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- Entropy and the second law of
Section summary
- Entropy is the loss of energy available to do work.
- Another form of the second law of thermodynamics states that the total entropy of a system either increases or remains constant; it never decreases.
- Entropy is zero in a reversible process; it increases in an irreversible process.
- The ultimate fate of the universe is likely to be thermodynamic equilibrium, where the universal temperature is constant and no energy is available to do work.
- Entropy is also associated with the tendency toward disorder in a closed system.
Conceptual questions
A woman shuts her summer cottage up in September and returns in June. No one has entered the cottage in the meantime. Explain what she is likely to find, in terms of the second law of thermodynamics.
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Consider a system with a certain energy content, from which we wish to extract as much work as possible. Should the system’s entropy be high or low? Is this orderly or disorderly? Structured or uniform? Explain briefly.
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Explain how water’s entropy can decrease when it freezes without violating the second law of thermodynamics. Specifically, explain what happens to the entropy of its surroundings.
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Is a uniform-temperature gas more or less orderly than one with several different temperatures? Which is more structured? In which can heat transfer result in work done without heat transfer from another system?
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Give an example of a spontaneous process in which a system becomes less ordered and energy becomes less available to do work. What happens to the system’s entropy in this process?
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What is the change in entropy in an adiabatic process? Does this imply that adiabatic processes are reversible? Can a process be precisely adiabatic for a macroscopic system?
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Does the entropy of a star increase or decrease as it radiates? Does the entropy of the space into which it radiates (which has a temperature of about 3 K) increase or decrease? What does this do to the entropy of the universe?
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Explain why a building made of bricks has smaller entropy than the same bricks in a disorganized pile. Do this by considering the number of ways that each could be formed (the number of microstates in each macrostate).
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Problem exercises
(a) On a winter day, a certain house loses
of heat to the outside (about 500,000 Btu). What is the total change in entropy due to this heat transfer alone, assuming an average indoor temperature of
and an average outdoor temperature of
? (b) This large change in entropy implies a large amount of energy has become unavailable to do work. Where do we find more energy when such energy is lost to us?
(a)
(b) In order to gain more energy, we must generate it from things within the house, like a heat pump, human bodies, and other appliances. As you know, we use a lot of energy to keep our houses warm in the winter because of the loss of heat to the outside.
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On a hot summer day,
of heat transfer into a parked car takes place, increasing its temperature from
to
. What is the increase in entropy of the car due to this heat transfer alone?
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A hot rock ejected from a volcano’s lava fountain cools from
to
, and its entropy decreases by 950 J/K. How much heat transfer occurs from the rock?
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When
of heat transfer occurs into a meat pie initially at
, its entropy increases by 480 J/K. What is its final temperature?
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The Sun radiates energy at the rate of
from its
surface into dark empty space (a negligible fraction radiates onto Earth and the other planets). The effective temperature of deep space is
. (a) What is the increase in entropy in one day due to this heat transfer? (b) How much work is made unavailable?
(a)
(b)
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(a) In reaching equilibrium, how much heat transfer occurs from 1.00 kg of water at
when it is placed in contact with 1.00 kg of
water in reaching equilibrium? (b) What is the change in entropy due to this heat transfer? (c) How much work is made unavailable, taking the lowest temperature to be
? Explicitly show how you follow the steps in the
Problem-Solving Strategies for Entropy .
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What is the decrease in entropy of 25.0 g of water that condenses on a bathroom mirror at a temperature of
, assuming no change in temperature and given the latent heat of vaporization to be 2450 kJ/kg?
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Find the increase in entropy of 1.00 kg of liquid nitrogen that starts at its boiling temperature, boils, and warms to
at constant pressure.
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A large electrical power station generates 1000 MW of electricity with an efficiency of 35.0%. (a) Calculate the heat transfer to the power station,
, in one day. (b) How much heat transfer
occurs to the environment in one day? (c) If the heat transfer in the cooling towers is from
water into the local air mass, which increases in temperature from
to
, what is the total increase in entropy due to this heat transfer? (d) How much energy becomes unavailable to do work because of this increase in entropy, assuming an
lowest temperature? (Part of
could be utilized to operate heat engines or for simply heating the surroundings, but it rarely is.)
(a)
(b)
(c)
(d)
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(a) How much heat transfer occurs from 20.0 kg of
water placed in contact with 20.0 kg of
water, producing a final temperature of
? (b) How much work could a Carnot engine do with this heat transfer, assuming it operates between two reservoirs at constant temperatures of
and
? (c) What increase in entropy is produced by mixing 20.0 kg of
water with 20.0 kg of
water? (d) Calculate the amount of work made unavailable by this mixing using a low temperature of
, and compare it with the work done by the Carnot engine. Explicitly show how you follow the steps in the
Problem-Solving Strategies for Entropy . (e) Discuss how everyday processes make increasingly more energy unavailable to do work, as implied by this problem.
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Questions & Answers
the diagram of the digestive system
They formed in two ways first when one sperm and one egg are splited by mitosis or two sperm and two eggs join together
Oluwatobi
Genetics is the study of heredity
Misack
how does twins formed?
Misack
discuss biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles
the study of living organisms and their interactions with one another and their environments
AI-Robot
the study of living organisms and their interactions with one another and their environment.
Wine
discuss the biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles in an essay form
list any five characteristics of the blood cells
Shaker
lack electricity and its more savely than electronic microscope because its naturally by using of light
advantage of electronic microscope is easily and clearly while disadvantage is dangerous because its electronic. advantage of light microscope is savely and naturally by sun while disadvantage is not easily,means its not sharp and not clear
Abdullahi
cell theory state that every organisms composed of one or more cell,cell is the basic unit of life
Abdullahi
is like gone fail us
DENG
cells is the basic structure and functions of all living things
Ramadan
is organisms that are similar into groups called tara
Yamosa
in what situation (s) would be the use of a scanning electron microscope be ideal and why?
A scanning electron microscope (SEM) is ideal for situations requiring high-resolution imaging of surfaces. It is commonly used in materials science, biology, and geology to examine the topography and composition of samples at a nanoscale level. SEM is particularly useful for studying fine details,
Hilary
cell is the building block of life.
Diversity of living thing
ISCONT
Cell division is the process by which a single cell divides into two or more daughter cells. It is a fundamental process in all living organisms and is essential for growth, development, and reproduction. Cell division can occur through either mitosis or meiosis.
AI-Robot
life is defined as any system capable of performing functions such as eating, metabolizing,excreting,breathing,moving,Growing,reproducing,and responding to external stimuli.
Mohamed
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Source:
OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
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