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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
What is colder a can of coke or a glass of coke?
I would say the glass of coke (served with ice-cubes in it) is colder than the can. The melting ice-cubes in the glass of coke hold it at constant freezing/melting temperature (32F), the can of coke comes out of the refrigerator at the same temperature as the refrigerator (~35F) and warms from there.
How do you find compressibility factor z for gases?
The compressibility factor, Z, for gases can be found by dividing the molar volume of the gas by the ideal gas molar volume at the same temperature and pressure. It is typically expressed as Z = Pv/(RT), where P is pressure, v is specific volume, R is the gas constant, and T is temperature. Experimental equations of state like the Van der Waals equation or the Redlich-Kwong equation can also be used to determine Z.
Why is heat energy a low grade energy and work a high grade energy?
Heat energy is considered low grade because it is diffuse and difficult to convert into useful work with high efficiency. Work, on the other hand, is considered high grade because it is organized and can be easily directed to perform specific tasks with minimal waste. This distinction is based on the Second Law of Thermodynamics, which states that energy tends to disperse and degrade over time.
How would ice cubes lower the temperature of the water?
the temperature of ice cubes are lower than the temperature of the water around them. The heat energy from the water is used up in the process of melting the ice, so the water temperature drops.
Why would a refrigerator become hot?
A refrigerator that's working normally becomes cold on the inside and hot on
at least part of the outside, usually somewhere in the back.
The refrigerator's job is to remove heat from the inside, where the food is stored.
When it does that, it must do something with the heat. It's usually built to dissipate
that heat from a series of tubes mounted on the back.
If it is hot inside the compartment, it is likely that the gas has leaked away and the compressor running hot as a result.
Is there any system which is neither intensive nor extensive?
Not really.
Intensive means that it does not depend on the quantity of mass in the system.
Extensive means that it DOES depend on the quantity of mass in the system.
It's a binary choice - either it does or does not - either it's extensive or it's intensive.
During the night after a hot day, the air inside a small house will cool faster than the air outside. As a result, the warm air inside will rise towards the ceiling, creating a pressure difference with cooler air near the floor. When windows are opened, air will flow from high to low pressure areas, causing a cool breeze to enter the house through lower windows and push warm air out through upper windows.
What is the equivalent vaporization in thermodynamic?
Vaporization is the phase transition from liquid to vapor and is equivalent to the enthalpy change of vaporization in thermodynamics. This enthalpy change represents the amount of energy required to convert a substance from liquid to vapor at its boiling point. It is a key parameter in understanding the behavior of substances during phase transitions.
Usually as a fluid moves through a pipe, it will warm up as kinetic energy and pressure is transformed to thermal energy via internal friction within the fluid and friction between the fluid and the walls. It should be noted however that as fluids enter constrictions and then expands out on the other side where pressure is much less, the temperature may actually drop while the fluid velocity increases . This phenomena is commonly observed in the functioning of refrigerators.
Why doesn't the temperature increase as the liquid changes into a gas?
During phase change from liquid to gas, the energy is used to break the intermolecular forces holding the liquid together rather than increase the temperature. This energy is called latent heat and is used to overcome the forces between molecules instead of raising the temperature. Once all the liquid has evaporated, then additional energy will go towards increasing the temperature of the gas.
Is there a formula to calcluate temperature rise within a shipping container due to direct sunlight?
Kind of.
There are a bunch of equations involved because several factors work together.
- You have to determine the angle of the sunlight because (you may have noticed this) sunlight at a shallow angle is less intense than sunlight coming straight down from directly overhead.
- You have to determine the geometry of the shipping container and how it is oriented relative to the incoming sunlight.
- You have to know the reflectivity of the surface of the shipping container.
- You have to know the thickness of the walls of the shipping container and the thermal conductivity of those walls.
- You have to know the heat capacity of the contents of the shipping container - whether it contains cargo or just air.
- You have to know the initial temperature of the shipping container and its contents.
- You need to know the temperature of the surroundings and whether there is a wind in order to be able to account for convective heat transfer to or from the container.
- You may have to know the emissivity of the shipping container and the temperature and absorbing capacity of the surroundings.
As you might guess, this gets a little complicated so, yes you could come up with a single formula but it would require knowing a lot of constants and variables and would not be simple or easy to use and the form of the equation would change as the environment changed and different factors increased and decreased in their relative importance. Most likely you would have to solve a system of equations to get your answer. You would probably get an answer a lot quicker that would serve most purposes by just going out to a shipping yard or dock and asking someone who has worked with freight for several years to give you an estimate based on their experience.
Why is conduction faster in metals?
Conduction is faster in metals because of the presence of free electrons within the metal structure. These free electrons can move quickly and easily through the metal, allowing heat to be transferred rapidly by conduction. Additionally, metals have a high thermal conductivity due to their crystalline structure, which further enhances their ability to conduct heat efficiently.
