Topic 1
Introduction: Measurement,
Mathematical Operations; Introduction
to Chemistry
Measurement
Measurement, from the Greek word
"metron", meaning limited proportion is
the estimation of the magnitude of
some attribute of an object, such as its
length or weight, relative to a unit of
measurement
It involves using a measuring
instrument, such as a ruler or scale,
which is calibrated to compare the
object to some standard, such as a
meter or a kilogram
Metrology is the scientific study of
measurement
Units of Measurements
Imperial system
early used as English units then Imperial units
came to known as US Customary Units
have at times been called foot-pound-second systems
Metric System
a decimalised system of measurement based on the
metre and the gram
it has a single base unit for each physical quantity
all other units are powers of ten or multiples of ten of this
base unit
SI Units
Système International d'Unités
modern, revised form of the metric system
two types of SI units, Base and Derived Units
SI Base Units
Name
Symbol
Quantity
metre
m
Length
Kilogram
kg
mass
second
s
time
ampere
A
electric current
kelvin
K
thermodynamic temperature
mole
mol
amount of substance
candela
cd
luminous intensity
SI Prefixes
yotta,
(Y),
meaning 1024
deci,
(d),
meaning 10-1
zetta,
(Z),
meaning 1021
centi,
(c),
meaning 10-2
exa,
(E),
meaning 1018
milli,
(m),
meaning 10-3
peta,
(P),
meaning 1015
micro,
(u),
meaning 10-6
tera,
(T),
meaning 1012
nano,
(n),
meaning 10-9
giga,
(G),
meaning 109
pico,
(p),
meaning 10-12
mega,
(M),
meaning 106
femto,
(f),
meaning 10-15
kilo,
(k),
meaning 103
atto,
(a),
meaning 10-18
hecto,
(h),
meaning 102
zepto,
(z),
meaning 10-21
deka,
(da),
meaning 101
yocto,
(y),
meaning 10-24
Instruments used for measuring
Example
Convert the following measurements:
1.
2.
3.
4.
5.
34 L = _____ cc
25°F = _____ °K
2.0 mg = _____ kg
3.5 hrs = ______ s
1 x 10-5 mol = ______ mol
Example
Convert the following measurements:
(Answer)
1. 34 L = 34, 000cc
2. 25°F = 244.48 °K
3. 2.0 mg = 0.0000020 kg
4. 3.5 hrs = 12600 s
5. 1 x 10-5 mol = 0.01 mmol
Basic Mathematical Operations
MDAS rule
Perform multiplication/division first before
addition and subtraction
e.g.
Solve the following:
1.
2.
32(6+5) – 4/2 + (35+8)
{3[4+8]/6} – (2+5(6)-12)
Basic Mathematical Operations
MDAS rule
Perform multiplication/division first before
addition and subtraction
e.g.
Solve the following:
1.
2.
32(6+5) – 4/2 + (35+8) = 393
{3[4+8]/6} – (2+5(6)-12) = -14
Rounding-off Figures
Rule 1: If the digit after that being retained is
LESS than 5, the retained digit is unchanged.
Rule 2: If the digit after that being retained is
GREATER than 5, the retained digit is
increased by one.
Rule 3: f the digit after that being retained is
EQUAL to 5, what follows determines how to
round the number.
If even number, retained
If odd number, increase by 1
Example
Round to the nearest hundredths:
1.
2.
3.
4.
5.
2.3560
2.3460
2.3452
2.3453
2.3423
=
=
=
=
=
_____
_____
_____
_____
_____
Example
Round to the nearest hundredths:
(Answer)
1. 2.3560 = 2.36
2. 2.3460 = 2.35
3. 2.3452 = 2.34
4. 2.3453 = 2.35
5. 2.3423 = 2.34
Significant Figures
Guidelines for Using Significant Figures
1.
Any digit that is not zero is significant.
2.
Zeros between nonzero digits are significant.
3.
Zeros to the left of nonzero digit are not significant.
4.
If a number is greater than 1, all zeros written after the
decimal point is significant.
5.
If a number is less than 1, zeros before the nonzero digit is
not significant.
