8
1 The Behavior of Gases and Liquids
fuel before reaching its destination. Fortunately, the pilot was able to glide to a former
military air field and make a “deadstick” landing on an unused runway. Some people
who were having a picnic on the runway were fortunately able to get out of the way in
time. There was even a movie made about this incident.
The official set of units that physicists and chemists use is the International System
of Units, or SI units. The letters SI stand for Systeme Internationale, the French name
for the set of units. In this system there are seven base units. The unit of length is the
meter (m). The unit of mass is the kilogram (kg). The unit of time is the second (s). The
unit of temperature is the kelvin (K). The unit of electric current is the ampere (A).
The unit of luminous intensity is the candela (cd). The unit for the amount of a
substance is the mole (mol). The SI units are called MKS (meter-kilogram-second)
units. Prior to 1961, most chemists and some physicists used cgs (centimeter-gramsecond) units, but we now use SI units to avoid confusion.
The newton is named for Sir Isaac
Newton, 1642–1727, the great English
mathematician and physicist who
invented classical mechanics and who
was one of the inventors of calculus.
The pascal is named for Blaise Pascal,
1623–1662, a famous French
philosopher, theologian, and
mathematician.
In addition to the seven base units, there are a number of derived units. The newton
(N) is the SI unit of force:
1 N 1 kg m s −2 (definition)
(1.1-5)
The pascal (Pa) is the SI unit of pressure (force per unit area):
1 Pa 1 N m −2 1 kg m −1 s −2 (definition)
(1.1-6)
We have enclosed these defining equations in boxes, and will enclose the most important
equations in boxes throughout the rest of the book.
A force exerted through a distance is equivalent to an amount of work, which is a
form of energy. The SI unit of energy is the joule (J):
1 J 1 N m 1 kg m 2 s −2 (definition)
(1.1-7)
The joule is named for James Prescott
Joule, 1818–1889, a great English
physicist who pioneered in the
thermodynamic study of work, heat,
and energy in a laboratory that he
constructed in his family’s brewery.
Multiples and submultiples of SI units are indicated by prefixes, such as “milli” for
1/1000, “centi” for 1/100, “deci” for 1/10, “kilo” for 1000, and so on. These prefixes are
listed inside the cover of this book. We do not use double prefixes such as millikilogram
for the gram or microkilogram for the milligram.
We will also use some non-SI units. The calorie (cal), which was originally defined
as the amount of heat required to raise the temperature of 1 gram of water by 1 ◦ C, is
now defined by:
1 cal 4.184 J (exactly, by definition)
(1.1-8)
We will use several non-SI units of pressure; the atmosphere (atm), the torr, and the bar.
1 atm 101325 Pa (exactly, by definition)
(1.1-9)
760 torr 1 atm (exactly, by definition)
(1.1-10)
1 bar 100000 Pa (exactly, by definition)
(1.1-11)
The angstrom (Å, equal to 10 −10 m or 10 −8 cm) has been a favorite unit of length
among chemists, because it is roughly equal to a typical atomic radius. Picometers are
nearly as convenient, with 100 pm equal to 1 Å. Chemists are also reluctant to abandon
the liter (L), which is the same as 0.001 m 3 or 1 dm 3 (cubic decimeter).
1 The Behavior of Gases and Liquids
fuel before reaching its destination. Fortunately, the pilot was able to glide to a former
military air field and make a “deadstick” landing on an unused runway. Some people
who were having a picnic on the runway were fortunately able to get out of the way in
time. There was even a movie made about this incident.
The official set of units that physicists and chemists use is the International System
of Units, or SI units. The letters SI stand for Systeme Internationale, the French name
for the set of units. In this system there are seven base units. The unit of length is the
meter (m). The unit of mass is the kilogram (kg). The unit of time is the second (s). The
unit of temperature is the kelvin (K). The unit of electric current is the ampere (A).
The unit of luminous intensity is the candela (cd). The unit for the amount of a
substance is the mole (mol). The SI units are called MKS (meter-kilogram-second)
units. Prior to 1961, most chemists and some physicists used cgs (centimeter-gramsecond) units, but we now use SI units to avoid confusion.
The newton is named for Sir Isaac
Newton, 1642–1727, the great English
mathematician and physicist who
invented classical mechanics and who
was one of the inventors of calculus.
The pascal is named for Blaise Pascal,
1623–1662, a famous French
philosopher, theologian, and
mathematician.
In addition to the seven base units, there are a number of derived units. The newton
(N) is the SI unit of force:
1 N 1 kg m s −2 (definition)
(1.1-5)
The pascal (Pa) is the SI unit of pressure (force per unit area):
1 Pa 1 N m −2 1 kg m −1 s −2 (definition)
(1.1-6)
We have enclosed these defining equations in boxes, and will enclose the most important
equations in boxes throughout the rest of the book.
A force exerted through a distance is equivalent to an amount of work, which is a
form of energy. The SI unit of energy is the joule (J):
1 J 1 N m 1 kg m 2 s −2 (definition)
(1.1-7)
The joule is named for James Prescott
Joule, 1818–1889, a great English
physicist who pioneered in the
thermodynamic study of work, heat,
and energy in a laboratory that he
constructed in his family’s brewery.
Multiples and submultiples of SI units are indicated by prefixes, such as “milli” for
1/1000, “centi” for 1/100, “deci” for 1/10, “kilo” for 1000, and so on. These prefixes are
listed inside the cover of this book. We do not use double prefixes such as millikilogram
for the gram or microkilogram for the milligram.
We will also use some non-SI units. The calorie (cal), which was originally defined
as the amount of heat required to raise the temperature of 1 gram of water by 1 ◦ C, is
now defined by:
1 cal 4.184 J (exactly, by definition)
(1.1-8)
We will use several non-SI units of pressure; the atmosphere (atm), the torr, and the bar.
1 atm 101325 Pa (exactly, by definition)
(1.1-9)
760 torr 1 atm (exactly, by definition)
(1.1-10)
1 bar 100000 Pa (exactly, by definition)
(1.1-11)
The angstrom (Å, equal to 10 −10 m or 10 −8 cm) has been a favorite unit of length
among chemists, because it is roughly equal to a typical atomic radius. Picometers are
nearly as convenient, with 100 pm equal to 1 Å. Chemists are also reluctant to abandon
the liter (L), which is the same as 0.001 m 3 or 1 dm 3 (cubic decimeter).