22
HENRY EYRING, RICHARD P. BOYCE AND JOHN D. SPIKES
grown out of a long history of human experience with the world on the
mechanical level. We tend to think of work as representing what is
done when we move an object from one place to another or from one
level to a higher level. Energy is that which is expended in carrying
out such processes. Also, from common human experiences, we get
some concept of the storage of energy. For example, if we roll a large
rock to the top of a hill we know that the rock can roll down again
spontaneously, e.g., without any further expenditure of energy on our
part. In some way, part of the energy expended in getting the rock to
the top of the hill is stored up by virtue of the higher position of the
rock. We are also acquainted with energy storage in living systems. One
example would be the storage of energy in "high-energy" phosphate
bonds which when involved in the appropriate reactions are capable of
delivering energy which the organism can utilize.
It is useful to consider the various forms of energy. We are all
acquainted with the familiar potential and kinetic energies of mechanical systems. In addition, there are a number of other forms of energy
of interest in biological systems, or of utility in calculating thermodynamic quantities. These include: (a) pressure-volume energy, the
energy required or produced when a gas is compressed or permitted to
expand; (b) surface energy which is involved when the area of a surface possessing surface tension is increased or decreased; (c) electrical
energy which is involved when an electric current flows between a
potential difference; and (d) radiant energy.
Energy is sometimes regarded as being composed of a capacity factor and an intensity factor with the total amount of energy being the
product of these two factors. Capacity factors are also termed extensive factors since their values depend on the quantity of the system involved. Intensity factors are independent of the size of the system and
are often called intensive factors. If we double the size of a particular
system, the energy content will be doubled since the capacity factor
will be doubled. The intensity factor, of course, will remain the same.
In pressure-volume energy, volume is capacity and pressure is intensity; in electrical energy the quantity of charge (coulombs) is capacity and the potential difference (volts) is intensity; and in chemical
potential energy moles of material is capacity and chemical potential is
intensity. The intensity factor, not the total energy, determines the direction of movement of energy. We can say crudely that energy of a
particular type "moves" spontaneously from a region or situation of
high intensity to one of low intensity. This movement continues until
intensity is the same in all parts of the system.
HENRY EYRING, RICHARD P. BOYCE AND JOHN D. SPIKES
grown out of a long history of human experience with the world on the
mechanical level. We tend to think of work as representing what is
done when we move an object from one place to another or from one
level to a higher level. Energy is that which is expended in carrying
out such processes. Also, from common human experiences, we get
some concept of the storage of energy. For example, if we roll a large
rock to the top of a hill we know that the rock can roll down again
spontaneously, e.g., without any further expenditure of energy on our
part. In some way, part of the energy expended in getting the rock to
the top of the hill is stored up by virtue of the higher position of the
rock. We are also acquainted with energy storage in living systems. One
example would be the storage of energy in "high-energy" phosphate
bonds which when involved in the appropriate reactions are capable of
delivering energy which the organism can utilize.
It is useful to consider the various forms of energy. We are all
acquainted with the familiar potential and kinetic energies of mechanical systems. In addition, there are a number of other forms of energy
of interest in biological systems, or of utility in calculating thermodynamic quantities. These include: (a) pressure-volume energy, the
energy required or produced when a gas is compressed or permitted to
expand; (b) surface energy which is involved when the area of a surface possessing surface tension is increased or decreased; (c) electrical
energy which is involved when an electric current flows between a
potential difference; and (d) radiant energy.
Energy is sometimes regarded as being composed of a capacity factor and an intensity factor with the total amount of energy being the
product of these two factors. Capacity factors are also termed extensive factors since their values depend on the quantity of the system involved. Intensity factors are independent of the size of the system and
are often called intensive factors. If we double the size of a particular
system, the energy content will be doubled since the capacity factor
will be doubled. The intensity factor, of course, will remain the same.
In pressure-volume energy, volume is capacity and pressure is intensity; in electrical energy the quantity of charge (coulombs) is capacity and the potential difference (volts) is intensity; and in chemical
potential energy moles of material is capacity and chemical potential is
intensity. The intensity factor, not the total energy, determines the direction of movement of energy. We can say crudely that energy of a
particular type "moves" spontaneously from a region or situation of
high intensity to one of low intensity. This movement continues until
intensity is the same in all parts of the system.