The document discusses various systems of measurement units including the English and metric systems. It provides details on the base and derived units used in each system for measuring length, volume, mass, and other quantities. It also discusses the relationships between some of the metric units and compares the English and metric systems.

1. 1
The English System of Units
There are several systems of units, each containing units for properties such as length, volume, weight, and
time. In the English system the units are defined in an arbitrary way.
Length: inch (in), foot (ft), yard (yd), mile (mi)
12 in = 1 ft 5280 ft = 1 mi
3 ft = 1 yd 1760 yd = 1 mi
Volume: fluid ounce (oz), cup (c), pint (pt), quart (qt), gallon (gal)
2 c = 1 pt 32 oz = 1 qt
2 pt = 1 qt 4 qt = 1 gal
Weight: ounce (oz), pound (lb), ton
16 oz = 1 lb 2000 lb = 1 ton
Time: second (s), minute (min), hour (h), day (d), year (y)
60 s = 1 min 24 h = 1 d
60 min = 1 h
3651
/4 d = 1 y
Practice Problem 1
Convert 6.5 feet into inches.
The Metric System
The Metric System is based on the fundamental units of measure for length, volume, and mass.
Length: meter (m)
Volume:liter (L)
Mass : gram (g)
Base units in the Metric System can be converted into units that are more appropriate for the quantity being
measured by adding a prefix to the name of the base unit. The common metric prefixes are given below.
Metric System Prefixes
Prefix Symbol Meaning
femto- F x 1/1,000,000,000,000,000 (10-15
)
pico- P x 1/1,000,000,000,000 (10-12
)
nano- N x 1/1,000,000,000 (10-9
)
micro- x 1/1,000,000 (10-6
)
milli- M x 1/1,000 (10-3
)
centi- C x 1/100 (10-2
)
deci- D x l/10(10-1
)
kilo- K x 1,000 (103
)
mega- M x 1,000,000 (106
)
giga- G x 1,000,000,000 (109
)
tera- T x 1,000,000,000,000 (1012
)
The base units of length and volume are linked in the metric system. By definition, a liter is equal to the
volume of a cube exactly 10 cm tall, 10 cm long, and 10 cm wide. Because the volume of this cube is 1000
cubic centimeters and a liter contains 1000 milliliters, 1 milliliter is equivalent to 1 cubic centimeter.
1 mL = 1cm3
The base units of volume and weight are also linked. The gram was originally defined as the mass of 1 mL of
water at 4 degrees Celsius.
1g = 1mL H2O at 4 C
Practice Problem 2:
Convert 0.135 kilometers into meters.

2. 2
Mass Versus Weight
Mass is a measure of the amount of matter in an object, so the mass of an object is constant.
Weight is a measure of the force of attraction of the earth acting on an object. The weight of an object is not
constant.
Mass is a more fundamental quantity than weight. There is no English equivalent to the verb weigh that can
be used to describe what happens when the mass of an object is measured. You are therefore likely to
encounter the terms weigh and weight for operations and quantities that are more accurately associated
with the term mass.
SI Units of Measure
In 1960 the International System of Units was proposed as a replacement for the Metric System. The seven
base units for the SI system are given below.
SI Base Units
Physical Quantity Name of Unit Symbol
length meter m
mass kilogram kg
time second s
temperature kelvin K
electric current ampere D
amount of substance mole mol
luminous intensity candela cd
Derived Si Units
The units of every measurement in the SI system must be derived from one or more of the seven base units.
Some of the common derived SI units used in chemistry are given below.
Common Derived SI Units in Chemistry
Physical Quantity Name of Unit Symbol
Density kg/m3
electric charge coulomb C (A s)
electric potential volt V (J/C)
Energy joule J (kg-m2
/s2
)
Force newton N (kg-m/s2
)
Frequency hertz Hz (s-1
)
Pressure pascal Pa (N/m2
)
velocity (speed) meters per second m/s
Volume cubic meter m3
Non-SI Units
Strict adherence to SI units would require changing directions such as "add 250 mL of water to a 1-L beaker"
to "add 0.00025 cubic meters of water to an 0.001-m3
container." Because of this, a number of units that are
not strictly acceptable under the SI convention are still in use. Some of these non-SI units are given below.
Non-SI Units in Common Use
Physical Quantity Name of Unit Symbol
Volume liter L (10-3
m3
)
length angstrom D (0.1 nm)
Pressure atmosphere atm (101.325 kPa)
torr mmHg (133.32 Pa)

