CHAPTER 1
INTRODUCTION TO CHEMISTRY AND MEASUREMENT
•Introduction to quantitative chemistry
•Measurement and Significant Figures
•SI Units
•Derived Units
INTRODUCTION TO QUANTITATIVE
CHEMISTRY
WHAT IS CHEMISTRY ?
 Chemistry can be defined as the science that deals with the
materials of the universe and the changes that these materials
undergo.
Ex: Air, Water, Rock, Animal, Gas, Cloth, Oil
 Concerned with composition, behavior/reaction, structure,
properties of matter and the changes
DEVELOPMENT OF MODERN CHEMISTRY
 Thousands before century : human used natural materials to make the
useful products. Ex : fermenting beer and wine, extract chemicals from
plants for medicine and perfume.
 Discovery of fire : develop ceramics, glass and metals.
18th century : Antoine-Laurent Lavoisier discover all materials composed
of ‘atoms’ and can arrange into ‘molecules’.
Development of instrument and apparatus. Ex : Battery, liquid-crystal
display (LCD)-cell phone, computer, TV.
EXPERIMENT AND EXPLANATION
 Experiment is an observation of natural phenomena carried out
in a control manner to get the rational conclusions/result.
 Process of scientific method (method the scientist use to study
the nature):
• Observation – laws, hypothesis and theories
• Conducting more experiments
 Experiments and their explanation depend on creativity and individually
of researcher.
MEASUREMENT AND SIGNIFICANT FIGURES
 Measurement is the comparison of a physical quantity to be
measured with a unit of measurement (fixed standard of
measurement)
 Length (m), Temperature (K), Time (s), Mass (g).
Accuracy – how close the measured value is to the true or
accepted value.
Precision – how close a set of values obtained from
measurement of quantity.
Example???
RULES OF SIGNIFICANT FIGURES
 All non-zero digits are considered significant. Ex: 91, 234, 3.678
 Zeros appearing anywhere between two non-zero digits are
significant. Ex: 101.12 have five significant digits.
 Leading zeros are NOT significant. Ex: 0.00052 has two significant
digits.
RULES OF SIGNIFICANT NUMBER
 Trailing zeros in a number containing a decimal point are
significant. Ex:12.2300 has six significant digits.
The last significant digit of a number may be underlined; for
example, 20000 has two significant digits.
 A decimal point may be placed after the number; Ex: "100.“
indicates three significant digits are meant.
ROUNDING
Rounding is the procedure of dropping non significant digits in
calculation result or replacing it by another value that is
approximately equal but shorter and simpler.
 If digit is greater or equal to 5, add 1 to the digit to be retained
and drop all digits to the right. Ex: Rounding 1.2151 to three
significant figures gives 1.22
If digit is less than 5, simply drop it and all the digit to the right.
Ex: Rounding 1.2143 to three significant figures gives 1.21
EXERCISE
Round off each of the following numbers to three
significant figures.
a) 63.351
e) 0.0020285
b) 0.0000004399
f) 90960
c) 10249000
g) 3.79745
d) 555.50
h) 7296.38
ANSWER
Round off each of the following numbers to three
significant figures.
a) 63.351 = 63.4
b) 0.0000004399 = 0.000000440
e) 0.0020285 = 0.00203
f) 90960 = 91000
c) 10249000 = 10200000
g) 3.79745 = 3.80
d) 555.50
h) 7296.38 = 7300
= 556
MULTIPLICATION
In multiplying two numbers, we have to find the least number of
significant figures. This is the number of significant figures in the
answer.
Example : 0.024 x 1244 = 29.856 ≈ 30
DIVISION
In dividing two numbers, the answer should contained the least
number of significant figures from the two numbers.
Example : 528 / 12.14 = 43.49259 ≈ 43.5
ADDITION AND SUBTRACTION
In adding or subtracting, round to the least number
of decimal places in the data.
Example : 42.56 + 39.460 + 4.1 = 86.120 ≈ 86
SI UNIT (International System)
 International System of Units (SI) specifies a set of
seven base units and also known as the metric
system
 Divide into two:
• Base Unit and Prefixes (Length, Mass,
Temperature)
• Derived unit ( Pressure, Volume, Density)
SI BASE UNIT
QUANTITY
UNITS
SYMBOL
Length
Meter
m
Mass
Kilogram
kg
Time
Second
s
Temperature
Kelvin
K
Amount of
Mole
mol
Ampere
A
Substance
Electric current
US UNIT
QUANTITY
UNITS
Length
Inch, Feet, Miles
Mass
Pound (lb), Ounce
Temperature
Fahrenheit (F)
Volume
Gallons
SI PREFIX
MULTIPLE
PREFIX
SYMBOL
1012
tera
T
109
giga
G
106
mega
M
103
kilo
k
10-1
deci
d
10-2
centi
c
10-3
milli
m
10-6
micro
µ
10-9
nano
n
UNITS CONVERSION
Relationships of Some US & Metric Units
1 inch = 2.54 cm
= 25.4 mm
1 lb = 0.4536 kg
1 mile = 1.609 km
= 5280 ft
1 ft = 30.38 cm
= 12 inch
1 gallon = 3.79 L
1 qt = 0.9464 L
Temperature
K = °C + 273.15
°C = K - 273.15
°C = (°F - 32) ÷ 1.8
°F = (°C × 1.8) + 32
DERIVED UNIT
 Derived by combination SI base units
 Ex 1: Velocity, v = Distance (m) = ms-1
Time (s)
 Ex 2: Acceleration, a = Velocity = ms-2
Time (s)
DERIVED UNIT
 Ex 3: Volume, V
• Cubic Volume
• Cylinder Volume
=Area x thickness
= m2 x m
= m3
= Area x height
= r2 x m
= m3
 Ex 4: Density, d = Mass (kg)
= kgm-3
Volume (m3)
Density of water = 1000kgm-3
1 mL = 1 cm3
DERIVED UNIT
 Ex 5: Force, F
= Mass (kg) x Acceleration (ms-2)
= kgms-2
= Newton (N)
 Ex 6: Pressure, P = Force (N) = Nm-2 = Pascal (Pa)
Area (m2)
1 atm = 101.325 kPa = 1.01325 Bar
1 atm = 14.7 psi
1 atm = 760 mmHg = 760 Torr
EXERCISE
1. Pressure: 287.7 Psi
Convert this pressure into kPa & Bar
2. Pressure: 55 mmHg
Convert this pressure into Psi
ANSWER
1. Pressure: 287.7 Psi
Convert this pressure into kPa & Bar
14.7 psi = 101.325 kPa
1 psi = 101.325 kPa = 6.893 kPa
14.7
So, 287.7 psi = 287.7(6.893 kPa) = 1983.12kPa
= 19.83 Bar
ANSWER
2. Pressure: 55 mmHg
Convert this pressure into Psi.
760 mmHg = 14.7 psi
1 mmHg = 14.7 psi
760
So, 55 mmHg = 55(14.7 psi) = 1.06 psi
760