Thermodynamics and Statistical Mechanics

Thermodynamics is the study of energy conversion between heat and mechanical work which leads to the macroscopic properties such as temperature, volume, and pressure. Statistical mechanics is the application of probability theory to study the thermodynamic behavior of systems of a large number of particles.

3,276 Questions
Science
Thermodynamics and Statistical Mechanics

Is mica a good or bad conductor of heat?

Mica is not a good conductor of heat and consequently is often used for its insulating properties.

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Thermodynamics and Statistical Mechanics

How does convection current work using a kettle?

The element at the bottom of the kettle heats the water that's close to it. This water rises (warm water is lighter than cold), and is replaced by cold water. The cold water gets heated, and the cycle repeats itself until the water's temperature triggers the kettles thermostat to switch it off.

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Chemistry
Thermodynamics and Statistical Mechanics

What is an isoentropic process?

An isoentropic process is a chemical or thermodynamic process in which entropy does not change. An example a reversible adiabatic process is isoentropic.

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Physics
Thermodynamics and Statistical Mechanics

Why does convection occur in fluids but not solids?

In a solid, atoms and molecule are fixed in place and the material of a solid does not flow, so there can be no convection.

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Physics
Thermodynamics and Statistical Mechanics

Corollary of first law of thermodynamics?

FIRST COROLLARY OF THE 1ST LAW:

-the application of the conservation of energy to the closed system.

Closed system is also known as "control mass". It could either be a non-flow or steady flow closed system.

SECOND COROLLARY OF THE 1ST LAW:

-the application of the conservation of energy to an open system.

Open system is also called "control volume". There are 2 types of open system. The unsteady/transient flow open system.

*control surface= boundary

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Science
Thermodynamics and Statistical Mechanics

What is the transfer of thermal energy by the movement of liquid or gas?

Convection is the process of thermal energy (heat energy) transfer through movement of a fluid (liquid or gas).

In essence, a region of a material that is hot can be said to contain thermal energy and the physical transport of that material to a new place also transports the thermal energy.

Most often we discuss convection that occurs naturally as a result of density changes in a fluid as a result of temperature differences. It is like the old saying, "Hot air rises." What that means is hot air has a lower density than cold air and is more buoyant than the cold air around it and so is pushed upward. The same principle applies to most liquids and gasses. Convection currents, and the associated heat transfer, are the reason that insulation is put in the walls of a building. The insulation slows the movement of air and hence the rate of heat transfer. Normal insulation such as fiberglass does not do inhibit thermal conduction or radiative heat transfer which are the other two forms of heat transfer.

One also hears the term, "forced convection" which usually means moving air with the use of a fan or blower, though the term can be perfectly well applied to any forced movement of any fluid. This also transfers thermal energy from one location to another, of course, and is the way most modern homes are heated and cooled.

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Air Compressors
Thermodynamics and Statistical Mechanics

How are materials cooled to cryogenic condition?

  1. Air is compressed to very high pressure until it liquifies.
  2. This produces hot high pressure liquid air in a pressure vessel.
  3. The hot liquid air is allowed to cool back to ambient temperature.
  4. This reduces the pressure some, but it still must be stored in a pressure vessel to keep it liquid.
  5. The pressure vessel is now carefully vented to permit the gasses in the liquid air with higher boiling points evaporate.
  6. This causes the temperature of the remaining liquid air to drop, stopping evaporation.
  7. The liquid air can now be transfered to a dewar at atmospheric pressure and ambient temperature, with minor loss to evaporation.
  8. By allowing it to continue to evaporate and collecting the gasses that evaporate off and recompressing them as above, you can get colder and colder cryogenic gasses as well as recapturing with little loss the warmer ones that evaporated. This process is called fractional liquefaction.
  9. To get to the coldest liquid helium, you must let it cool itself by self evaporation of the warmest atoms in the liquid. After this point is reached laser beam traps can hold the helium and kick out more barely warmer atoms taking the residue down to about 10E-6 Kelvin.
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Thermodynamics and Statistical Mechanics

How is thermodynamic probability related to entropy?

it entirely depend on what kind of a system you are working with. g is the probablity (number of accessible states) and k ln g is entropy and probablity is directly related to g

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Physics
Chemistry
Thermodynamics and Statistical Mechanics

What is the first law of thermodynamics?

Conservation of Energy

The first law of thermodynamics is essentially that energy cannot be created or destroyed, but only transferred into or out of a system. Stated in other terms:

The increase in the internal energy of a thermodynamic system is equal to the amount of heat energy added to the system, less any energy expended or transferred (as through work).

