GENERAL CHEMISTRY 2
Name: ____________________________
Grade Level: _______________________
Date: _____________
Score: ____________
LEARNING ACTIVITY SHEET
Spontaneous Process and Entropy
Background Information for the Learners (BIL)
Chemical Thermodynamics is the study of the interrelation of heat and
work with chemical reactions or with physical changes of state within the
confines of the laws of thermodynamics.
Thermodynamics is a scientific discipline that deals with the
interconversion of heat and other forms of energy. It has traditionally recognized
three fundamental laws: First Law - Energy of the universe is constant. “Energy
can be converted from one form to another, but it can never be created nor
destroyed”; Second Law - Entropy of universe increases. “The entropy of the
universe increases in a spontaneous process and remains unchanged in the
equilibrium process”; and Third Law - At absolute zero, the entropy of a perfect
crystal is 0. “The entropy of the perfect crystalline substance is zero at the
absolute zero of temperature (T = 0, K = -273.150C).”
Spontaneous process as stated in the second law is a physical or
chemical change that occurs by itself. A process that takes place without energy
from an external source. It is the time-evolution of a system which releases free
energy and it moves to a lower, more thermodynamically stable energy state.
If heat flows into surroundings (exothermic) the random motion of the
molecules in the surroundings increases. Thus, the entropy of the surroundings
increases. Entropy is a thermodynamic quantity that is a measure of
randomness and disorder. It measures how spread out or dispersed the energy
of a system is among the different possible ways that system can contain
energy. It tells whether a process or chemical reaction can occur. The
connection between entropy and the spontaneity of a reaction is expressed by
the second law of thermodynamics.
The change in entropy for a given amount of heat absorbed also
depends on temperature. If the temperature of the surroundings is high, the
molecules are already quite energetic. Therefore, the absorption of heat from an
exothermic process in the system will have relatively little impact on the motion
of the molecules and the resulting increase in entropy of the surroundings will
be small. However, if the temperature of the surroundings is low, than the
addition of the same amount of heat will cause a more drastic increase in
molecular motion and hence a larger increase in entropy.
Consider the phase changes illustrated bellow. Raising the temperature
of a substance will result in more extensive vibrations of the particles in solids
and more rapid translations of the particles in liquids and gases. At higher
temperatures, the distribution of kinetic energies among the atoms or molecules
of the substance is also broader (more dispersed) than at lower temperatures.
Thus, the entropy for any substance increases with temperature.
Source: https://openstax.org/resources/f3f96b7f897d7cd062c326b3e451634f6c3d5a20
The entropy of a substance increases (ΔS > 0) as it transforms from a
relatively ordered solid, to a less-ordered liquid, and then to a still less-ordered
gas. The entropy decreases (ΔS < 0) as the substance transforms from a gas to
a liquid and then to a solid.
Consider the illustration bellow.
Source: https://encryptedtbn0.gstatic.com/images?q=tbn%3AANd9GcSU3fNtyjImEWHO5JmAuogCgNibjoAR2urP5w& usqp=CAU
What did you observe? Water is always flows downward on its own.
But never goes upward automatically.
Learning Competency:
Predict the spontaneity of a process based on entropy.
(STEM_CG11CT-IVa-b-140)
Activity 1. COMPARE ME!
Compare the pictures in each set. A.
Rock rolled uphill and downhill. (Image Source: https://encryptedtbn0.gstatic.com/images?q=tbn%3AANd9GcRJCzeHyDYohm4N7wb00whumoo -IiZmejfrg&usqp=CAU
1. What can you say about the pictures? ________________________________
_____________________________________________________________________ ______
2. How do you compare the pictures? __________________________________
_____________________________________________________________________ ______
3. Which one is more spontaneous? Why? _____________________________
_____________________________________________________________________ ______
B.
Uphill and Downhill Skiing. (Image Source: https://encryptedtbn0.gstatic.com/images?q=tbn%3AANd9GcS7dY8nkQP2SnYSrusdCuA3qS0oJ6Sq8lACdA& usqp=CAU
1. What can you say about the pictures? ________________________________
_____________________________________________________________________
______ 4. Spoilage of food
water
______ 9. Dissolution of sand in
______ 5. Burning of chlorine
______ 10. Fireworks
Activity 3. I’M A PART OF YOU!
Entropy, S, is the thermodynamic quantity that is a measure of how
spread out or dispersed the energy of a system is among the different possible
ways that system can contain energy. It is a quantity that is generally used to
describe the course of a process, that is, whether it is a spontaneous process
and has a probability of occuring in a definite direction, or a non-spontaneous
process and will not proceed in the defined direction, but in the reverse
direction.
Most processes are accompanied by entropy change. The following are
processes that lead to an increase in entropy of the system
→
Process
Order
Disorder
Melting
Solid
→
Liquid
Vaporization
Liquid
→
Vapor
Dissolving
Solute
→
Solution
Heating
System at T1
→
System at T2 (T2 > T1)
Entropy change examples:
1. Gas in balloon spreads out into room and deflates but never a balloon
spontaneously filled with air.
