Vector introduction

8/10/2019 Vector introduction

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1. Chemistry: A Science for the 21st

Century2. Measurement

3. Scientific notation

4. Accuracy & Precision


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Chemistry defined as the science that

deal with the materials of the universe

and the changes that these materialsundergo.

Central science most of the

phenomena involve chemical change,where one/more substances become

different substance.


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Health and Medicine

Sanitation systems

Surgery with anesthesia

Vaccines and antibioticsGene therapy - biochemistry

Energy and the Environment

Fossil fuels

Solar energy

Nuclear energy


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Materials industry

Polymers (synthetic/natural)

superconductors electronic devices

catalyst

Food and Agriculture industry

Genetically modified organism(GMO)

pesticides

fertilizers


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Macroscopic Microscopic


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An extensive propertyof a material depends upon how

much matter is is being considered.

An intensive propertyof a material does notdepend

upon how much matter is being considered.

mass

length

volume

density

temperature

color

Extensive and Intensive Properties


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Different instruments enable us to measure a substances

properties. The meter stick measures length or scale; the burette, the

pipette, the graduated cylinder and the volumetric flaskmeasure volume, the thermometer measures temperatures.

These instruments provide measurements of macroscopicproperties, which can be determined directly.

A measured quantity is usually written as a number with anappropriate unit.

UNITS ARE ESSENTIAL TO STATING

MEASUREMENTS CORRECTLY


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The General Conference of Weights and Measures, theinternational authority on units, proposed a revised metricsystem called the International System of Units (SI, from the

French Systeme Internationale dUnites).

Measurements that we will utilize frequently in our study ofchemistry include time, mass, volume, density andtemperature.


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The terms mass and weight are often usedinterchangeably, although they are different quantities.

Massis a measure of the amount of matter in an object.

Weight is the force that gravity exerts on an object. An apple that falls from a tree is pulled downward by Earthsgravity.

The mass of an apple is constant and does not depend on its location,but its weight does.

The SI unit of mass is the kilogram (kg).

1 kg = 1000 g = 1 x 103g


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The SI unit of length is the meter (m), and the SI-derived unitfor volume is the cubic meter (m3).

However, chemists work with such smaller volumes, such as

the cubic centimeter and the cubic decimeter:

Another common unit of volume is the liter (L).

1 cm3= (1 x 10-2m)3= 1 x 10-6m3

1 dm3= (1 x 10-1m)3= 1 x 10-3m3

1 L = 1000 mL = 1000 cm3= 1 dm3

1 mL = 1 cm3


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Density defined in a qualitative manner as the

measure of the relative "heaviness" of objects with a

constant volume.

density =mass

volumed=

m

V

DensitySI derived unit for density is kg/m3

1 g/cm3= 1 g/mL = 1000 kg/m3


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A piece of platinum metal with adensity of 21.5 g/cm3has a volume of4.49 cm3. What is its mass?

d= mV

m= dx V

= 21.5 g/cm3x 4.49 cm3= 96.5 g


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K = 0C + 273.15

273 K = 0 0C373 K = 100 0C

0F = x 0C + 3295

32 0F = 0 0C212 0F = 100 0C

Three temperature scales are currently in use.Their units are 0F (degrees Fahrenheit), 0C (degrees Celcius), and K (kelvin).


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Scientific notation is a way of writingnumbers that are too big or too small to be

conveniently written in decimal form.


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The number of atoms in 12 g of carbon:

602,200,000,000,000,000,000,0006.022 x 1023

The mass of a single carbon atom in grams:

0.00000000000000000000001991.99 x 10-23

N x 10n

N is a numberbetween 1 and 10

nis a positive ornegative integer


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568.762

n > 0

568.762 = 5.68762 x 102

move decimal left

0.00000772

n < 0

0.00000772 = 7.72 x 10-6

move decimal right

Addition or Subtraction

1. Write each quantity with thesame exponent n

2. Combine N1

and N2

3. The exponent, n, remains the

same

4.31 x 104+ 3.9 x 103=

4.31 x 104+ 0.39 x 104= 4.70 x 104


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Multiplication

1. Multiply N1and N22. Add exponents n1and n

2

(4.0 x 10-5) x (7.0 x 103) =(4.0 x 7.0) x (10-5+3) =

28 x 10-2=2.8 x 10-1

Division

1. Divide N1and N22. Subtract exponents n

1and n

2

8.5 x 1045.0 x 109=(8.5 5.0) x 104-9=

1.7 x 10-5


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Any digit that is not zero is significant

1.234 kg 4significant figures

Zeros between nonzero digits are significant

606 m 3significant figuresZeros to the left of the first nonzero digit are not significant

0.08 L 1significant figure

If a number is greater than 1, then all zeros to the right of the decimalpoint are significant

2.0 mg 2significant figures

If a number is less than 1, then only the zeros that are at the end and inthe middle of the number are significant

0.00420 g 3significant figures


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How many significant figures are in each of thefollowing measurements?

24 mL 2 significant figures

3001 g 4 significant figures

0.0320 m3 3 significant figures

6.4 x 104molecules 2 significant figures

560 kg 2 significant figures


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Addition or Subtraction

The answer cannot have more digits to the right of the decimalpoint than any of the original numbers.

89.3321.1+

90.432 round off to 90.4

one significant figure after decimal point

3.70-2.9133

0.7867

two significant figures after decimal point

round off to 0.79


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Multiplication or Division

The number of significant figures in the result is set by the original number that

has the smallestnumber of significant figures

4.51 x 3.6666 = 16.536366 = 16.5

3 sig figs round to3 sig figs

6.8 112.04 = 0.0606926

2 sig figs round to2 sig figs

= 0.061


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Exact Numbers

Numbers from definitions or numbers of objects are considered

to have an infinite number of significant figures

The average of three measured lengths; 6.64, 6.68 and 6.70?

6.64 + 6.68 + 6.70

3= 6.67333 = 6.67

Because 3 is an exact number

= 7


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Accuracyhow close a measurement is to the truevalue

Precisionhow close a set of measurements are to each other

accurate&

precise

precisebut

notaccurate

notaccurate&

notprecise


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