For example, if a cold object is put in contact with a hot object, the hot object will transfer heat (energy) to the cold one. The amount of energy lost by the hot object is equal to the amount of energy gained by the cold one.

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Cosmology
Nuclear Physics
Electromagnetic Radiation
Thermodynamics and Statistical Mechanics

What are the best physics project topics?

The best physics project topics to study depends on what you find interesting.

If you find everyday things like motion, pendulums, and collisions interesting, study mechanics.

If you find things like optics, circuits, and electricity interesting, study electromagnetism.

If you find things like statistics, temperature, and entropy interesting, study thermodynamics.

If you find things like time dilation, the speed of light, and black holes interesting, study relativity.

If you find things like the universe, dark matter, and star formation interesting, study cosmology, astrophysics, and nuclear physics.

If you find things like particles, accelerators, atomic bombs and unified force theories interesting, first study quantum mechanics, then study nuclear and particle physics.

If you meant what are the best physics project topics to do as a science experiment, use the guidelines I stated above, but stick to the first three topics; mechanics, electromagnetism, and thermodynamics.

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Technology
Thermodynamics and Statistical Mechanics

Why the heater is not placed near the top of the kettle?

The reason for this is because the hot water rises and as the cold water circulates to the bottom it gets heated and the cycle continues until the temperature is the same throughout the body of water or the power is turned off.

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Thermodynamics and Statistical Mechanics

Why does the total energy in an isolated system remain constant?

That's the way our Universe works. The "why" is a bit tricky to answer; according to Noether's Theorem, it is related to the fact that the laws of physics don't change over time! However, Noether's Theorem involves some pretty advanced math.

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Physics
Thermodynamics and Statistical Mechanics

What is permanent set in elasticity?

The deformation remaining after a specimen has been stressed in tension for a definite period, and released for a definite period. For creep tests, it is the residual, unrecoverable deformation after the load, causing the creep, has been removed for a substantial and definite period of time.

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Job Training and Career Qualifications
Salary and Pay Rates
Thermodynamics and Statistical Mechanics

How much does an automotive engineer make?

$60,000

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Chemistry
Thermodynamics and Statistical Mechanics
Metal and Alloys

What is complete solubility in relation to thermal equilibrium diagrams for alloys?

Field of one phase (compared to two phase field, etc)

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Chemistry
Science Experiments
Thermodynamics and Statistical Mechanics

What is sublimation in thermodynamics?

Sublimation is a product going from solid state directly to gas state. Carbon dioxide does this--when you lower CO2 to the condensation point it becomes dry ice.

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Physics
Thermodynamics and Statistical Mechanics

Why are there no machines that use energy with 100 percent efficiency?

From a practical standpoint there are no machines that use energy with 100% efficiency because all movement generates some friction and hence heat and loss of efficiency. Even electrons moving through superconductors generate minute amounts of heat.

From a theoretical standpoint it's impossible to get 100% efficiency; all energy transformations increase entropy. Even if you could devise a machine with no friction, the process of converting energy from one form to another ALWAYS increases entropy. It's a result of the second law of thermodynamics.

No machine can perform with 100% thermodynamic efficiency. The process used by any machine, be it steam, electric, horse drawn, wind, or whatever, can be reduced to a simple description of heat moving from a higher temperature to a lower temperature. The Carnot cycle provides a means to calculate the maximum theoretical efficiency possible. In reality, this maximum efficiency is NEVER achieved due to heat losses, friction, etc. Note that according to the Carnot cycle, 100% efficiency is impossible. The energy input to the machine can NEVER be entirely converted to useful work. Some of the energy is ALWAYS lost as heat to the surroundings.

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Chemistry
Thermodynamics and Statistical Mechanics

Why is the density of water a maximum at 4 C?

Short Answer:

Water gets more dense as it cools until it reaches 4 degrees C. At that point, because water molecules (and the forces between them) are not spherical, they begin to exhibit a tendency to hold particular orientations at preferred separation distances that keep them further apart than was possible above 4 C. Cooling from 4 C towards 0 C removes more kinetic energy allowing the preferred orientations and separations to become more orderly, further decreasing density. At freezing, 0 C, the nonspherical forces between molecules lock them into the preferential orientations and separations of the ice crystal arrangement with a sharp increase in average separation and decrease in bulk density.

Full answer:

Most substances expand when heated and most substances have a higher density in a solid state than in a liquid one.

Water is different. Water becomes slightly lighter when it freezes. That is why ice floats.

As ice is made colder though, it follows the usual rule and gets more dense.

