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C H E M 1 0 0
GENERAL CHEMISTRY
Lecturer: Prof. Dr. Tamerkan Özgen
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Prentice-Hall © 2005
Chapter 1: Chemistry : Matter and Measurement
General ChemistryFouth Edition
Hill • Petrucci • McCreary • Perry
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Contents
1.1 Chemistry: Principles and Applications
1.2 Getting Started: Some key terms
1.3 Scientific measurements
1.4 Precision and Accuracy in Measurements
1.5 A Problem-Solving Method
1.6 Further Remarks on Problem Solving
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1.1 Chemistry: Principles and Applications
In their daily life people have always practiced chemistry
making drugs to fight disease;
computer chips;
pesticides to protect humans, animals and crops;
fertilizers to grow more food;
fibers for clothes;
building materials for housing;
replacing worn out body parts.
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1.1 Chemistry: Principles and Applications
Glazing of pottery;
smelting of ores to produce metals;
tanning of leather;
dyeing of fabrics;
making of cheese, wine, beer and soap,
From petroleum, motor fuels and thousands of chemicals used in the
manufacture of plastics, synthetic fabrics, pharmaceuticals, and pesticides.
From coal thousands of chemicals for various uses
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1.1 Chemistry: Principles and Applications
Modern chemical knowledge is also needed
to understand the processes that control life and
to understand and control processes in the environment,
such as the formation of smog and the destruction of
stratospheric ozone.
Early chemical knowledge consisted of the “how to” of chemistry
Modern chemical knowledge answers the “why” as well as the
“how to” of chemical change.
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1.2 Getting Started. Some Key terms
Chemistry: Study of the composition, structure, and properties
of matter and of changes that occur in matter.
Matter: Occupies space, has mass and inertia
Atoms: The smallest distinctive units in a sample of matter
Molecules: Larger units in which two or more atoms are joined
together
Composition: Types of atoms and relative proportions of diferent
atoms in a sample of matter
ex. H2O, 11.19% H and 88.81% O
Properties: Distinguishing features, ( mainly physical and
chemical properties)
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Properties of Matter
A physical property of matter displays without changing its
composition. Ex: color, brittleness, malleability, ductility.
A chemical property is a characteristic shown by a sample
of matter as it changes in composition.
In a chemical change, or chemical reaction, one or more
kinds of matter are converted to new kinds of matter with
different compositions (change in composition).
Ex. Zn + HCl giving ZnCl2 and H2 ,
Na + H2O giving NaOH and H2
HCOOH (formic acid) decomposing to CO and
H2O
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States of Matter
a) solid b) liquid c) gas
Animations
1: Change of State
2: Physical Properties of Halogens
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Chemical Symbol
A chemical symbol is a one- or two-letter symbol derived from
the name of an element.
Most symbols are based on English names; a few are based on
the latin name of the element. (eg. He, Ba, Na, Hg)
The first letter of a chemical symbol is always capitalized and the
second is never capitilized.
Chemists show compounds by combinations of chemical
symbols called chemical formulas.
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Chemical Symbol
To represent a particular atom we use the symbolism:
A= mass number Z = atomic number
To represent an ion
Symbols
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35 Cl
1727
Al13
56 Fe
26
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Classification of Matter
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Classifying Matter
Figure 1.3
Atoms Molecules
make up
ALL MATTER
which exists as
Substances Mixtures
which may be
Elements Compounds Heterogeneous
which may be
Homogeneous
Animations
3: Mixtures and Compounds
4: Dissolution of NaCl in Water
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The Scientific Method
The ancient Greeks developed methods using knowledge
and mathematics.
They started with certain basic assumptions. Then by
deduction method certain conclusions logically followed.
Ex. if a = b and b = c, then a = c.
Greek philosopher Aristotle assumed four fundamental
substances: air, earth, water and fire. All other
materials, he believed, were formed by the combination of
these four elements. For many years this was accepted.
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The Scientific Method
Scientists often begin by making observations and then formulating a
hypothesis. A hypothesis is an explanation or prediction concerning
some phenomenon.
Scientists test a hypothesis through a carefully controlled procedure
called an experiment.
Scientific data are obtained during experiments.
Further experiments may be carried to refine these data.
Large collections of data may be summerized to identfy patterns which
are called scientific laws.
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The Scientific Method
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1.3 Scientific Measurements
• Scientists worldwide use a common system of measurement,
called Systeme Internationale d’Unites (International System
of Units) which is in short written as SI .
• This system was adopted in 1960, and is
• A modernized version of the metric system established in France
in 1791.
• In modern scientific work, all measured quantities can be
expressed in terms of the seven base units listed in the next slide.
• An essential aspect of SI is the use of exponential (powers of ten)
notation for numbers.
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Units
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Units
Derived Quantities
Force Newton, kg m s-2
Pressure Pascal, kg m-1 s-2
Energy Joule, kg m2 s-2
Other Common Units
Length Angstrom, Å, (10-8 cm)
Volume Litre, L, (10-3 m3)
Energy Calorie, cal, (4.184 J)
Pressure 1 Atm = 101.325 kPa
1 Atm = 760 mm Hg = 760 Torr
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Wrong units
The Gimli Glider
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EDMONTON
• The Gimli Glider is the nickname of an Air Canada aircraft which was
involved in a notable aviation incident.
