is 1000 years.  Using this knowledge to build on, you can create conversion factors which you can use to convert from one metric unit to another.  The conversion factors are as follows:

 

→  (base units are meters for length, grams for mass, liters for volume, or any unit such as joules, amps, calories, ohms etc.

 

 

METRIC CONVERSION FACTORS

 


      1 mega             =      1,000,000 base

 


        1 kilo                =      1,000 base units

 


        1 hecto            =      100 base units

 


        1 deka              =      10 base units

 


        base unit          =      1

 


        1 base unit       =      10 deci

 


        1 base unit       =      100 centi

 


        1 base unit       =      1000 milli

 


        1 base unit       =      1,000,000 micro

 


        1 base unit       =      1,000,000,000 nano

 


        1 base unit       =      1000,000,000,000 pico

 

 

 

 

 

 

 

 

 

 

 

USING THE CONVERSION FACTORS

 


        ONCE YOU KNOW THE CONVERSION FACTORS FOR EACH PREFIX YOU CAN USE THEM TO CONVERT FROM ONE METRIC UNIT TO ANOTHER JUST AS YOU WOULD ANY OTHER CONVERSION PROBLEM BY USING DIMENSIONAL ANALYSIS.

 


        EXAMPLE:       How many milligrams are in 5 kilograms?

 


5 kilograms  x   1000 grams/1 kilogram x 1000 milligrams/1 gram =

 


5 k  x  1000 g  x  1000 mm / 1k x 1g = 5,000,000 millimeters

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SCIENTIFIC NOTATION

 

1.         THIS IS USED TO MAKE MATHEMATIC CALCULATIONS EASIER WHEN WORKING WITH VERY LARGE OR SMALL NUMBERS.

 

2.         FOR EXAMPLE IF YOU ARE ASKED TO MULTIPLY 5,200,000,000, IT IS MUCH EASIER TO WORK WITH THIS NUMBER IN SCIENTIFIC NOTATION

            5.2 X 10.

 

3.         IN SCIENTIFIC NOTATION THE FIRST NUMBER (5.2) ARE THE SIGNIFICANT DIGITS IN A NUABER AND THE POWER OF 10 (10) TAKES CARE OF THE ZERO DIGITS.

 

            EXPLANATION – IF YOU WERE TO COVERT 1,000 AND .001 TO SCIENTIFIC NOTATION, CONSIDER THE FOLLOWING:

 

                                    1,000 = 10 x 10 x 10 = 103

                                    .001   =  1/10 x 1/10 x 1/10 = 1/10 = 10-3

 

4.         INSTEAD OF MULTIPHYING OUT THE NUMBER EACH TIME YOU CAN COUNT THE ZEROS AND PLACE AS POWERS OF 10.

 

5.         EXAMPLES:

 

                        A.        1,000 = 3 ZEROS = 103

 

                        B.         5,200,000,000,000 = 5.2 x 1012

                                                                        DECIMAL POINT ALWAYS GOES

                                                                        BETWEEN THE FIRST TWO DIGITS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IF YOU HAVE A HARD TIME DECIDING IF IT SHOULD BE 10 OR 10,

ABOUT IT THIS WAY.  IN EXAMPLE B YOU MADE THE NUMBER SMALLER BY 12

ZEROS.  TO KEEP YOUR NEW NUMBER EQUAL TO THE ORIGINAL NUMBER YOU

HAVE TO MULTIPLY BY 10, 12 TIMES.

 

            C.        .00256 = 2.56 x 10-3

 

SINCE THE NEW NUMBER WAS MADE LARGER, TO KEEP THE NEW NUMBER

EQUAL TO THE ORIGINAL NUAMBER, IT HAS TO BE REDUCED BY 10, 3 TIMES.

 

 

PERCENT ERROR

 

 

                        PERCENT ERROR                             MEASURED VALUE – ACTUAL

                                    100                              =          ACTUAL VALUE

 

            THIS CAN BE POSITIVE OR NEGATIVE

 

1.         EXAMPLE:  IN MEASURING THE VOLUME OF AN OBJECT, IT FOUND TO BE 10 ML.  ITS ACTUAL VOLUME WAS 9 ML.  HOW MUCH ERROR WAS THE MEASUREMENT?