Which method of heat transfer use a medium?
Both conduction and convection require an intervening medium, but convection requires the medium to be able to move.
How does the law of thermodynamics work with a light bulb?
The first law of thermodynamics states that energy cannot be created or destroyed, only transformed. In the case of a light bulb, electrical energy is converted into light and heat energy. The second law of thermodynamics states that some energy is always lost as heat in any energy conversion process, thus not all the energy from the light bulb is converted into light.
An insulated rigid tank is a type of container used to store and transport liquids or gases, such as chemicals or fuel. It is designed with a rigid structure for durability and insulation material to maintain the temperature of the contents. These tanks are commonly used in industries where temperature control is critical for the stored materials.
Poured concrete has an R value of about 0.08/inch. Fiberglass batt has an R value of about 3.14/inch (blown fiberglass wall insulation is about 3.2/inch). From these values we can calculate that the equivalent insulating thickness of concrete would be about 3.5x3.14/0.08 = 137.4 inches.
Note that concrete blocks have a somewhat better insulating value due to the incorporated air pockets.
A 4" concrete block has an R value of about 0.2/inch
An 8" concrete block has an R value of about 0.15/inch
A 12" concrete block has an R value of about 0.1/inch
What is the methanol vapor pressure at room temperature?
Assuming by "room temperature" you mean about 77 °F (25 °C), the vapor pressure of methanol at saturation would be about 158 mmHg.
= 0.211 bar
= 21.1 kPa
= 0.208 atm
= 3.05 psia
You can estimate the vapor pressure using the formula
log10(P) = -(0.05223)a/T + b
where P is in mmHg, T is in kelvins, a = 38324, and b = 8.8017
The law of conservation states that matter cannot be created or destroyed, only transformed, which also applies to the biogeochemical cycles where elements are recycled. The laws of thermodynamics govern energy transfer and transformations, similar to how energy flows through food chains. However, biogeochemical cycles involve the cycling of nutrients through abiotic and biotic components, while food chains focus on the transfer of energy between trophic levels in an ecosystem.
How do food webs illustrate the first and second laws of thermodynamics?
Food webs illustrate the first law of thermodynamics by showing the conservation of energy within an ecosystem - energy is transferred from one organism to another as they consume and are consumed. They also demonstrate the second law by showing that energy is lost as heat during these transfers, leading to a decrease in available energy at each trophic level.
This is fairly easy to do.
Q = M.Hevap
Q = energy for phase change
M = mass
HEvap = heat of vaporization
The heat of vaporization can be obtained from steam tables, usually with a unit of kJ/kg. Convert your mass to kg and then find Q (kJ).
Then check for a conversion factor between kJ and calories.
How many joules are required to heat 22 g of water from 25 degrees C to steam at 125 degrees C?
The specific heat capacity of water between 25 C and 100 C is 4.1813 J / (g*K).
Beyond 100 C, the heat capacity of water is 2.080 J / (g*K)
So, it take 4.1813 joules of energy to heat 1 gram of water 1 degree Celsius (Kelvin).
Therefore, in order to heat 22 g of water from 25 C to 100 C (75 C), it would require:
4.1813 * 22 * 75 = 6899.145 J
And, to heat 22 g of steam from 100 C to 125 C (25 C), it would require:
2.080 * 22 * 25 = 1144 J
The combined amount of energy required would be:
6899.145 + 1144 = 8043.145 J
Well, light has to be concentrated to be hot enough to cook food, kinda like using a magnifying glass to burn stuff, even though normal sunlight can't do it alone.
A2. And don't forget that microwave ovens typically have a power of about 1kW. A 1kW infrared lamp will heat up food pretty fast.
BUT the microwaves penetrate the food to the centre, where they vibrate the water molecule. Whereas you'd have to wait for an IR lamp's heat to be conducted to the centre which will take some time by conduction.
Microwaves are a lot more penetrating than visable light. It gets absorbed easier, wheras light reflects, etc.
A boat typically uses a propeller as a device to move through water. The propeller works based on Newton's third law of motion, where the boat pushes water backwards with the propeller blades, causing an equal and opposite reaction that moves the boat forward. This action follows the principles of thermodynamics in terms of converting energy from the boat's engine into mechanical work to propel the boat forward.
What is the degree of freedom of a man climbing a spiral staircase?
The man's freedom depends on the dimensions of the staircase and the clothes he is wearing, plus any other encumbrances. For example, if the staircase is too tight to move in, or if he is straightjacketed and chained to the banister, his degree of freedom is zero. If the staircase is spacious enough for him to jump around in, he has at least three degrees of freedom for linear motion, and at least three for rotational motion. If he possesses the power of time travel or passage through other dimensions, he will have still more degrees of freedom. All of these may be curtailed by political influences, however.