• On 23 July 1983, Air Canada Flight 143, a Boeing 767-200 jet, ran
completely out of fuel at 41,000 feet (12,500 m) altitude, about halfway
through its flight from Montreal to Edmonton via Ottawa. The crew was
able to glide the aircraft safely to an emergency landing at Gimli Industrial
Park Airport, a former airbase at Gimli, Manitoba.
• The subsequent investigation revealed corporate failures and a chain of
minor human errors which combined to defeat built-in safeguards.
• In addition, fuel loading was miscalculated through misunderstanding of
the recently adopted metric system which replaced the Imperial system.
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• At the time of the incident, Canada was converting to the metric
system. As part of this process, the new 767s being acquired by Air
Canada were the first to be calibrated for the new system, using litres
and kilograms instead of gallons and pounds. All other aircraft were
still operating with Imperial units (gallons and pounds).
• For the trip to Edmonton, the pilot calculated a fuel requirement of
22,300 kilograms (49,000 lb).
• A dripstick check indicated that there were 7,682 litres (1,690 imp gal;
2,029 US gal) already in the tanks.
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• In order to calculate how much more fuel had to be added, the crew
needed to convert the quantity in the tanks to a weight, subtract that
figure from 22,300 and convert the result back into a volume.
• A litre of jet fuel weighs 0.803 kg, so the correct calculation was:
7682 litres x 0.803 = 6169 kg
22300 kg – 6169 kg = 16131 kg
16131 kg ÷ 0.803 = 20088 litres
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• Between the ground crew and flight crew, however, they arrived at an
incorrect conversion factor of 1.77 the weight of a litre of fuel in pounds.
This was the conversion factor provided on the refueller's paperwork
and which had always been used for the rest of the airline's imperial-
calibrated fleet.
• Their calculation produced:
7682 litres x 1.77 = 13597 'kg'
22300 kg – 13597 'kg' = 8703 kg
8703 kg ÷ 1.77 = 4916 litres
• They had 22,300 pounds on board instead of 22,300 kg of fuel which was
only a little over 10,000 kg, which was less than half the amount
required to reach their destination. The amount they loaded (4916 litres)
was not enough either.
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EDMONTON
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Wrong units
The Gimli Glider
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Cesium 133 is the element most commonly
chosen for atomic clocks.
Cesium atomic clocks employ a beam of
cesium atoms. The clock separates cesium
atoms of different energy levels by magnetic
field.
To turn the cesium atomic resonance which
is 9,192,631,770 Hz (Hz= cycles/second),
into an atomic clock, it is necessary to
measure one of its transition or resonant
frequencies accurately.
Cesium atomic clock
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How the NIST-F1 Cesium Fountain Clock Works
FIGURE 1: A gas of cesium atoms enters the clock's vacuum chamber. Six lasers slow the movement of the atoms, cooling them to near absolute zero and force them into a spherical cloud at the intersection of the laser beams.
FIGURE 2: The ball is tossed upward by two lasers through a cavity filled with microwaves. All of the lasers are then turned off.
FIGURE 3: Gravity pulls the ball of cesium atoms back through the microwave cavity. The microwaves partially alter the atomic states of the cesium atoms.
FIGURE 4: Cesium atoms that were altered in the microwave cavity emit light when hit with a laser beam. This fluorescence is measured by a detector (right). The entire process is repeated until the maximum fluorescence of the cesium atoms is determined. This point defines the natural resonance frequency of cesium, which is used to define the second.
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Mass and Weight
Mass (m) is the quantity of matter in an object. In SI the standard of
mass is 1 kilogram (kg). This is a large quantity for most applications
in chemistry. More commonly chemists use the unit gram (g).
Weight (W) is the force of gravity (g) on an object. It is directly
proportional to mass. The mathematical expression is
W = m . g
An object has a fixed mass, but its weight may change.
Thus, an object that weighs 100.0 kg in St. Petersbugh, Russia,
weighs only 99.6 kg in Panama (about 0.4% less).
the same object would weigh only about 17 kg on the moon.
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A modern electronic
balance
Laboratory weighing is one
of the most reliable
measurements we can make.
The mass of an object
weighing a few grams can be
determined to six or seven
significant figures.
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Volume
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Temperature
a) Freezing point
b) Boiling point
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Relative Temperatures
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Uncertainties
• A) Systematic errors.– Instrumental errors. (Thermometer constantly 2°C too low)– Error in method. (using not suitable method)– Personal errors. (Limitation in reading a scale)
• B) Random errors
- Source not known and can not be detected
• Precision– Reproducibility of a measurement.
• Accuracy– How close to the real value.
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1.4 Precision and Accuracy in Measurements
• The precision of a set of measurements refers to how closely
individual measurements agree with one another.
• The precision is good (or high) if each of the measurements in a
set is close to the average of the set.