►The molecules of gas at a high pressure always spread to lower pressure
regions.
2. Hot coffee in a room gets cooler and the heat spreads out into the room, but
never a cold cup of coffee being spontaneously warmed up. ►Heats always
goes from high temperature into cooler regions.
The spreading out of more concentrated molecules and the spreading out of more
concentrated energy are changes from more order to more random.
Exercise:
FACT OR BLUFF!
Directions: Write Fact on the blank if the condition illustrates entropy and
write Bluff if does not illustrates entropy. _____________1. Oxidation of
nitrogen
2. How do you compare the pictures? __________________________________
_____________________________________________________________________
3. Which one is more spontaneous? Why? _____________________________
_____________________________________________________________________
Activity 2. I’M EVERYWHERE!
A spontaneous process is one that takes place without energy from an
external source. For a chemical reaction to be spontaneous, it should proceed
as written (from left to right), without an input of energy.
An endothermic process absorbs heat from the surroundings and has a
positive value, whereas an exothermic process release heat to its surroundings
and has a negative value.
Examples of reactions
1. Combustion of methane
CH4
+
2O2 →
2. Acid-base neutralization
H+(aq) + OH-(aq)
6CO2 +
→
H2O(l)
2H2O ∆H0 = -890.4 kJ/mol
∆H0 = -56.2 kJ/mol
*Both of these reactions are very exothermic and are not reversible.
3. Solid to liquid phase transition of water
H2O(s)
→
H2O(l)
∆H0 = 6.01 kJ/mol
4. Dissolution of ammonium nitrate in water
NH4NO3(s) →
NH4+(aq)
+
NO3-(aq) ∆H0 = 6.01 kJ/mol
*Ice melting above 00C and ammonium nitrate dissolving in water are both
spontaneous process yet endothermic.
Exercise:
Directions: Classify the given situations below whether the process is
spontaneous or non-spontaneous.
______ 1. Rusting of iron in moist air
______ 6. Drying of leaves
______ 2. Decaying of radioisotopes
______ 7. Dissolving of salt
______ 3. Oxidation of gold
______ 8. Radioactive atom splits up
_____________2. Sublimation of mothballs
_____________3. Reduction of silicon
_____________4. Lighting of candles
_____________5. Flow of water up hill
_____________6. Digestion of food
_____________7. Boiling water for tea
_____________8. Flow of heat from a cold body to a hot body
_____________9. Diffusion of LPG
_____________10. Making popcorn
Activity 4. WORD SEARCH
Directions: Search and encircle the important terms being described in the
sentences below. Words can be forward, backward, vertical, horizontal, or
diagonal.
1. The scientific discipline that deals with the interconversion of heat and
other forms of energy.
2. A process of a physical or chemical change that occurs by itself.
3. The measure of randomness and disorder.
4. Process that gives off heat to the surroundings.
5. Process that absorbs heat from the surroundings.
6. The value of the product during endothermic process.
7. The value of the product during exothermic process.
8. The change of phase from solid to liquid.
9. The change of phase from liquid to gas.
10. The change of phase from solid to gas.
Activity 5. CORRECT ME IF I’M WRONG!
Directions: Write TRUE if the statement is correct but if it’s false, change the
underlined word or group of words to make the whole statement true.
____________1. If heat flows into the surroundings, the random motion of the
molecules in the surroundings decreases.
____________2. In a chemical reaction, the heat change is positive if the heat product
is lower than the heat reactant.
____________3. The heat change is negative if the heat product is greater than the
heat reactant.
____________4. Spontaneous process is reversible reaction.
____________5. Entropy changes occur when gas molecules inside the LPG tank
escape and spread out into room.
____________6. Heat flows from hotter objects to a colder one is a spontaneous
process.
____________7. Burning of fuel is an example of endothermic reaction.
____________8. Coffee granules dissolve faster in hot water than in cold water.
____________9. Melting of ice cream left on top of a table is an example of exothermic
reaction.
____________10. For a chemical reaction to be spontaneous, it should proceed
without an input of energy.
SUM UP!
1. What characterize a spontaneous process? ____________________
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2. How does spontaneity apply to a chemical reaction? ______________
_______________________________________________________
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3. How do entropy changes occur? _____________________________
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4. How is hot object in an open area gets cooler? ___________________
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Reflection:
1. I learned that_____________________________________________
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2. I enjoyed most on_________________________________________
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3. I want to learn more on_____________________________________
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References
Commission on Higher Education. (2016). General Chemistry 2 (Teaching
Guide for Senior High School). Quezon City: Commission on Higher
Education. https://www.teacherph.com/general-chemistry-2-teaching-guide/
Jessie A. Key. Introductory Chemistry-1st Canadian Edition. Chapter 18.
Chemical Thermodynamics.
https://opentextbc.ca/introductorychemistry/chapter/entropy -and-the-secondlawof-thermodynamics-2/