GENERAL CHEMISTRY 2: LAWS OF THERMODYNAMICS
VOCABULARY:
Endothermic Process: Process that absorbs heat from the surroundings.
Exothermic Process: Process that gives off heat to the surroundings.
Enthalpy: A thermodynamic quantity used to describe heat changes taking place at constant pressure.
Entropy: A measure of the randomness or disorder of a system.
Collision Theory: It states that for a chemical reaction to occur, the reacting particles must collide
with one another.
Law of Conservation of Energy: “Energy can be converted from one form to another but cannot be
created or destroyed.”
Three Laws of Thermodynamics
1st Law: Energy of the universe is constant
2nd Law: Entropy of the universe increases.
3rd Law: At absolute zero, the entropy of a perfect crystal is zero
SPONTANEOUS PROCESS
A spontaneous process is a physical or chemical change that occurs by itself. These processes occur
without requiring an outside force and continue until equilibrium is reached. A nonspontaneous
process, on the other hand, will not take place unless it is “driven by the continual input of energy
from an external source.
Process have natural tendency to occur in one direction under a given set of conditions. Water will
naturally flow downhill, but uphill flow requires outside intervention such as the use of a pump. A
process that is spontaneous in one direction under a particular set of ocnditions is nonspontaneous in
the reverse direction. At room temperature and typical atmospheric pressure, for example, ice will
spontaneously melt, but water will not spontaneously freeze.
Eg.
1. Heat flows from a hotter object to a colder one
2. An iron object rusts in moist air
3. Sugar dissolves in a cup of coffee
ENTROPY
Entropy is a measure of the randomness or disorder of a system. Entropy of the universe is always
increasing.
*First law of thermodynamics tells us that the energy of the universe can never be depleted or grow.
For example, the energy stored in a log of wood is not lost when you ignite it. It just transfers into
heat.
THE ANALOGY OF A LIBRARY
Two libraries contain same number of books. The first library, all books are neatly arranged. The
second library, the books are arranged randomly. These 2 libraries differ in the quality of service they
can provide. Entropy, loosely, is a measure of quality of energy in the sense that the lower the
entropy, the higher the quality. Energy stored in the first library has lower entropy. Energy stored in a
chaotic way has high entropy.
Can we also decrease entropy?
Yes, we can decrease entropy by storing energy in a more efficient way. For example, by freezing
water in ice cubes. But, by doing so, we use energy and create heat. The increase in entropy created
by decreasing entropy will always be higher. Entropy never decreases it strives to attain a maximum.
The Heat Death of the Universe
Ancient cultures worshiped the sun as the bringer of life and they weren’t far wrong. The sun is the
ultimate steam engine, bringing us photosynthesis, liquid water and much more besides. On the other
hand, it is the driving force of universal corruption, acting as a massive entropy bomb.
Following the increase of entropy, the dissipation of matter and energy goes on until our universe
becomes so infinitely disordered that entropy can no longer increase and events come to an end. All
of matter will reach a thermal equilibrium where everything don’t have the capacity to do work
anymore. Eventually, leading to a stop.