• The accuracy of a set of measurements refers to how close the
average of the set comes to the true, or most probable, value.
• Measurements of high precision are more likely to be accurate
than those of poor precision, but even high precise measurements
are sometimes inaccurate.
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Rules for Significant Figuresin Calculations
KEY POINT: A calculated quantity can be no more
precise than the least precise data used in the
calculation
Analogy: a chain is only as strong as its
weakest link
… and the reported result should reflect this fact
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Significant Figures
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Significant Figures
Counting Sign. Fig.: from left and from first non-zero digit.
Numbers
6.29 g0.00348 g9.0 1.0 10-8
100 g = 3.14159
SignificantFigures
322
bad notationvarious
3
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Significant figures
Multiplying and dividing :
Use the fewest significant figures.
0.01208 0.236
= 0.0512 or
= 5.12 10-2
= 0.051186
Adding and subtracting :
Use the number of decimal places in the number with thefewest decimal places.
1.14 0.611.67613.416 13.4
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Significant figures
Rounding off :
3rd digit is increased if4th digit 5
Report to 3 significant figures.
10.235 12.4590 19.75 15.651
10.212.519.815.7
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Significant Figuresin Calculations
Multiplication and Division:
the reported results should have
no more significant figures than
the factor with the fewest
significant figures
1.827 m × 0.762 m = ?
EOS
0.762 has 3 sig figs so the
reported answer is 1.39 m2
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A Problem-Solving Method
Chemistry problems usually require calculations,
and yield quantitative (numerical) answers
For example,1 inch = 2.54 cm
EOS
The unit-conversion method is useful
for solving most chemistry problems –
the focus here is on “unit equivalents”
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1.5 A Problem-Solving Method
Much of the study of chemistry involves solving
problems.
The Unit-Conversion Method
In chemical calculations frequently one unit is converted
to another unit.
In these calculations a conversion unit is used to convert
one unit to another.
By using conversion units stepwisely (usually more than
one step), calculations can be performed easily and
correcly.
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Conversion units
are obtained
from tables
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Conversion
What is the mass of a cube of osmium in grams,
that is 1.25 inches on each side?
Have volume, need density= 22.48g/cm3 (from table)
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Two Examples
How many cm are in 26 inches?
26 in × cmin
2.541
= 66 cm? cm =
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Two Examples
EOS
How many mm are in 1.25 foot?
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Density
d = m/V
kg/m3 g/cm3 g/mL
Although the mass of an object remains constant as
the temperature is raised, the volume generally
increases – the object expands – and therefore its
density decreases.
It is usually necessary to state the temperature at
which a density is measured.
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Density is the ratio of mass to volume:
md = –––
VDensity can be used as a conversion factor.
For example, the density of methanol is 0.791 g/mL;
therefore, there are two conversion factors, each equal
to one:
Density: A Physical Property and Conversion Factor
0.791 g methanol–––––––––––––– and 1 mL methanol
1 mL methanol––––––––––––––0.791 g
methanol
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Measuring Density of Solids
A comparison of some densities
The liquids are as follows: Hexane (d = 0.66 g/cm3), which does not mix with water, floats on the water. Water (d = 1.00 g/cm3), which does not mix with chloroform, floats on the chloroform. Chloroform (d = 1.48 g/cm3) floats on the mercuryMercury (d = 13.6 g/cm3) at the bottom. Wood, a material of variable composition, has a range of densities. The densities listed here are representative for three types of wood. Balsa wood (d = 0.11 g/cm3) has such a low density that it floats on hexane; padouk wood (d = 0.86 g/cm3) floats on water but not on hexane; and ebony wood (d = 1.2 g/cm3) sinks in water but floats on chloroform. Liquid mercury (d = 13.6 g/cm3). is so dense that copper (d = 8.94 g/cm3) floats on it.
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Measuring volumes of irregular shapes
The volume of the
irregularly shaped
objects can be
measured by water
displacement in a
graduated cylinder.
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Determining body volume
It is easy to measure a person's mass (weight), but what about a person's volume? When submerged in water, a body displaces its own volume of water. The difference in the person's weight in air and when submerged in water equals the mass of displaced water. This mass, divided by the density of water, yields the volume of displaced water and--with an appropriate correction for the volume of air in the lungs and gases in the intestine--the person's volume (see Problem 103).
Notes:This method is used for any irregular object.
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Mass off floating wood
The floating block of
wood displaces water
from the container.
The mass of the water
displaced is equal to the
mass of the wood object.
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A pycnometer can be used to
determine the densities of liquids
very precisely.
The exact volume of the pycnometer
must be determined by first
determining the mass of the empty,
dry pycnometer, then filling it with
water of a known temperature and
determining the mass of the water
and pycnometer. Using the formula: V
= Mwater/Dwater, the volume can be
calculated.
The pycnometer is again dried, then
filled with the liquid. The mass of the
liquid, divided by the known volume,
gives the density of the liquid.
Density of Liquids
Diff: 9.9570 gVol: 9.9750 ml
Diff: 8.7680 g d: 0.8790 g/ ml
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Separations