Covers the study of (mostly homogeneous) macroscopic systems from a heat/energy/entropy point of view. Maybe combine with [tag:statistical-mechanics].

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What causes a eutectic point?

What causes the melting point depression known as a eutectic point? The temperature depression of a eutectic point can be calculated from the enthaplies and entropies of fusion of the two ...
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2answers
47 views

What is the perfect Ice Cube? [on hold]

I have a freezer with -25°C temperature and Soda with +30°C. What is the ice-cube-sized material I can put in the freezer that can bring my glas of soda to the lowest temperature? Are e.g. saltwater ...
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0answers
25 views

Expression of heat by the Brownian motion

folks. I was reading a paper from PRE and I'm not sure what's going on about the following equation. So for the system composed of two heat baths governed by Brownian motion, the entropy change of the ...
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26 views

Finding root mean square speed of an ideal gas [on hold]

Again a question ive never seen in my life... The molecules of an ideal gas have a root mean square speed of 520 meters per second at a temperature of 27 degrees celcius. Calculate the r.m.s speed ...
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142 views

Does an ice cube change its core temperature as it melts?

Let's say we have an ice water solution in an ambience with room temperature, i.e. there is a permanent exchange of energy. Let's suppose the ice cubes were from the freezer, which is at $-18°C$. The ...
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87 views

Why is not the entropy of earth increasing? [on hold]

The entropy of earth is not increasing significantly in the past billions of years. So what is the reason? It must be because of the sunshine. But I still do not have a concrete picture.
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119 views

Doping in physics [on hold]

compare and contrast the principle involved in doping and bonding. Why do increase in thermal agitation in semiconductor result in increase in conductivity
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25 views

thermodynamics question [on hold]

I've thought this question for a really long time and now i need help..... The question is "the volume occupied by a mole of liquid water at 100 degrees celcius is (1.87 exponent -5) cubic metres. ...
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38 views

Alka Seltzer Model: formulas/models requested [on hold]

This evening I became fascinated with how my Alka Seltzer tablet disintegrates over time within a small portion of Diet Lipton Citrus Ice Tea. I used a nearly frozen cup; tall, as one might request in ...
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5answers
82 views

What happens to the kinetic energy of a dropped ball when it comes to rest on the ground?

If we want to drop a ball from a height, we calculated that potential energy at bottom is zero and we say it is converted into kinetic energy. At that movement, if it is a kind of sand, we find it ...
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33 views

Why do particles in a medium have different speeds?

If thermal conduction occurs because of particles colliding with each other and imparting kinetic energy to each other, won’t the particles of an isolated medium collide with each other until the ...
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29 views

Is there anything that can be heated with least electricity? [on hold]

Do you know any element or product that can attain around 400 Celsius of temperature with the least requirement of electricity. I've been looking at the heating coils but most of them are rated as ...
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3answers
89 views

Can a Dyson Sphere around a Black Hole be built so that it would not radiate significant IR?

This is related to this question If the sphere surrounded a BH and used it as a heat dump (as well as extracting energy from it by dropping in mass) could its exterior be engineered to match the ...
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1answer
46 views

How long will pressure exist in this case?

I'm currently fabricating my project, which currently exists only on paper, and there's one question to which I have stumbled today. Suppose, that I have a pressure vessel capable of holding upto ...
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2answers
2k views

Do chemical bonds have mass?

When an exothermic reaction occurs, the energy in the chemical bonds of the reactants is partially transferred to the chemical bonds of the products. The remaining energy is released as heat. For ...
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2answers
42 views

Understanding speed distributions: Average speed, RMS speed from a graph?

