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Either way, the universe is destined for thermodynamic equilibrium—maximum entropy. This is often called the heat death of the universe , and will mean the end of all activity. However, whether the universe contracts and heats up, or continues to expand and cools down, the end is not near. Calculations of black holes suggest that entropy can easily continue for at least 10 100 size 12{"10" rSup { size 8{"100"} } } {}  years.

Order to disorder

Entropy is related not only to the unavailability of energy to do work—it is also a measure of disorder. This notion was initially postulated by Ludwig Boltzmann in the 1800s. For example, melting a block of ice means taking a highly structured and orderly system of water molecules and converting it into a disorderly liquid in which molecules have no fixed positions. (See [link] .) There is a large increase in entropy in the process, as seen in the following example.

Entropy associated with disorder

Find the increase in entropy of 1.00 kg of ice originally at 0º C size 12{0°C} {} that is melted to form water at 0º C size 12{0°C} {} .


As before, the change in entropy can be calculated from the definition of Δ S size 12{ΔS} {} once we find the energy Q size 12{Q} {} needed to melt the ice.


The change in entropy is defined as:

ΔS = Q T . size 12{ΔS= { {Q} over {T} } } {}

Here Q size 12{Q} {} is the heat transfer necessary to melt 1.00 kg of ice and is given by

Q = mL f , size 12{Q= ital "mL" rSub { size 8{f} } } {}

where m size 12{m} {} is the mass and L f size 12{L rSub { size 8{f} } } {} is the latent heat of fusion. L f = 334 kJ/kg size 12{L rSub { size 8{f} } ="334"" kJ/kg"} {} for water, so that

Q = ( 1.00 kg ) ( 334 kJ/kg ) = 3 . 34 × 10 5 J. size 12{Q= \( 1 "." "00"" kg" \) \( 3 "." "34"" kJ/kg" \) =3 "." "34" times "10" rSup { size 8{5} } " J"} {}

Now the change in entropy is positive, since heat transfer occurs into the ice to cause the phase change; thus,

Δ S = Q T = 3 . 34 × 10 5 J T . size 12{ΔS= { {Q} over {T} } = { {3 "." "34" times "10" rSup { size 8{5} } " J"} over {T} } } {}

T size 12{T} {} is the melting temperature of ice. That is, T = C=273 K size 12{T=0°"C=273 K"} {} . So the change in entropy is

Δ S = 3 . 34 × 10 5 J 273 K = 1.22 × 10 3 J/K. alignl { stack { size 12{DS= { {3 "." "34"´"10" rSup { size 8{5} } " J"} over {"273 K"} } } {} #" "=1 "." "22"´"10" rSup { size 8{3} } " J/K" "." {} } } {}


This is a significant increase in entropy accompanying an increase in disorder.

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The diagram has two images. The first image shows molecules of ice. They are represented as tiny spheres joined to form a floral pattern. The system is shown as ordered. The second image shows what happens when ice melts. The change in entropy delta S is marked between the two images shown by an arrow pointing from first image toward the second image with change in entropy delta S shown greater than zero. The second image represents water shown as tiny spheres moving in a random state. The system is marked as disordered.
When ice melts, it becomes more disordered and less structured. The systematic arrangement of molecules in a crystal structure is replaced by a more random and less orderly movement of molecules without fixed locations or orientations. Its entropy increases because heat transfer occurs into it. Entropy is a measure of disorder.

In another easily imagined example, suppose we mix equal masses of water originally at two different temperatures, say 20.0º C size 12{"20" "." 0°C} {} and 40.0º C size 12{"40" "." 0°C} {} . The result is water at an intermediate temperature of 30.0º C size 12{"30" "." 0°C} {} . Three outcomes have resulted: entropy has increased, some energy has become unavailable to do work, and the system has become less orderly. Let us think about each of these results.

First, entropy has increased for the same reason that it did in the example above. Mixing the two bodies of water has the same effect as heat transfer from the hot one and the same heat transfer into the cold one. The mixing decreases the entropy of the hot water but increases the entropy of the cold water by a greater amount, producing an overall increase in entropy.

Second, once the two masses of water are mixed, there is only one temperature—you cannot run a heat engine with them. The energy that could have been used to run a heat engine is now unavailable to do work.