 

                                    PERCENT ERROR                 10ML – 9ML

                                                100                      =               9ML

 

                        PERCENT ERROR =   1 ML/9ML x 100 = 11%

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RATIOS

 

1.         RATIOS PLAY AN IMPORTANT ROLE IN SCIENCE BECAUSE A FATIO RELATES VARIABLES TO EACH OTHER.

 

2.         DENSITY IS A GOOD EXAMPLE OF A RATIO.  IT RELATES MASS TO VOLUME.

 

                                    DENSITY = MASS

                                                VOLUME

 

3.         EXAMPLE:  IF 10 GRAMS OF SUBSTANCE WAS FOUND IN 20ML, WHAT IS THE DENSITY OF THE SUBSTANCE?

 

                                    DENSITY = 10GM/20ML = .5GMS/ML

 

4.         THE PROBLEM COMES IN, IF DENSITY IS GIVEN AND THE PROBLEM ASKS FOR MASS OR VOLUME.  FOR EXAMPLE:  IF A SUBSTANCE HAS A DENSITY OF 10GM/ML AND A VOLUME OF 20ML, WHAT IS ITS MASS?  THIS REQUIRES A BASIC KNOWLEDGE OF ALGEBRA.  IF THIS IS A PROBLEM, YOU NEED EXTRA HELP.  GET WHAT EVER YOU NEED, DON’T GO ANY FURTHER WITHOUT IT.

 

                        1.         D = M/V

                       

                        2.         10GM/ML = M/20ML

 

                        3.         20ML/1 x 10GM/ML = M/20ML x 20ML

 

                        4.         200GM = M

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ALGEBRA REVIEW

 

1.         GIVEN D = M/V.  IN FINDING ANY UNKNOW, IT MUST BE BY ITSELF.  TO DO THIS, ANYTHING CAN BE DONE ALONG AS IT IS DONE ON BOTH SIDES TO KEEP BOTH SIDES EQUAL AS THE EQUAL SIGN INDICATES.

 

2.         IF A VARIABLE IS BEING MOVED FROM ONE SIDE TO THE OTHER JUST DO THE OPPOSITE OF WHAT IS BEING DONE IN THE EQUATION.  THIS MAKES THE VARIABLE 1 AND ELIMINATES IT.  FOR EXAMPLE:

 

                        A.        SOLVING FOR V IN D = M/V

                                                D = M/V x 1/M (OPPOSITE)  M/1 x 1/M = M/M = 1

                                                D/M = 1/V MUST INVERT M/D = V/1 OR V

 

                        B.         SOLVING FROM M

                                                D = M/V x V/1 (OPPOSITE) 1/V x V/1 = V/V = 1

 

            IF THE NUMBER IS ADDED OR SUBTRACTED IN AN EQUATION, THE OPPOSITE IS DONE TO MOVE IT.  FOR EXAMPLE:

                        IN A = B – 2, IF B IS BEING SOLVED FOR A + 2 IS ADDED.

            ALTHOUGH IT WASN’T INDICATED IN THE EXAMPLES DON’T FORGET THAT THE SAME THING HAS TO BE DONE ON THE OPPOSITE OF THE EQUATION TO KEEP IT EQUAL.

 

            IN A FRACTION A/B, THE B IS ALWAYS DIVIDED INTO A.  IF THIS HAS NOT BEEN LEARNED BY KOW, DON’T EVER FORGET IT AGAIN.  THIS IS VERY SIMPLE BUT BY NOT KNOWING IT IS AN IMPOSSIBLE STUMBLING BLOCK.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CONVERSION OF UNIT FROM ENGLISH UNITS TO METRIC OR VICE VERSA

 

1.         YOU NEED TO USE DIMENSIONAL ANALYSIS.  FOR EXAMPLE IF A PROBLEM ASKS HOW MANY LITERS ARE IN 250 GALS. OF WATER, DO THE FOLLOWING:

 

A.        START WITH A UNIT EQUATION.  USING THE EQUATION CHART ON PAGE 38.  FIND 1 GAL = 3.785 L.

 

            MAKE THIS INTO A CONVERSION FACTOR BY MAKING EACH SIDE INTO ONE.  THIS IS DONE BY DIVIDING BY THE UNIT ITSELF.

