What is Phase change: Definition and 142 Discussions

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. M

    What is the reason for phase change of light on reflection from a denser medium?

    What is the explanation for the phase change of pie that occurs when a light ray gets reflected from an optically denser medium? This fact was demonstrated by the Llyod's mirror experiment, but what is the theoretical explanation for it? Thanks
  2. S

    Heat exchange involving phase change, hot iron into water ->steam,

    Homework Statement I have been working on a University Physics thermodynamics problem for over a week now, day and night. I've consulted two physics PhDs, posted on Yahoo Answers (nobody took the bait) and I'm still stuck. I just wasted an hour and a half carefully posting my problem and...
  3. S

    How Do You Calculate Energy Changes in Water Phase Transitions?

    Homework Statement 1. What amount of energy is released whan 10g of steam at 100 degrees C condenses and then cools to water at 0 degrees C? 2. 1840 calories of heat is added to a 300g block of ice at 0 degrees C. what amount of ice melts? 3. 3600 calories of heat is removed from 5g of...
  4. C

    Total heat removed from phase change

    Ethyl alcohol has a boiling point of 78.0°C, a freezing point of -114°C, a heat of vaporization of 879 kJ/kg, a heat of fusion of 109 kJ/kg, and specific heat of 2.43 kJ/(kg · K). How much energy must be removed from 0.584 kg of ethyl alcohol that is initially a gas at 78.0°C so that it becomes...
  5. W

    Sudden Phase change of water to ice

    "Sudden" Phase change of water to ice Last winter, I had a store-bought bottle of water I took snow camping. The closed bottle of water sat in the snow overnight. The next morning the water was still liquid, when I opened the bottle, I heard the hiss from the release of pressure on the bottle...
  6. D

    Solving Phase Change Question: What is the specific heat?

    We have a tricky question for homework that is starting our new unit of phase changes, after we have been doing calorimetry 120.0g of an unknown solid at 235*c is added to a 1.5kg piece of ice at -20*c inside a styrofoam container. After a period of time, both substances areat 120*c. What is...
  7. L

    Phase change Melting ice with hot tea.

    Homework Statement 175 cm3 of hot tea at 87°C are poured into a very thin paper cup with 80 g of crushed ice at 0°C. Calculate the final temperature of the "ice tea". (Hint: think about two processes: melting the ice into liquid and, maybe, warming the liquid.) Homework Equations...
  8. K

    What's the actually meaning of phase change?

    In fundamental optics, we know that "There is no phase change when the wave is reflected from a boundary leading to a medium of lower index of refraction" So, does it mean if a light is incident on a 100% reflected mirror, it will induce a phase change? If there is a phase change, why we...
  9. G

    Wave of phase change (MOVIE: Hot ice how-to)

    Hot ice solidifies instantaneously when its cold... http://www.youtube.com/v/aC-KOYQsIvU Are there really any oscillations or waves of different states (alternating states) in materials? Perhaps gradient of heat or a bump of pressure spreading? Sound? Electricity?
  10. H

    Wave Velocity, Amplitude & Phase change

    Hi All, I am having trouble trying to understand & calculate the effects that magnetic soils have on a pulsed induction metal detector, in particular soils containing iron. I have read this: The section on Soil Magnetic Properties...
  11. F

    How much pressure does water have to be in for it to phase change

    I was wondering if it was possible to put water in a tube, and either add air pressure or put it in a vacuum and changee it's phase change? I herd at wikipediea that you can change the state of matter somthing is in by either changing the tempature or pressure that it's in.
  12. F

    Physics Problem about Heat Phase Change

    1. How many grams of ice at 0 degree Celsius must be added to 350.0 grams of water at 80.0 degree Celsius contained in an aluminum calorimeter whose mass is 150.0 grams in order to cool down the water to 30.0 degree Celsius? [Specific heat of aluminum: 910 J/kg] [Latent heat of vaporization of...
  13. H

    Phase Change of \pi: Exploring Reflection and Non-Reflective Coatings

    Hi, When exactly does the phase change of \pi occur when a EM wave reflects from a surface? I notice that it happens in Lloyd's mirror for example, and also when considering non reflective coatings on lenses. Is it just when the EM wave is going into a medium with higher refractive index or...
  14. J

    Latent Heat Problem/ Phase Change .

