# What is Phase change: Definition + 142 Threads

In chemistry, thermodynamics, and many other related fields, phase transitions (or phase changes) are the physical processes of transition between the basic states of matter: solid, liquid, and gas, as well as plasma in rare cases.
A phase of a thermodynamic system and the states of matter have uniform physical properties. During a phase transition of a given medium, certain properties of the medium change, often discontinuously, as a result of the change of external conditions, such as temperature, pressure, or others. For example, a liquid may become gas upon heating to the boiling point, resulting in an abrupt change in volume. The measurement of the external conditions at which the transformation occurs is termed the phase transition. Phase transitions commonly occur in nature and are used today in many technologies.

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1. ### Classical Looking for a thermodynamics book that 'ties it all together'

I am currently a highschool student, and while I've learnt a bit about thermodynamics such as the first and second laws, their implications, I'd like to know how that stuff relates to gases and (without going too deep into it) phase change. Due to the structure of our curriculum, I've learnt...
2. ### I What Is the Smallest Change Detected by a Multiport Interferometer?

Good morning all... please I'd like to know what's the smallest ever recorded change in phase or wavelength any multiport interferometer has ever been able to detect. And which multiport interferometer detected it.
3. ### I Will Heating a Sealed Container Cause All Liquid to Convert to Vapor?

Please can one explain what is exactly gonna happen if we have closed container and liquid is present in it and we heat from bottom ? Then whole liquid will converted into vapour or not ? But during the phase change both system in dynamic equilibrium. If both phases are in dynamic equilibrium...
4. ### Python Thermal lattice Boltzmann model ignoring source term -- python code help please

LBM model for phase change- relevant equations found here. Also here. #Thermal LBM #solves 1D 1 phase phase-change #D2Q5 Lattice nx=100 # the number of nodes in x direction lattice direction ny=5 # the number of nodes in y...
5. ### B Phase Change in Light: A & B Signal Reflections

I would appreciate knowing if there is any error in the mechanics illustrated in this animation with respect to phase change in the signal reflections shown at A and B, or in the description accompanying it. I have embedded the description with the animation and included it in this post for...
6. ### A Heat exchange in a thermal storage based on phase change materials

Hello, I want to model a thermal battery based on phase change materials (PCM). It is a plate heat exchanger immersed in a PCM bath. The diagram is given in the attached file. I want to determine the temperature at each moment and from everywhere in the battery. The hypotheses are the...
7. ### Finding equilibrium temperature when there are phase changes

If there weren't phase changes occurring I know that the temperature equilibrium would be ##T_e=\frac{m_{ice}c_{ice}T_{ice}+m_{w}c_{w}T_{w}}{m_{ice}c_{ice}+m_{w}c_{w}}##. Now, by repeating the reasoning to get the above formula (##\sum \Delta Q=0##) and adding the phase changes of the water...
8. ### Incorrect Calculation of Time for Reactor Energy Phase Change

I tried using the equation Q'*t= Q1+Q2. Where Q' is the energy of the reactor aka 200,000 kJ and t is the time. Take Q1 to be (1/2m*2257) and Q2 to be (1/2m*4.184*90). The 90 is the change in temperature for the phase change to occur from liquid water to gas, or boiling. Plugged everything in...
9. ### The magnetic phase change of an electromagnetic wave during reflection

If the question had mentioned ##\overrightarrow{E}## instead of ##E_\bot##, then we could have used ##\overrightarrow{B}=\dfrac{1}{v}\widehat{k}\times \overrightarrow{E}## to get the direction of the magnetic field. But the question had only mentioned ##E_\bot##. To my understanding, knowing...
10. ### Confusion about whether to use the specific heat of water or ice

My thought process of how i do the ice melting part: (note I just ignore the copper/lead part cause I already know how to do that part) Q_ice + Q_melt + Q_liquid so, it 0.018(2100)T+0.16(4190)T+0.018(334*10^3) but on chegg they didn't use 2100 but they just use 4190 instead and I am confused...
11. ### What exactly happens during a phase change?