 

                                    1GAL/1GAL = 3.785L/1GAL

 

                        THE REVERSE FACTOR IS DONE THE SAME WAY

                                   

                                    1GAL/3.785L = 3.785L/3.78L = 1L

 

B.         IN USING THE CONVERSION FACTORS. IT MAY NOT BE OBVIOUS WHICH FACTOR TO USE.  IF THIS HAPPENS, USE BOTH FACTORS AND DECIDE WHICH FACTOR GIVES THE CORRECT UNIT NEEDED.

 

            THIS PROBLEM IS LOOKING FOR LITERS

           

                                    250GAL x 1GAL/3.785 LITERS = 66.05GAL /LITERS

                        THIS IS NOT A CORRECT UNIT.

 

                                    250 GAL x 3.785l/1GAL = 946.25LITERS

                        THIS GIVES THE PROPER UNIT.  IF THIS IS CONFUSING, THERE IS A MATH PROBLEM.  IF CLASS DOESN’T HELP, GET EXTRA HELP BEFORE GOING ON.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

GRAPHING

 

1.         GRAPHING GIVES A BETTER PICTURE OF THE RELATIONSHIP OF TWO VARIABLES THAN JUST HAVING THEM IN A DATA CHART.  THERE ARE TWO VARIABLES INVOLVED IN AN EXPERIMENT.  ONE FARIABLE IS THE RESULTS.  THIS IS CALLED THE DEPENDENT VARIABLE BECAUSE IT IS DEPENDENT ON THE EXPERIMENT AND OUT OF THE SCIENTISTS CONTROL.  THIS VARIABLE IS PLACED ON THE Y AXIS OF A GRAPH.  THE VARIABLE BEING TESTED IS CALLED THE INDEPENDENT VARIABLE.  BECAUSE THE SCIENTIST CONTROLS IT MAKING IT INDEPENDENT.  THE VARIABLE GOES ON THE X AXIS OF A GRAPH.

 

2.         EXAMPLE:  WHAT WOULD HAPPEN TO THE VOLUME OF AIR IN A BALLOON IF IT IS HEATED IN AN              

 


            Trial     Temp   Vol

            1          25        101.3               110

            2          30        102.4               108

            3          35        103.4               106

            4          40        105.2               104

            5          45        106.7               102

            6          50        108.4               100                                                                     .

            7          55        110.0                         20          30        40        50        60        70

                                   

 

THE SCIENTIST IS CONTROLLING THE TEMP FRATURE MAKING IT THE INDEPENDENT VARIABLE AND WOULD BE PLACED ON THE X AXIS.  THE VOLUME IS THE RESULTSOF THE TEMPERATURE CHANGE.  IT IS THE DEPENDENT VARIABLE AND IS PLACED ON THE Y AXIS.

 

NOTICE THE GRAPH SHOWS A BETTER PICTURE TO ANALYZE THAN THE DATA CHART.

            TO INTERPOLATE YOU INTERPET INFORMATION WITHIN THE GRAPH THAT DOES NOT FALL ON SPECIFIC DATA TO EXTRAPOLATE YOU INTERPET INFORMATION BEYOND YOUR DATA.

 

 

 

 

 

 

 

 

 

 

UNCERTAINTY IN MEASUREMENTS

 

1.         IN MAKING MEASUREMENTS YOU SHOULD ALWAYS ESTIMATE ONE PLACE PAST WHAT CAN BE ACTUALLY MEASURED.  FOR EXAMPLE, IF YOUR METER STICK MEASURES TO MILLIMETERS, YOU SHOULD ESTIMATE TO10THS OF A MILLIMETER.  IF AN OBJECT IS MEASURED TO BE SLIGHTLY LARGER THAN 10 MILLIMETERS YOU MIGHT ESTIMATE IT TO BE 10.2 MILLIMETERS.