    Latent Heat Problem/ Phase Change...Please Help! At 1:00pm you place an ice cube tray in the freezer. Each of the 12 1-gram cubes has a temperature of 20°C. At 1:10 the water temperature has dropped to 12°C. At what time will you have ice? i have been messing around with this problem for...
  15. J

    Calorimetry and Phase change question

    The question is: An insulated beaker with negligible mass contains liquid water with a mass of 0.225 kg and a temperature of 75.8 C. How much ice at a temperature of -23.6 C must be dropped into the water so that the final temperature of the system will be 31.0 C? Take the specific heat of...
  16. F

    The Physics Behind CPU Cooling with LN2 or Phase Change

    Hello everybody, my question is: do you get an increase in speed/power/performance when you "freeze" computer components such as the CPU with LN2 or phase change cooling, getting to under -100º,-150º. Because as long as I'm aware CPU´s are made out of semiconductors and as temp lowers the...
  17. N

    Phase Change & Temperature: What's the Difference?

    "When a substance absorbs or releases heat, one of two things can happen: either its temperature changes or it will undergo a phase change but not both at the same time" Can someone clarify this statement? During a phase change, isn't what's going on really just increasing the kinetic energy...
  18. M

    Phase Change at reflection:

    Homework Statement Part of a longer question, what is the phase change, if any for a system of three substances of different n where there is surface reflection between n1 and n_f which is meant to constructively interfere with another surface reflection between n_f and n3.where n1 < n_f >...
  19. N

    Final Temperature After Phase Change

    Homework Statement find the final temperature of A 150g (0,15kg) cube of ice at 0.0 degrees Celsius is added to 300g(0.3 kg) of water at 50.0 degrees Celsius. Specific heat capacity of ice: 2.09 x 10^3 J/(kg x degrees Celsius) Specific heat capacity of water: 4.186 x 10^3 J/(kg x...
  20. K

    Phase Change Diagram: Solved & Explained

    [SOLVED] Phase change diagram Now that I think about it, this might be more of a chemistry question, but it's for the class "General Physics 1" so go figure :) Homework Statement A container holds 0.550 kg of ice at -15.0 *C. The mass of the container can be ignored. Heat is supplied to...
  21. D

    Ceramic Superconductivity Experiment: Calculating Liquid Nitrogen Boiling Loss

    Homework Statement Some ceramic materials will become superconducting if immersed in liquid nitrogent. In an experiment, a 0.150kg block piece of such material at 20C is placed in liquid nitrogent at its boiling poitn to cool in a perfectly insulated flask, whcih allows the gaseous N2...
  22. P

    Phase change of reflected wave

    what do we mean when we say that light wave suffers a phase change of \pi when it gets reflected and why does that happen
  23. S

    Heat and Phase change: latent heat

    Homework Statement A woman finds the front windshield of her car covered with ice at -12.8°C. The ice has a thickness of 4.60 10-4 m, and the windshield has an area of 1.25 m2. The density of ice is 917 kg/m3. How much heat is required to melt the ice? Homework Equations Q=mL or change...
  24. W

    Final Temperature After Phase Change and Transfer of Energy

    Homework Statement A 0.011 kg cube of ice at 0.0 degrees Celsius is added to 0.450 kg of soup at 80.0 degrees Celsius. Assuming that the soup has the same specific heat capacity as water, find the final temperature of the soup after the ice has melted. (Hint: There is a temperature change...
  25. C

    How many ice cubes were added to cool the pool to 17°C?