What will happen if say, I have both ice and water inside the refrigerator and I set the fridge to exactly 0 degrees Celsius? Since both melting and freezing happen at 0 degrees, what will happen to my water? what about to my ice? Will they stay the same? I know this is an ignorant question, but...
12. ### Understanding Phase Change: R, L & C

Why do we need to consider phase change? Here are my thoughts: is it because voltages are different in phase for each of the three electrical accessories, R, L and C?
13. ### Engineering Spinodal and Isotherms graph on P-V diagram

Hey guys, During my work I have to show on a P-V diagram certain points on the spinodal for water. How do I draw the spinodel and isothermal lines on a diagram (for example in Excel)? Is it something that I need to calculate? I'm lost on this, I did not find anything relevant on the internet...
14. ### Thermodynamics: phase change and latent heat problem

The second question is where I'm lost. The answer to the first question is 5.39 grams. The second is 10.3 grams. Until I saw the answer I was setting the equation up as if some of the original steam had condensed. But it appears that some of the original water changed into steam. Is it necessary...
15. ### The relationship b/w infrared, temperature, and electron excitation

Homework Statement:: 1. Does the increase in kinetic energy in (for example) water that results from increasing its temperature result from electron excitation (i.e. increasing electron energy levels) or simply increasing their velocity or vibration amplitude/frequency? 2. If excitation is...
16. ### Entropy change when melting ice then refreezing the water

##dmL_f= Q \; \; ##,##∆T=\frac{T(v_l-v_s)∆P}{L} \; \;##,##\frac{dmL_f}{T_0}= dS_2 \; \;##,##\frac{dmL_f}{T_1}= dS_1 ##
17. ### Low-Temp Liquid Helium System: Evaporation Heat & Temperature

We consider a system composed of liquid helium in equilibrium with its vapor at very low temperature T, each phase being considered extensive. We neglect the mass of the gas compared to that of the liquid, as well as the heat capacities of the gas and the walls compared to that of the liquid...
18. ### How is absorbed thermal energy invested during a phase change?

Hello, I was pondering on the well known fact that a certain amount of substance, when absorbing heat, increases in temperature up to a certain temperature and then phase (state) transformation takes place. Any energy supplied at that point does not increase the temperature any further but is...
19. ### Enthelpy vs Internal Energy in Phase Change

Is there anybody who can advise wether the heat lost / gained during vaporisation, is best calculated from enthalpy, or from internal energy, in the steam tables? I am trying to establish the increase in the volume of milk when the temperature is raised by adding saturated steam at 1 bar (1...
20. ### A Which liquids do not supercool?

It seems like having the ability to become supercooled below their melting point is the default for liquids (at least liquids without suspended particles, without many interfaces, and without other perturbations). Are there any liquids that don't supercool at all? Or if not, are there any...
21. ### B Phase change or not: oil in the refrigerator

Cooked some french fries last night using oil saved in the refrigerator. The oil appears to have undergone a phase change, after some time in the refrigerator instead of being a yellowish transparent liquid it was a semi-solid soft whitish non-transparent stuff when I took it out of the...
22. ### Question about Phase Change & Latent Heat

Homework Statement When running, some (heat) energy is lost by the evaporation of sweat. If a runner loses 1.0 MJ( Mega Joules) of energy via sweating, calculate an approximate mass of sweat evaporated from the runner. Homework Equations Q = McΔT Q (Joules) = M (Mass) c (Maximum Heat...
23. ### Thermal physics phase change: Liquid copper to solid

Homework Statement How much energy must be removed from the system to turn liquid copper of mass 1.5kg at 1083 degrees celsius to solid copper at 1000 degrees celsius? a. -2.49X10^5J b. -3.67X10^4J c. 2.25X10^3J d. 9.45X10^4J e. -2.78X10^3J Homework Equations Q=Mc(Tf-Ti)...
24. ### Why does the partial pressure of H2O stay the same

https://ibb.co/dxwnMe https://ibb.co/miNu1e In these slides they show the partial pressure of the H2O gas not changing when the enternal pressure on the entire gas is increased. Why is this the case? I know it condenses to maintain the same partial pressure, but couldn't the partial pressure of...
25. ### How to calculate change in pressure from LN2 phase change

I am trying to calculate the increase in pressure caused by liquid nitrogen when it changes from liquid to vapor within a closed, constant volume at atmospheric pressure. How can this be done? Do I need to include the heat of vaporization?
26. ### Film Thickness for Minimum Reflection of Monochromatic Light: How to Calculate?