So taking a look at this graph.... ![http://i.imgur.com/XUwpnSK.png][1] I want to express $A$ in terms of $N$ (total # of particles) and $V_0$. So I've found the piecewise function for $f(v)$ and ...
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22 views

bose einstein phase transition

From Carter's book Thermodynamics and Statistical Mechanics, the partition function of a bose-einstein gas in $d$ dimensions is $$ \ln(Z) = ...
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9 views

Adding thin films to a Peltier Device

I am using a peltier device maintaining a constant gradient by applying a voltage/current. My current setup is: Cold Side Peltier Device Hot Side CPU fan Was just wondering forgetting time ...
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3answers
55 views

Does a gas in a container lose kinetic energy?

When a gas is in a container, it frequently collides with the container wall, exerting pressure. However, with a collision, kinetic energy ought to be transferred from the gas molecule to the ...
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49 views

Does second law of thermodynamics imply the big bang?

Given that the second law of thermodynamics states that entropy always increases and the universe is currently not in a state of maximal entropy does that not imply that it must have started at a ...
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18 views

Making Pudding; A complicated non-equilibrium statistical process?

There are a lot of non-equilibrium processes examples given in physics literature. But some processes that are present in everyday life are not treated. As an example, the formation of pudding can be ...
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21 views

Heat engine with three thermal baths

I was wondering if we can surpass the efficiency of the Carnot engine with three thermal baths, so my question is: Is the most efficient heat engine among three temperature reservoirs a cycle ...
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0answers
26 views

Car Heating due to the sun: comparison of different contributions

Let's imagine that we need to choose a car in order to minimize the Temperature that the inner part of the car will reach after some hours under the sun. We know that two factors (if we suppose that ...
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53 views

How to calculate the energy in thermoelastic damping?

Note - I'm not 100% sure *thermoelastic damping* is the right term here - so please feel free to correct the question in case I'm wrong! If a force is applied to an elastic rod such that it ...
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1answer
21 views

Temperature and Heat question [closed]

So I have a problem about calculating the specific heat of a metal. I'm using the philosophy "Heat gained = Heat lost". The problem is: When 50g of a metal at 280C is put into a calorimeter ...
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3answers
148 views

How can space be cold? Its a vacuum? [duplicate]

I was reading that space is very cold and also it is a vacuum, and so my question is quite simple, if temperature is the "jiggling" of atoms and molecules and heat is distributed through jiggling ...
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39 views

Heat transference in my lunch [closed]

Say that I have a hot sandwich and a cool salad, both in functionally-identical plastic containers that provide no effective heat insulation. I need to stack these two containers for ease of ...
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0answers
43 views

Thermodynamics with explicit math

Nathaniel adeptly answers a question on thermodynamics by making the variable dependencies explicit: Determine the Dependence of S (Entropy) on V and T Is there a thermodynamics text that is written ...
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3answers
59 views

About energy… created, destroyed?:/

Consider a dam, in that first the hydraulic energy due to gravitational force gets converted into mechanical energy by using turbine. Then those mechanical energy is converted into electrical energy ...
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1answer
79 views

canonical ensemble that is quantum mechanical and continuous?

I do not understand what the following statements from Wikipedia mean For a canonical ensemble that is quantum mechanical and continuous, the canonical partition function is defined as $$ Z = ...
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0answers
26 views

How does fluid velocity affect the dissolution of some solute in the fluid?

Suppose we have a perfect sphere of some solute such as sugar and we place it in a fluid such as water, at a certain temperature, that is not moving. It will dissolve and diffuse into the water due to ...
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4answers
5k views

How is it possible that it can get hotter in the car than it is outside?

The Law of Thermodynamics says that two bodies will eventually have equal temperatures. How is it possible that when you leave your car in the sun, it gets hotter in the car than it is outside? Why ...
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1answer
22 views

Effect on pressure for a decrease in temperature with respect to height

If I were to have a decrease in temperature with height, $T = f(z)$, I was wondering if I could calculate the pressure like so: Could I simply combine $$ \frac{dP}{dz} = -\rho g, $$ with the ideal ...
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23 views

Single story, hotter outside, some shade from porch, enough to cool house with/without air flowing?

