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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.

1,125 Questions

Why is the second law of thermodynamics important?

The second law of thermodynamics is important because it defines the direction of natural processes - it states that energy tends to disperse or become more disorderly over time. This law helps us understand why certain processes are irreversible and why systems tend towards equilibrium. It also plays a critical role in fields like engineering, chemistry, and biology.

Why does a piece of steel heat up more than an equal mass of plastic when both absorb the same heat?

Steel has a heat capacity of about 0.49 kJ/kg/°C.

Solid plastics have a heat capacity of about 1.67 kJ/kg/°C.

It thus takes more energy to warm plastic 1 °C than to warm steel 1 °C.

As to why steel has a higher heat capacity than plastic...

It may be because plastics have more ability to absorb energy into the vibrational modes of the atoms in the long polymer chains than steel does in its fairly fixed crystaline/metal structure.

What are the heat transfer from a pot on a metal grill heated over a campfire?

You will have heat transfer to the pot by radiation from the hot coals and by a combination of conduction and convection as the hot gasses of the fire rise to the pot. You might also have some slight heating by conduction from the metal grill to the pot; the grill gets heated the same way as the pot by radiation and flames but may be slightly warmer than the pot since it is closer to the coals and lies between the flames and parts of the pot resting on it. The total heat transfer from the grill to the pot is probably minimal. We would hope that the contents of the pot get heated by the walls of the pot - by conduction and, if they are fluid, convection.

How many thermodynamics laws are there?

There are three laws of thermodynamics. The first law states that energy cannot be created or destroyed, only transformed. The second law states that heat naturally flows from hot to cold. The third law states that as temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.

Why increase the world entropy.?

The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time. In other words, as energy is transferred or transformed, the overall entropy of the system and its surroundings (the universe) will always increase. This increase in entropy is a natural consequence of energy dispersing and systems moving towards a more disordered state.

How does the energy pyramid demonstrate the laws of thermodynamics?

The energy pyramid exemplifies the laws of thermodynamics by showing the decrease in available energy as you move up trophic levels. This is due to the inefficiency of energy transfer between levels, in accordance with the second law of thermodynamics, which states that energy is lost as heat at each transfer. The pyramid's shape reflects this decrease in energy availability from producers to consumers.

Why is entropy of saturated liquid lower than saturated vapor for any pure substance?

Because to perform the change of state from the saturated

liquid to saturated vapor ( at constant presure ) you have

to add heat in the amount of the substance's evaporation

latent heat Qev . At constant pressure, temperature will stay

fixed at its saturation temperature and the increase in

entropy will be

(delta S)ev = Qev/Tsat

where (delta S)ev is the entropy increment.

Tsat is the saturation absolute temperature of the substance.

And so the saturated vapor entropy is (delta S)ev larger than

the saturated liquid entropy.

What is the overall effect of the second law of thermodynamics?

The second law of thermodynamics states that in any energy transfer or transformation, the total entropy of a closed system will always increase over time. This leads to an overall increase in disorder and a decrease in the availability of energy for useful work.

How do pipes keep warm?

Pipes keep warm in one of 3 ways:

  1. Fluid flowing through them warms the walls of the tubes by imparting some of its thermal energy to the pipe as it flows and, to a lesser extent, by dissipating the heat of friction between the fluid and the pipe as well as between the molecules in the liquid with each other as they move past each other at different speeds.
  2. Heating from its surroundings
  3. Conduction along the length of the pipe from regions along the pipe that are warmer than the colder sections of the pipe.

Why entropy is not disorder?

In my opinion entropy not only is disorder but also it attempt to make a new order by distribution of energy in universe.I want to prove this idea by a simple example.

In my view order is finding my socks easily and in the minimum of time every morning.If I want to reach to this aim opposite of of entropy trend I should be bought a hug number of socks that I can find my socks even with blindfolded.

A house full of socks how can remember order?This manner even reduce probability of finding socks for others and destroy the social order.Entropy is preference everybody to somebody.In this view entropy is a trend to social justice.

The above discussion of entropy is mostly an example of the extension of the concept of entropy from thermodynamics to analogous situations elsewhere. In statistical mechanics, the notions of order and disorder were introduced into the concept of entropy. From statistical mechanics it is possible to define and derive equations that exactly reproduce the thermodynamic equations for entropy and show that those equations match the values from traditional thermodynamics - hence they ARE the same function. Various thermodynamic processes now can be reduced to a description of the states of order of the initial systems, and therefore entropy becomes an expression of disorder or randomness.

This idea of entropy being the same as disorder or randomness has been applied to describe phenomena at the macroscopic level. Unfortunately, the analogs are not perfect and not all the mathematics that apply to entropy in thermodynamics are valid for the macroscopic phenomena where the term is so loosely applied.

What is the origin of the thermal expansion?

As a substance warms up, the molecules within it become more energetic - vibrational, rotational and translational energies increase and the molecules push apart as they are able to exert more force on each other as they bang around faster and harder.