Homework Statement Monochromatic light of wavelength, λ is traveling in air. The light then strikes a thin film having an index of refraction n1 that is coating a material having an index of refraction n2. If n2 is larger than n1, what minimum film thickness will result in minimum reflection of...
27. ### If you threw a warm water balloon into space, would it boil?

And by how much would the balloon expand, if at all?
28. ### Does Phase Change on Reflection Violate Stokes Relation?

We know that reflected light undergo a phase shift of π in EXTERNAL REFLECTION but there is no phase shift in INTERNAL REFLECTION . Does this violate Stokes Relation, which states that every reflected beam undergo of phase shift of π ?
29. ### A Phase Change Problems: A Student in Coventry Explores Solutions

Hello, I am a student in Coventry, UK working on Phase Change Problems and going through 1-Phase Neumann Analytical solutions. As per most books, or specifically Mathematical Modeling of Melting and Freezing Processes chapter 2 (attached) page 36, equation 15, the general equation of...
30. ### Liquidification of Helium under constant Enthelphy Condition

Homework Statement a)Helium enters a closed system as a flow of compressed gas at a temperature of 14 K and at pressure p (enthalpy conserved). A fraction α emerges as liquid and the rest as gas at 14 K, both at atmospheric pressure p0. Find an expression for α in terms of the enthalpy H(p) of...
31. ### B Why is the volume of a gas bigger during a phase change

Hello, I would like to know, why is the volume of gas produced during phase change significantly more than the original volume of the liquid being used? Say water changing phase at 1atm.
32. ### Final temperature of the water after adding heat?

Homework Statement You add 1500 cal of heat to a cup of water at 22.5ºC. The water has a mass of 500.0g. What is the final temperature of the water? Homework Equations Q=mcΔT The Attempt at a Solution so i tried solving it by finding the energy of the water Q=(500g)(1.0cal/g)(22.5ºC) Q=11250...
33. H

### How water induces phase change of TiO2 after acid-etching?

It is reported that TiO2 thin surface amorphous layer left after acid-etching with hot HCl-H2SO4 solution slowly changes from the original flat surface to a layer rich in nano-scale features (granules attached to the surface) of 20 ~ 30 nm in size. You can see these nano-features in the picture...
34. ### Phase of refrigerant crossing heat exchanger devices

When a refrigerant crosses a heat exchanger device or has some heat added into it, like condenser/evaporator or boiler/cooling tower, does the phase always change? If that's so, why? Or do we need to check if the temperature is above or under the boiling point?
35. ### What is a distinct phase change?

"At pressures above the critical pressure, there is not a distinct phase change process. Instead, the specific volume of the substance continually increases, and at all times there is only one phase present." What does "distinct phase change" mean here? First to understand this I should...
36. ### Phase shift of e.m. wave through a glass plate

Homework Statement Consider a glass plate of refraction index n and thickness ## \Delta x ## placed between a point monochromatic source S and an observer O, as in picture. (a) Prove that, if absorption from the plate is neglegible, then the effect on the wave received by O is the add of a...
37. ### I Derivation of phase change parameter in dispersive medium

Hi, I'm trying to evaluate the derivates of first, second and third order of the phase change parameter in a dispersive medium. In such medium the refractive index is a function of the wavelength. In my case it depends on the wavelength in vacuum. \begin{equation*} n(\lambda_0 )\end{equation*}...
38. ### Change in internal energy during water vaporization