3. 3
energy electron volt eV (1.601 x 10-19
J)
temperature degree Celsius EC (K - 273.15)
concentration molarity M (mol/L)
Unit Conversions
Length
1 m = 1.094 yd 1 yd = 0.9144
Volume
1 L = 1.057 qt 1 qt = 0.9464
Mass
1 g = 0.002205 lb 1 lb = 453.6 g
Practice Problem 3
The record for the Kentucky Derby is held by Secretariat, who ran the 10 furlongs in 1 minute, 59.4 seconds.
Calculate his average speed in miles per hour.
Practice Problem 4
Calculate the volume in liters of a cubic container 0.500 meter tall.
Practice Problem 5
What is the value of a gold ingot 20.0 cm long by 8.5 cm wide by 6.0 cm tall, if the mass of a cubic centimeter
of gold is 19.3 grams and the price of gold is $356 per ounce?
Elements
Any substance that contains only one kind of an atom is known as an element. Because atoms cannot be
created or destroyed in a chemical reaction, elements such as phosphorus (P4) or sulfur (S8) cannot be broken
down into simpler substances by these reactions.
Example: Water decomposes into a mixture of hydrogen and oxygen when an electric current is passed
through the liquid. Hydrogen and oxygen, on the other hand, cannot be decomposed into simpler
substances. They are therefore the elementary, or simplest, chemical substances - elements.
Each element is represented by a unique symbol. The notation for each element can be found on the periodic
table of elements.
The elements can be divided into three categories that have characteristic properties: metals, nonmetals, and
semimetals. Most elements are metals, which are found on the left and toward the bottom of the periodic
table. A handful of nonmetals are clustered in the upper right corner of the periodic table. The semimetals
can be found along the dividing line between the metals and the nonmetals.
Atoms
Elements are made up of atoms, the smallest particle that has any of the properties of the element.John
Dalton, in 1803, proposed a modern theory of the atom based on the following assumptions.
1. Matter is made up of atoms that are indivisible and indestructible.
2. All atoms of an element are identical.
3. Atoms of different elements have different weights and different chemical
properties.
4. Atoms of different elements combine in simple whole numbers to form compounds.
5. Atoms cannot be created or destroyed. When a compound decomposes, the atoms
are recovered unchanged.
Compounds
Elements combine to form chemical compounds that are often divided into two categories.
Metals often react with nonmetals to form ionic compounds. These compounds are composed of positive
and negative ions formed by adding or subtracting electrons from neutral atoms and molecules.

4. 4
Nonmetals combine with each other to form covalent compounds, which exist as neutral molecules.
The shorthand notation for a compound describes the number of atoms of each element, which is indicated
by a subscript written after the symbol for the element. By convention, no subscript is writte
Characteristics of Ionic and Covalent Compounds
Ionic Compounds Covalent Compounds
Contain positive and negative ions
(Na+
Cl-
)
Exist as neutral molecules (C6H12O2)
Solids suchs as table salt (NaCl(s))
Solids, liquids,or gases (C6H12O6(s),
H2O(l), CO2(g))
High melting and boiling points
Lower melting and boiling points
(i.e., often exist as a liquid or gas at
room temperature)
Strong force of attraction between
particles
Relatively weak force of attraction
between molecules
Separate into charged particles in
water to give a solution that conducts
electricity
Remain as same molecule in water
and will not conduct electricity
Determining if a Compound is Ionic or Covalent
Calculate the difference between the electronegativities of two elements in a compound and the average of
their electronegativites, and find the intersection of these values on the figure shown below to help
determine if the compound is ionic or covalent, or metallic.
Practice Problem 1:
For each of the following compounds, predict whether you would expect it to be ionic or covalent.
(a) chromium(III) oxide, Cr2O3
(b) carbon tetrachloride, CCl4
(c) methanol, CH3OH
(d) strontium fluoride, SrF2
Practice Problem 2:
Use the following data to propose a way of distinguishing between ionic and covalent compounds.
Compound Melting Point ( o
C) Boiling Point ( o
C)
Cr2O3 2266 4000
SrF2 1470 2489
CCl4 -22.9 76.6