What is the partial pressure of CO2 in bar in atmosphere if its concentration is 385 parts per million by volume and the total atmospheric pressure is 14 pis?

Assuming ideal gas behaviour for CO2 and air, the mole fraction of CO2 in air would

be 0.000385 since the data of 385 ppm are given by volume.

Then the partial pressure of CO2 in the atmospheric air is given by the product of

CO2 mole fraction and the atmosphere's total pressure.

So, p.p.CO2 = 0.000385 x 14 psi = 0.00539 psi.

Relation of psi to bar, 14.696 psi = 1.01325 bar.

Finally, p.p.CO2 = 0.00539 psi x [1.01325 bar/14.696 bar] = 3.72 x 10-4 bar

Why is the bad conductor preferred in the shape of a disc in lees disc method?

A bad conductor in the shape of a disc is preferred in Lee's disc method for thermal conductivity measurements because the disc shape ensures uniform heat flow in all directions, simplifying calculations. Additionally, the disc shape allows for easy measurement of the temperature difference across its diameter, which is crucial for determining thermal conductivity accurately.

What are the advantages and disadvantages of constant speed - capillary viscometer in polymer rheology?

Polymers tend to be quite viscous so measurements using a capillary viscometer can be quite slow. The second issue is both an advantage and disadvantage: many polymers have viscosity which vary with shear forces, in other words the viscosity changes with flow speed. A single speed is not sufficient to determine the viscosity behavior of the polymer. On the other hand, you can control the speed so with multiple measurements you can build up the viscosity profile quite nicely.

Two scientists who began the laws of thermodynamics?

Two scientists who are generally thought of as establishing the laws of thermodynamics are French physicist Nicolas Léonard Sadi Carnot who studied the efficiency of heat engines believing it was the key that could help France win the Napoleonic Wars and Scottish physicist Lord Kelvin who was was the first to formulate a concise definition of thermodynamics in 1854.

Why does capillary pipe have a very tiny hole?

Capillary pipes have very tiny holes to enhance the surface tension of the liquid inside, allowing it to rise or fall along the walls of the tube. This facilitates the movement of fluids in the capillary tube without the need for pumps and enables precise measurements in devices like thermometers and pressure gauges.

What uses a heat sink in thermodynamics?

A heat sink is used in thermodynamics to dissipate excess heat from electronic devices in order to maintain optimal operating temperatures. It works by conducting and transferring heat away from the source and into the surrounding environment, helping to prevent overheating and ensuring efficient performance of the device.

Will 2 degree water at 300 psi boil if the pressure is released?

Since the triple point of water is at 0.01 °C you could certainly boil water if you released the pressure and allowed it to drop low enough. In this case "low enough" would be down around 10 mbar (0.01 bar).

What should you limit when the thermal index exceeds 1?

When the thermal index exceeds 1, you should limit strenuous physical activity, particularly for vulnerable populations such as the elderly, children, and individuals with preexisting health conditions. It is important to stay well-hydrated, seek shade or air-conditioned environments, and avoid prolonged exposure to the heat to prevent heat-related illnesses like heat exhaustion or heat stroke.

What is specific heat value of cocoa beans?

Don't know about Coffee bean, but Coffee itself is 4.18x10^3 J/Kg C (same as water)

What is the maximum work obtainable from two bodies at temperatures T1 and T2 . i need derivation. pls help you out?

To obtain the maximum work/time (power) from two bodies at different

temperatures, you have to put an "Ideal" Heat Engine between the two

bodies. The Heat Engine works with the "Carnot Thermodynamic Cycle".

The Heat Efficiency of the Carnot Cycle Engine is called "Carnot Efficiency"

and it only depends on the Absolute Temperature of the two bodies.

Absolute Temperature also known as Thermodynamic Temperature

will be in Rankine degrees, oR, (U.S.C.S.), or Kelvins (I.S.).

The Carnot Heat efficiency is given by; eff (%) = [1 - TL/TH] x 100

where TH and TL are the High and Low Thermodynamic Temperatures of the

bodies.

So if a given Carnot Efficiency turns out be of 35%, this means that from

the heat given by the High Temperature body, 35% is converted to work

and the rest is dumped to the Low Temperature body.

How does viscosity of water vary with pressure?

The viscosity of water typically decreases with increasing pressure. This is because high pressure generally reduces the spacing between water molecules, allowing them to flow more easily past each other, resulting in lower resistance to flow and therefore lower viscosity.

What stay hot even if put in a refrigerator?

Items like insulated containers, thermos flasks, or vacuum-sealed bottles can help keep beverages or food hot even when placed in a refrigerator. The insulated design helps to maintain the temperature of the contents by minimizing heat transfer with the surrounding environment.

Is light particulate matter?

Light is made up of particles called photons, which are packets of energy. These photons have no mass but they do have momentum and behave both as particles and waves. So in a sense, light can be considered a form of particulate matter.

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