According to the first law of thermodynamics, dQ = dU + dW and you can find dU = nCvdT If this is the case then when water at 100°C vaporizes to steam at 100°C shouldn't the change in internal energy be zero because it is dependent on temperature change?
39. ### Phase Change in a transmission line

Homework Statement (a) A transmission line has a length, ##l##, of 0.4λ. Determine the phase change, ##\beta l##, that occurs down the line. Homework Equations ##\beta=\frac{\omega}{f\lambda}## or ##\beta=\frac{2\pi}{\lambda}## The Attempt at a Solution This question was posted a couple of...
40. ### Equilibrium temperature of some ice and steam

Homework Statement "A well-insulated bucket of negligible heat capacity contains 120 g of ice at 0°C. If 20 g of steam at 100°C is injected into the bucket, what is the final equilibrium temperature of the system?" Homework Equations $$Q_{fus} = m_{water}L_{fus}$$ Q_{vap} =...
41. ### How to calculate time to change the temperature of metal

So I'm looking to calculate the time required to raise the temperature of a piece of lead. What I know so far: Mass of metal: 4 grams Initial temperature: 250 degrees Celsius Final temperature: 350 degrees Celsius Specific heat of lead: 0.13 kj/kg I'm very new to thermodynamics and don't know if...
42. ### Propane phase change in a container

If I had a container containing 10 bara of nitrogen, and pumped in liquid propane at room temperature would the propane boil? If I carried out the same experiment but this time at 5 bara, what would be the temperature of the material once the propane had completed its phase change i.e would it...
43. ### What will be the equilibrium state in the liquid N2 chamber?

Suppose there is a test chamber containing liquid nitrogen. The container is insulated and only a small opening is there so that chamber is exposed to atmospheric condition. As the saturation temperature of liquid nitrogen is -196 degree Celsius at 1 atm pressure. chamber will remain at -196...
44. ### Quantity of heat, phase change of ice to water

Homework Statement A 1x106 kg piece of ice is placed into a lake. How much heat is taken from the lake to raise the temperature of the ice from 0 °C to 1x10-20 °C? How much volume does the lake increase by? Latent heat for water is 334x103 J/kg Homework Equations Found in my textbook, cice =...
45. ### B Why do water waves not undergo a phase change when they hit a fixed wall?

Why won't water wave undergo a phase change of pi when it propagates to a fixed wall just like a pulse of string does.
46. ### Phase change material steady melt temp, like ice water?

Ice melting in a box has the water coming off it at a temp just above freezing until all the ice is gone. Are all phase change materials pretty much the same, with their immediate containment container exterior staying pretty much just above their phase change temp until all the PCM inside has...
47. ### Entropy Change in a Reversible Process multiple phase change

Homework Statement (a)How much heat must be added to a block of 0.120kg of frozen ammonia initially at 100oC to convert it to a gas at 80oC given the following information? (b) assuming this could be done using a reversible process what would be the total entropy change associated with this...
48. ### Simulation of phase change materials

Dear all, Interested in change phase, I would like to set a simulation to understand the multiphysics phenomena of heat storage in a shell and tube tank between hot water as the heat transfer fluid and a PCM ( phase change material) using the commercial CFD software Fluent. The purpose is to...
49. ### Phase change phenomena in Fluent v15

Hello everyone, I am beginner in fluent v15, and I want to simulate the temperature change as a function of time in the phase change materials "PCM" and the heat thermal fluid "HTF" and the PCM fusion Front. Regarding the geometry I chose to work with two coaxial tubes: the inner tube contains...
50. ### Grade 11 Thermodynamics Question

Homework Statement You add 50 g of steam at 150 degrees centigrade to 50 g of ice at negative five degrees centigrade. What is the final temperature? Homework Equations Q = mLfv Q = mcΔT The Attempt at a Solution Qg = Ql Q1 + Q2 = -Q3 - Q4 mLf + mcΔT = -mLv + mcΔT [ΔT will be negative, making...