Questions & Answers

Why is there no 2nd harmonic in the classical electron orbit?
Shree Reply
how to reform magnet after been demagneted
Inuwa Reply
A petrol engine has a output of 20 kilowatts and uses 4.5 kg of fuel for each hour of running. The energy given out when 1 kg of petrol is burnt is 4.8 × 10 to the power of 7 Joules. a) What is the energy output of the engine every hour? b) What is the energy input of the engine every hour?
Morris Reply
what is the error during taking work done of a body..
Aliyu Reply
what kind of error do you think? and work is held by which force?
I am now in this group
theory,laws,principles and what-a-view are not defined. why? you
Douglas Reply
A simple pendulum is used in a physics laboratory experiment to obtain an experimental value for the gravitational acceleration, g . A student measures the length of the pendulum to be 0.510 meters, displaces it 10 o from the equilibrium position, and releases it. Using a s
Emmanuel Reply
so what question are you passing across... sir?
Two masses of 2 kg and 4 kg are held with a compressed spring between them. If the masses are released, the spring will push them away from each other. If the smaller mass moves off with a velocity of 6m/s, what is the stored energy in the spring when it is compressed?
Emmanuel Reply
54 joule
Reduce that two body problem into one body problem. Apply potential and k. E formula to get total energy of the system
i dont think dere is any potential energy... by d virtue of no height present
there is compressed energy,dats only potential energy na?
yes.. but... how will u approach that question without The Height in the question?
Can you explain how you get 54J?
Because mine is 36J
got 36J too
OK the answer is 54J Babar is correct
Conservation of Momentum
woow i see.. can you give the formula for this
Two masses of 2 kg and 4 kg are held with a compressed spring between them. If the masses are released, the spring will push them away from each other. If the smaller mass moves off with a velocity of 6m/s, what is the stored energy in the spring when it is compressed? Asume there is no external force.
Emmanuel Reply
Please help!
please help find dy/dx 2x-y/x+y
By using the Quotient Rule dy/dx = 3y/(x +y)²
may be by using MC^2=MC^2 and Total energy=kinetic energy +potential energy so 1st find kinetic energy and den find potential energy which is stored energy
i think i m correct
But how?
what's the big bang?
kwame Reply
yes what is it?
it is the explanation of how the universe began
it is a theory on how the universe began. to understand more I would suggest researching the topic online.
thanks guys
if a force of 12N is applied to load of 200g what us the work done
Joshua Reply
We can seek accelation first
we are given f=12 m=200g which is 0.2kg now from 2nd law of newton a= f/m=60m/s*2 work done=force applied x displacement cos (theta) w= 12x60 =720nm/s*2
this very interesting question very complicated for me, í need urgent help. 1,two buses A and B travel along the same road in the same direction from Harper city (asume They both started from the same point) to Monrovia. if bus A maintains a Speedy of 60km/h and bus B a Speedy of 75km/h, how many
hours Will it take bus B to overtake bus A assuming bus B starts One hour after bus A started. what is the distance travelled by the buses when They meet?.
pls í need help
4000 work is done
speed=distance /time distance=speed/time
now use this formula
what's the answer then
great Mudang
please Ana explain 4000 ?
hey mudang there is a product of force and acceleration not force and displacement
@Mohammed answer is 0.8hours or 48mins
its not possible
í want the working procedure
the answer is given but how Will One arrive at it. the answers are 4hours and 300m.
physics is the science that studies the non living nature
isidor Reply
ancient greek language physis = nature
what is phyacs
technical Reply
if i am going to start studying physics where should i start?
I think from kinematics
You can find physics books at the library or online. That's how I started.
And yes, kinematics is usually where you can begin.
study basic algebra and calculus and can start from classical mechanics
yes think so but dimension is the best starting point
3 formula's of equations of motion
benjamin Reply
vf=vi+at........1 s=vit+1/2(at)2 vf2=vi2+2as
solve the formula's please
those are the three .. what you wanna solve ?
For first equation simply integrate formula of acceleration in the limit v and u
For second itegrate velocity formula by ising first equation
similarly for 3 one integrate acceleration again by multiplying and dividing term ds
any methods can take to solve this eqtions
a=vf-vi/t vf-vi=at vf=vi+at......1
suppose a body starts with an initial velocity vi and travels with uniform acceleration a for a period of time t.the distance covered by a body in this time is "s" and its final velocity becomes vf
what is the question dear
average velocity=(vi+vf)/2 distance travelled=average velocity ×time therefore s=vi+vf/2×t from the first equation of motion ,we have vf =vi+at s=[vi+(vi+at)]/2×t s=(2vi+at)/2×t s=bit+1/2at2
find the distance
Two speakers are arranged so that sound waves with the same frequency are produced and radiated through a room. An interference pattern is created. Calculate the distance between the two speakers?
Hayne Reply
How can we calculate without any information?
I think the formulae used for this question is lambda=(ax)/D
Practice Key Terms 3

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