Water, as a liquid follows this rule - most of the time. For a small range of temperature, between 0 degrees Celcius and 4 degrees Celcius, water does the opposite and water is 0.013% denser at 4 C.

Both of the peculiar behaviors can be traced to the same origin. When any fluid freezes heat energy goes out of the fluid as the solid forms. The temperature remains constant during freezing, so the kinetic energy of the particles does not change. All the energy (heat of fusion) is a change in potential energy as a consequence of forces between particles. Usually forces between particles want to pull them closer together, but in water the forces are more complex.

Because water has a pretty strong electric dipole moment, orienting the water dipoles just right releases a lot of energy. To get them oriented "just right" involve a complex interplay of forces between each dipole and several nearby dipoles. This is further complicated by the tendency of water molecules to form hydrogen bonds.

As water cools below 4 C, kinetic energy decreases enough to allow the water molecules to spend more and more time in a preferred orientation of lower potential energy, but in order to get into this arrangement the the positions of the molecules have to move towards a regular geometric structure and that takes up more space that just being disarrayed and pushed tightly together. As the local geometric order increases and kinetic energy decreases from 4 C to 0 C, the local ordering increases and the molecules move further apart and density goes down.

When water gets to 0 C, the local geometric arrangement locks in and molecules form the regular periodic structure of ice crystals with a corresponding jump in space between molecule or rather a sudden decrease in density. Ice crystals grow as heat leaves the ice/water mixture at 0 C until the entire volume is solid ice.

If ice did not float, it would sink and the bottoms of oceans and lakes would be permanently frozen. There are planets and moons in our solar system covered in materials that do not float when frozen. We are lucky.

Data:

Water reaches it maximum density at 3.98 °C (39.16 °F).

The density of ice 0.9168 g/cm3 at 0 °C .

The density of water, 0.99984 g/cm3 at 0 °C and 0.99997 g/cm3 at 4 °C.

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Chemistry
Earth Sciences
Thermodynamics and Statistical Mechanics

What is the best heat absorbing material?

Water

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Chemistry
Clouds
Thermodynamics and Statistical Mechanics

Why does the temperature remain constant during melting and boiling although heat is being absorbed from the surroundings?

Heat is being added to ice as it melts, but that heat is going into turning the water from a solid into a liquid (breaking intermolecular bonds), rather than increasing the temperature. This is also true when it boils, and that is why a boiling pot of water won't reach a higher temperature than 100 °C.

When something changes phase from solid to liquid, or from liquid to gas, it takes energy to break the intermolecular interactions. These interactions between the water molecules are what make it solid. When you have ice, these interactions are strongest, which is why ice is hard. Then when you have water, the interactions are not as strong, and although the water still "stays together" it is now a liquid and moves and flows freely. Then when all the interactions are broken, it become a gas, or steam, and now none of the water molecules are attached to any other molecules. Whenever it goes through a phase change like this, the energy goes into breaking up these interactions, and so the temperature stays constant until all the interactions are broken. Once all the ice is melted, or all the water has turned to steam, then any added heat will act to raise them temperature again.

See the Web Links to the left for more information about phase changes.

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Solid State Physics
Quantum Mechanics
Thermodynamics and Statistical Mechanics

What is phonon theory?

sound and other mechanical vibrations are quantized as bosonic particles called phonons.

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Biology
Thermodynamics and Statistical Mechanics

What is incompressible substance?

Nothing is inincompressible

For practical propose, it defined water as incompressible since its' compressibility is very low. To compressed water down to 99/100 of original volume you would need a pressure of 217 Bar approximately. Any normal pressure vessel would burst at such pressure. It is then considered water as incompressible.

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Physics
Mechanical Engineering
Thermodynamics and Statistical Mechanics

What are the laws of thermodynamics?

There are four laws of thermodynamics Zeroth, First, Second and Third. Zeroth law state that if two systems are in thermal equilibrium with a 3rd system then they are thermal equilibrium with each other. First law is defined by following equation dQ = dU + dW . Second law is based on the conservation of energy. Third law states that as the temperature approaches absolute 0, the entropy of the system approaches a constant min.

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Physics
Thermodynamics and Statistical Mechanics

Why is the first law of thermodynamics important?

The first law of thermodynamics is important because it is a core concept of physics . It says that energy can neither be created nor be destroyed. Energy can only be transferred into or out of a system.

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Physics
Kinematics
Thermodynamics and Statistical Mechanics
Rotation

How do you build a simple working model for physics?

COLING BELL give the lsit of working models in the wikipidea

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