6.
For numbers that do not contain decimal point, the trailing
zeros (zero after the nonzero digit) may or may not be
significant.
7.
In addition and subtraction, the number of significant
figures in the answer is determined by the digit that has the
least number of decimal places.
8.
In multiplication and division, the number of significant
figures in the product or quotient is determined by the
original number that has the least number of significant
figures.
Significant Figures
Example:
1.
2.
3.
4.
5.
5.01
0.02120
7,100
7.10 x 103
2.456
Significant Figures
Example:
1.
2.
3.
4.
5.
5.01 = 3
0.02120 = 4
7,100 = 2
7.10 x 103 = 3
2.456 = 4
Significant Figures
Example:
1.
2.
3.
12,524.1 + 0.1193
8.60 x 2.1335
0.0154 / 1.3
Significant Figures
Example:
1.
2.
3.
12,524.1 + 0.1193 = 12524.2
8.60 x 2.1335 = 18.3
0.0154 / 1.3 = 1.2 x 10-2
Scientific Notation
In observance of significant figures, scientist
used scientific notation to express
extremely large or small numerical values.
All can be expressed in the form:
N x 10n
Scientific Notation
Step 1: Find n
Step2: Count the number of places that the
decimal point must be moved to give the
number N.
Step 3: If the decimal point has to be
moved to the left, n is a positive integer or
to the right, n is a negative integer
Scientific Notation
Example:
1.
2.
3.
568213.5
18162.07
0.000092
Scientific Notation
Example:
1.
2.
3.
568213.5 = 5.682135 x 105
18162.07 = 1.816207 x 104
0.000092 = 9.2 x 10-5
Accuracy and Precision
Accuracy
determines
how
close
a
measurement is to the true value of the
quantity that is being measured.
Precision refers to the closeness of two or
more measurements of the same quantity
with one another.
Error
Error refers to a difference between actual
behavior or measurement and the norms
or expectations for the behavior or
measurement
Two types:
1. Systematic Error (determinate)
2. Random Error (indeterminate)
Error
Chemistry
History
began with the discovery of fire
leads to the purification of metals
(metallurgy)
alchemy
Alchemy
Mission:
protoscience
to discover the elixir of
life
(fountain of youth)
to create gold through
transformation
Alchemy
Failure:
no scientific method
unable to established nomenclature
unable to reproduce experiments
Timeline
First chemists – the Moslems
Geber – the father of chemistry
Robert Boyle – alchemist turned chemist
differentiate alchemy and chemistry
Antoine Lavoisier
Timeline
Aristotle
“atomos”
John Dalton
J. J. Thomson
Ernest Rutherford
Timeline
Chadwick
Niels Bohr
E. Schrodinger
Dmitriv Mendeleyeev
Divisions of Chemistry


Inorganic chemistry is the
properties
and
reactions
compounds.
study of the
of
inorganic
Organic chemistry is the study of the structure,
properties, composition, mechanisms, and
reactions of organic compounds. In other words,
it is the study of those substances that contain
carbon.
Divisions of Chemistry



Analytical chemistry is the analysis of material samples
to gain an understanding of their chemical
composition and structure. Analytical chemistry
incorporates standardized experimental methods in
chemistry.
Biochemistry is the study of the chemicals, chemical
reactions and chemical interactions that take place in
living organisms.
Physical chemistry is the study of the physical basis of
chemical systems and processes. In particular, the
energetics and dynamics of such systems and
processes are of interest to physical chemists.
Divisions of Chemistry
Other subdivisions:
Astrochemistry
Chemical Engineering
Electrochemistry
Geochemistry
History of chemistry
Medicinal chemistry
Molecular genetics
Organometallic chemistry
Pharmacology
Phytochemistry
Supramolecular chemistry
Thermochemistry
Nuclear Chemistry
Atmospheric chemistry
Chemo-informatics
Environmental chemistry
Green chemistry
Materials science
Molecular Biology
Nanotechnology
Petrochemistry
Photochemistry
Polymer chemistry
Surface chemistry
Theoretical Chemistry