 

2.         BECAUSE THE LAST DIGIT IS EXTIMATED, IT HAS AN UNCERTAINTY OF AT LEAST .1 MILLIMETERS.  THEREFORE, THE MEASUREMENT WOULD BE WRITTEN 10.2 MILLIMETERS.

 

            RELIABILITY HAS TWO WAYS TO BE CHECKED – PERCISION AND ACCURACY.  PERCISION MEANS YOUR MEASUREMENT IS CONSISTENT, IT DOESN’T MEAN IT IS ACCURATE.  IF YOU MEASURE WITH AN INACCURATE INSTRUMENT, YOU CAN BE CONSISTENT (PRECISE) BUT CONSISTENTLY WRONG.  ACCURACY MEANS YOUR MEASUREMENTS ARE THE SAME AS THE STANDARD SET FOR THEM.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SIGNIFICANT FIGURES

 

1.         THE CERTAIN DIGITS AND THE ESTIMATED DIGIT OF A MEASUREMENT ARE TOGETHER CALLED THE SIGNIFICANT DIGITS OF THE MEASUREMENT.

 

2.         THIS BECOMES TRICKY BECAUSE ZEROS CAN BE PLACED HOLDERS AND NOT SIGNIFICANT.  FOR EXAMPLE,  IF A MEASUREMENT CAN BE MEASURED TO THE 100THS PLACE, YOU ESTIMATE THE TENTHS PLACE.  THE 0 IN THE UNITS PLACE WOULD JUST BE A PLACEHOLDER.  IF THE NUMBER WERE 1140, THERE WOULD BE 3 SITGNIFICANT FIGURES.  THE 1 IN THE HUNDREDTHS PLACE WAS MEASURED.  THE FOUR WAS ESTIMATED IN THE TENTHS PLACE, BUT THE ZERO IS NOT SIGNIFICANT IT IS JUST A PLACE HOLDER FOR THE NUMBER.

 

3.         THERE IS A RULE THAT CAN HELP DETERMINE SUGNIFICANT NUMBERS.  THIS IS CALLED THE ATLANTIC-PACIFIC RULE.  IF THE NUMBER HAS A DECIMAL COUNT FROM THE PACIFIC SIDE STARTING WITH THE FIRST NONZERO DIGIT.  IF THERE IS NOT A DECIMAL START FROM THE ATLANTIC SIDE WITH THE FIRST NONZERO NUMBER.

 

4.         EXAMPLE:

 

                        PACIFIC         .0093077         5 SIGNIFICANT

.0093077         7 SIGNIFICANT (LINE USED TO SHOW SIGNIFICANT)

2.0093077       8 SIGNIFICANT

2.0093077       9 SIGNIFICANT 0 IS NOT A PLACE HOLDER SO SIG

                        ATLANTIC     2009300000    5 SIGNIFICANT

2009300000    7 SIGNIFICANT (LINE USED TO SHOW SIGNIFICANT)

            NOTICE ALL ZEROS BETWEEN NONZERO NUMBERS ARE SIGNIFICANT.

 

5.         WHEN NUMBERS ARE MANIPULATED MATHEMATICALLY, THE ANSWER CAN ONLY BE AS ACCURATE AS THE LEAST ACCURATE NUMBER INVOLVED.

 

 

 

 

 

 

 

 

 

 

6.         EXAMPLE:                 3.05 x 2.10 x 0.75        =          4.89375 = 4.8

            MULTIPLY                 3 SIG    3 SIG    2 SIG                   2 SIG

 

7.         EXAMPLE:     LINE UP THE NUMBERS AND ROUND TO THE LEAST PLACE ADDITION HOLDER.

 

                                                            951.0

                                                           1407

                                                               23.911

                                                             158.18

                                                            2540.

 

8.         EXAMPLE:    WHEN A CALCULATION IS PERFORMED IN STEPS, EXTRA DIGITS ARE CARRIED IN THE INTERMEDIATE STEPS.  ONLY THE FINAL ANSWER IS TO THE PROPER NUMBER OF SIGNIFICANT FIGURES.

 

                                    35.6 + 2.4        38.0 (3 SIG)

                                       4.803       =     4.803             =          7.91 (3 SIG)