5. 5
CH3OH -97.8 64.7
Practice Problem 3:
Which of the following compounds should conduct an electric current when dissolved in water?
(a) methanol, CH3OH
(b) strontium fluoride, SrF2
Fundamental Subatomic Particles
Particle Symbol Charge Mass
Electron e-
-1 0.0005486 amu
Proton p+
+1 1.007276 amu
Neutron no
0 1.008665 amu
The number of protons, neutrons, and electrons in an atom can be determined from a set of simple rules.
The number of protons in the nucleus of the atom is equal to the atomic number (Z).
The number of electrons in a neutral atom is equal to the number of protons.
The mass number of the atom (M) is equal to the sum of the number of protons and neutrons in the
nucleus.
The number of neutrons is equal to the difference between the mass number of the atom (M) and
the atomic number (Z).
Examples: Let's determine the number of protons, neutrons, and electrons in the following isotopes.
12
C 13
C 14
C 14
N
The different isotopes of an element are identified by writing the mass number of the atom in the upper left
corner of the symbol for the element. 12
C, 13
C, and 14
C are isotopes of carbon (Z = 6) and therefore contain six
protons. If the atoms are neutral, they also must contain six electrons. The only difference between these
isotopes is the number of neutrons in the nucleus.
12
C: 6 electrons, 6 protons, and 6 neutrons
13
C: 6 electrons, 6 protons, and 7 neutrons
14
C: 6 electrons, 6 protons, and 8 neutrons
Practice Problem 1:
Calculate the number of electrons in the Cl-
and Fe3+
ions.
Electromagnetic Radiation
Much of what is known about the structure of the electrons in an atom has been obtained by studying the
interaction between matter and different forms of electromagnetic radiation. Electromagnetic radiation has
some of the properties of both a particle and a wave.
Particles have a definite mass and they occupy space. Waves have no mass and yet they carry energy as they
travel through space. In addition to their ability to carry energy, waves have four other characteristic
properties: speed, frequency, wavelength, and amplitude. The frequency (v) is the number of waves (or
cycles) per unit of time. The frequency of a wave is reported in units of cycles per second (s-1
) or hertz (Hz).
The idealized drawing of a wave in the figure below illustrates the definitions of amplitude and wavelength.
The wavelength (l) is the smallest distance between repeating points on the wave. The amplitude of the
wave is the distance between the highest (or lowest) point on the wave and the center of gravity of the wave.
If we measure the frequency (v) of a wave in cycles per second and the wavelength (l) in meters, the product
of these two numbers has the units of meters per second. The product of the frequency (v) times the
wavelength (l) of a wave is therefore the speed (s) at which the wave travels through space.
vl = s

6. 6
Practice Problem 2:
What is the speed of a wave that has a wavelength of 1 meter and a frequency of 60 cycles per second?
Practice Problem 3:
Orchestras in the United States tune their instruments to an "A" that has a frequency of 440 cycles per
second, or 440 Hz. If the speed of sound is 1116 feet per second, what is the wavelength of this note?
Light and Other Forms of Electromagnetic Radiation
Light is a wave with both electric and magnetic components. It is therefore a form of electromagnetic
radiation.
Visible light contains the narrow band of frequencies and wavelengths in the portion of the electro-magnetic
spectrum that our eyes can detect. It includes radiation with wavelengths between about 400 nm (violet) and
700 nm (red). Because it is a wave, light is bent when it enters a glass prism. When white light is focused on a
prism, the light rays of different wavelengths are bent by differing amounts and the light is transformed into
a spectrum of colors. Starting from the side of the spectrum where the light is bent by the smallest angle, the
colors are red, orange, yellow, green, blue, and violet.
As we can see from the following diagram, the energy carried by light increases as we go from red to blue
across the visible spectrum.
Because the wavelength of electromagnetic radiation can be as long as 40 m or as short as 10-5
nm, the
visible spectrum is only a small portion of the total range of electromagnetic radiation.
The electromagnetic spectrum includes radio and TV waves, microwaves, infrared, visible light, ultraviolet, x-
rays, g-rays, and cosmic rays, as shown in the figure above. These different forms of radiation all travel at the
speed of light (c). They differ, however, in their frequencies and wavelengths. The product of the frequency
times the wavelength of electromagnetic radiation is always equal to the speed of light.
vl = c
As a result, electromagnetic radiation that has a long wavelength has a low frequency, and radiation with a
high frequency has a short
Practice Problem 4:
Calculate the frequency of red light that has a wavelength of 700.0 nm if the speed of light is 2.998 x 108
m/s.