CHM 101 NOTE Dr. Falope
THERMODYNAMI CS AND ELEMENTARY THERMOCHEMI STRY
Thermodynamics can be defi ned as t he st udy of energy, energy t ransf ormat ions and it s rel
at ion t o mat t er.
Thermochemist r y (Chemical t hermodynamics) is t he st udy of t he heat energy which is
associat ed wit h chemical react ions and/or physical t ransf ormat ions. I t is a branch
t hermodynamics which deals wit h t he relat ions bet ween heat and ot her f orms of energy
(such as mechanical, elect rical, or chemical energy. Chemical t hermodynamics is governed
by t he laws of t hermodynamics.
A react ion may release or absorb energy, and a phase change may do t he same, such as
in melt ing and boiling. Thermochemist r y f ocuses on t hese energy changes, par t icularly on
t he syst em's energy exchange wit h it s surroundings. When a chemical react ion occurs, it is
accompanied by an energy change which may t ake any of several dif f erent f orms. For
example, t he energy change involved in t he combust ion of f uels like kerosene, coal, wood,
nat ural gas, et c., t akes t he f orm of heat and light . Elect rical energy is obt ained f rom
chemical react ions in bat t eries. The f ormat ion of glucose, C6H12O6 by t he process of
phot osynt hesis requires t he absorpt ion of light energy f rom t he sun. Thus, we see t hat t he
energy change t hat accompanies a chemical react ion can t ake dif f erent f orms. I n t his
lesson, you shall st udy t he react ions in which heat is eit her evolved or absorbed.
Thermodynamic Syst ems and Surrounding
In thermodynamics, we must be very precise in our use of cer tain words. The two most
impor tant of these are system and surroundings. A thermodynamic system is that par t of
the world (specifi c por tion of matter) to which we are directing our attention. System is
the specifi c par t of the universe that is of interest in the study.It normally includes
substances involved in chemical and physical changes
Ever yt hing out side t he syst em t hat has a direct inf luence on t he behaviour of t he syst em
is known as t he surroundings. The syst em and surroundings are separat ed by a boundary.
The universe = The syst em + The surroundings
I f our syst em is one mole of a gas in a cont ainer, t hen t he boundar y is simply t he inner wall
of t he cont ainer it self . The boundar y need not be a physical barrier; f or example, if our
syst em is a f act or y or a f orest , t hen t he boundar y can be wherever we wish t o defi ne it .
The syst em boundar y may be real or imaginar y, fi xed or def ormable.
, There are t hree t ypes of syst ems:
● Isolated System –An isolat ed syst em cannot exchange bot h energy and mass wit h it s
surroundings. The universe is considered an isolat ed syst em.
● Closed System –Across t he boundar y of t he closed syst em, t he t ransf er of energy
t akes place but t he t ransf er of mass doesn’t t ake place. Ref rigerat or, compression
of gas in t he pist on- cylinder assembly are examples of closed syst ems. The t ea in a
closed Thermos bot t le approximat es a closed syst em over a shor t t ime int er val.
● Open Syst em –I n an open syst em, t he mass and energy bot h may be t ransf erred
bet ween t he syst em and surroundings. A st eam t urbine is an example of an open
syst em.
Proper ties and the State of a System
Any charact erist ic of a syst em is called a proper t y. The properties of a syst em are t hose
quant it ies such as t he pressure, volume, t emperat ure, and it s composit ion, which are in
principle measurable and capable of assuming defi nit e values. There are of course many
proper t ies ot her t han t hose ment ioned above; t he densit y and t hermal conduct ivit y are
t wo examples. However, t he pressure, volume, and t emperat ure have special signifi cance
THERMODYNAMI CS AND ELEMENTARY THERMOCHEMI STRY
Thermodynamics can be defi ned as t he st udy of energy, energy t ransf ormat ions and it s rel
at ion t o mat t er.
Thermochemist r y (Chemical t hermodynamics) is t he st udy of t he heat energy which is
associat ed wit h chemical react ions and/or physical t ransf ormat ions. I t is a branch
t hermodynamics which deals wit h t he relat ions bet ween heat and ot her f orms of energy
(such as mechanical, elect rical, or chemical energy. Chemical t hermodynamics is governed
by t he laws of t hermodynamics.
A react ion may release or absorb energy, and a phase change may do t he same, such as
in melt ing and boiling. Thermochemist r y f ocuses on t hese energy changes, par t icularly on
t he syst em's energy exchange wit h it s surroundings. When a chemical react ion occurs, it is
accompanied by an energy change which may t ake any of several dif f erent f orms. For
example, t he energy change involved in t he combust ion of f uels like kerosene, coal, wood,
nat ural gas, et c., t akes t he f orm of heat and light . Elect rical energy is obt ained f rom
chemical react ions in bat t eries. The f ormat ion of glucose, C6H12O6 by t he process of
phot osynt hesis requires t he absorpt ion of light energy f rom t he sun. Thus, we see t hat t he
energy change t hat accompanies a chemical react ion can t ake dif f erent f orms. I n t his
lesson, you shall st udy t he react ions in which heat is eit her evolved or absorbed.
Thermodynamic Syst ems and Surrounding
In thermodynamics, we must be very precise in our use of cer tain words. The two most
impor tant of these are system and surroundings. A thermodynamic system is that par t of
the world (specifi c por tion of matter) to which we are directing our attention. System is
the specifi c par t of the universe that is of interest in the study.It normally includes
substances involved in chemical and physical changes
Ever yt hing out side t he syst em t hat has a direct inf luence on t he behaviour of t he syst em
is known as t he surroundings. The syst em and surroundings are separat ed by a boundary.
The universe = The syst em + The surroundings
I f our syst em is one mole of a gas in a cont ainer, t hen t he boundar y is simply t he inner wall
of t he cont ainer it self . The boundar y need not be a physical barrier; f or example, if our
syst em is a f act or y or a f orest , t hen t he boundar y can be wherever we wish t o defi ne it .
The syst em boundar y may be real or imaginar y, fi xed or def ormable.
, There are t hree t ypes of syst ems:
● Isolated System –An isolat ed syst em cannot exchange bot h energy and mass wit h it s
surroundings. The universe is considered an isolat ed syst em.
● Closed System –Across t he boundar y of t he closed syst em, t he t ransf er of energy
t akes place but t he t ransf er of mass doesn’t t ake place. Ref rigerat or, compression
of gas in t he pist on- cylinder assembly are examples of closed syst ems. The t ea in a
closed Thermos bot t le approximat es a closed syst em over a shor t t ime int er val.
● Open Syst em –I n an open syst em, t he mass and energy bot h may be t ransf erred
bet ween t he syst em and surroundings. A st eam t urbine is an example of an open
syst em.
Proper ties and the State of a System
Any charact erist ic of a syst em is called a proper t y. The properties of a syst em are t hose
quant it ies such as t he pressure, volume, t emperat ure, and it s composit ion, which are in
principle measurable and capable of assuming defi nit e values. There are of course many
proper t ies ot her t han t hose ment ioned above; t he densit y and t hermal conduct ivit y are
t wo examples. However, t he pressure, volume, and t emperat ure have special signifi cance