So, I know this question has been answered many times on the 'net, so I have some actual physics. Short Version: Check my math in the BTU paragraph. But sun/heat specifics are in whole post. I would ...
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20 views

What happens when heating water in a pressure vessel?

Suppose that I take a pressure vessel that can hold up to 2000PSI force. Now I fill it with water (not completely, but around ~90%) and now I start to heat it with direct flame, LPG gas cylinder. What ...
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25 views

Theoretical efficiency Diesel vs Otto

The efficiency for the otto cycle is defined as: equation 1: $$ n_{otto} = 1 - \frac{T_4-T_1}{T_3-T_2} $$ which can be expressed in terms of the compression ratio: equation 2:$$ n_{otto} = 1 - ...
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1answer
42 views

specific enthalpy change during phase change

consider 1 kg of water in a sealed cylinder and piston, whic exert 1 atm pressure on the system. Also water is saturated liquid at T=100$^\circ$ C. Then we give the system heat, so part of the system ...
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How to prove mathematically that the work done during irreversible process is least due to viscosity stress?

This is a known fact that the work done by the system is maximum during reversible processes & least during irreversible processes owing to the viscosity stresses. But can we prove it ...
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1answer
60 views

Does relativity objectively define entropy?

In his undergraduate text "Spacetime Physics", Wheeler points out that there is always a fourth component to momentum and energy interactions, because the internal motion of the objects involved will ...
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24 views

Heat Retention of Wine

This may seem odd and lengthy but I am going to attempt to consolidate my thoughts as much as possible. I'm sorry in advance for the length of my post and if this is confusing. I am currently ...
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2answers
67 views

Why must heat supplied in the definition of entropy be reversible? Can't it be irreversible after all it is a state function?

The definition of entropy contains the term $Q_\text{rev}$ which means the heat supplied or taken out reversibly. I thought yes it can be after all only the initial & final states are important as ...
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1answer
41 views

What color does graphene glow when heated?

If you heat graphene hot enough, what color would it glow? Is the color within the visible range?
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1answer
24 views

Thermodynamics Heat flow into Ideal Gas

I'm currently looking at University Physics by Young and Freedman, and I came across a problem that is stumping me. 19.25. Heat $Q$ flows into a monatomic ideal gas, and the volume increases while ...
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1answer
30 views

Mono-atomic gas particles coupled by spring forces don't care how many particles are involved?

I calculated the partition function of $N$ classical atoms of identical mass $m$ who all experience a mutual spring forces with identical spring constant $k$. The Hamilton is \begin{align} H = ...
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28 views

Does the density of water ice (any form of water ice) near 0K exceed the density of water at 277.15K?

In a question brought up by my chemistry class, the most we have determined is that the stability of most forms of ice decreases as the temperature decreases. What does this loss of stability do to ...
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1answer
21 views

Can the energy/power required to mix two fluids together be calculated?

Given two fluids; say for example oxygen and nitrogen gases. By simply introducing, again for example 1 liter of each gas into a closed container, the process of diffusion alone will eventually cause ...
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What is internal energy and how is it applied?

This question has partly been answered in this question which from my understanding explains that the internal energy of a system is the total kinetic and potential energy of the system excluding the ...
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1answer
76 views

7/2 versus 9/2 for diatomic heat capacity

Question I calculated the classical heat capacity of a diatomic gas as $C_V = (9/2)Nk_B$, however the accepted value is $C_V = (7/2)Nk_B$. I assumed the classical Hamiltonian of two identical atoms ...
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2answers
24 views

Dependence of heat absorbed on different ways of heating

Heat capacity depends on the delta Q (i.e small amount of heat absorbed) and delta T (i.e small change in temperature). My question is,why is the amount of heat absorbed different for different ways ...
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1answer
27 views

Thermodynamic transformation

Why it is so that any reversible thermodynamic transformation is quasi- static ? Also, Why the converge is not necessarily true ?