    Homework Statement Trying to beat the heat of summer, a physics grad student went to the local toy store and purchased a child's plastic swimming pool. Upon returning home, he filled it with 156 liters of water at 26°C. Realizing that the water would probably not be cool enough, he threw ice...
  26. M

    Looking for Phase change material

    Hi All, I'm working on a project that requires a flexible membrane be heated and cooled about 2000 times. During the cooling process, I require the material give off heat for as long a period of time as possible. I figure a phase change material will have the highest heat capacity and give...
  27. M

    Best Phase Change Materials for Flexible Heating/Cooling Membrane

    Hi All, I'm working on a project that requires a flexible membrane be heated and cooled about 2000 times. During the cooling process, I require the material give off heat for as long a period of time as possible. I figure a phase change material will have the highest heat capacity and give...
  28. L

    Proof of Phase Change: How Can We Prove It?

    how can we proof the phase change from denser spring to a less dense one?
  29. G

    Are degrees of freedom in a molecule affected by phase change?

    For a molecule of water, I understand that there are 6 degrees of freedom for each of the three atoms within it; 3 translational and 3 due to the potential energy of the bonds. Is this at all affected when the water goes from solid to liquid or gas?
  30. G

    Calculating Final Temperature of Phase Change Using Heat Absorption

    1. A 10-kg block of ice has a temperature of -10°C. The pressure is one atmosphere. The block absorbs 4.12E6J of heat. What is the final temperature of the liquid water? 2. Q = mL and Q = cm/\T 3. I tried doing Q = cmT and plugging in the values above to get 88.4 degrees as the...
  31. A

    Thermal Energy storage of phase change material

    Hi all you braniacs out there... I am a final year mechanical engineering student. I need to do a final year project on numerical simulation on melting of phase change material.. I will be required to make use of gambit and fluent CFD software of which i have no idea about... However currently...
  32. P

    Is the CERN particle accelerator risking a phase change in the Universe?

    Phase Change of the Universe?? I was listening to Coast to Coast radio this morning on the way to work and they had some scientist on who was saying that the when the CERN particle accelerator is turned on in November 2007 one of its main goals is to find the Higgs Boson particle. However...
  33. S

    Lunar Phase Change with Reversed Moon Orbit

    hey guys could anyone help me with this q? q)how would the timing and sequence of lunar phase change if the moon moved at the same speed around its orbit but in a different direction? i thought it would simply reverse the phases of the moon, but I think the answer needs to be more detailed...
  34. D

    What is the final temperature and amount of material and water in each state?

    I am working on a proble with this basic set up: 500g of some material starts at -22'C in a 400g container. 90g of steam (water) starts at 120'C and is mixed with the unknown material. Find the final temp. and amount of material and water in each state. Unkown c(solid) = 0.4 cal/g'c...
  35. D

    Stuck on this phase change question

    I have a question on dropping ice (-10 celsius) into water (20 celsius). What is the final temp? i have used Q = m.c.delta T between -10 and 0 I know i have to use Q = m.l for the phase change and then agian use Q = m.c. delta T to find a final temp. How do i relate these two...
  36. B

    Phase Change: What is actually going on?

    When water changes phase from liquid to gas, what is actually happening at a molecular level? I have heard the general explanation that enough kinetic energy is imparted to the surface water molecules to allow them to "breaK" free from the dipole forces that hold them in the liquid. Sort...
  37. D

    How do I calculate the final temperature when dropping ice into water?

    I have a question about droping ice into water and working out the final temp. ice is -10 and water is 20 degrees c, I know that from -10 to 0 I can use, Q = m.c.delta theta but does this give me the final answer or do i need to use, Q = m.l, after 0. I think this because this...
  38. A

    How Does Phase Change Affect Destructive Interference in Radio Waves?

    Hmm, more questions on phase change. I was looking at this question: "Waves from a radio station have a wavelength of 319 m. They travel by two paths to a home receiver 14.2 km from the transmitter. One path is a direct path, and the other is by reflection from a mountain directly behind...
  39. D

    Calculating S & G for Phase Change of Water

    phase change? How do I calculate the values of change in entropy (S) and change in Gibbs free energy (G) for the conversion of n=1 mol of liquid water at 100 C and 1 bar pressure into vapor at the same temperatue and a pressure of 0.1 bar. Assume ideal behavior for the vapor. the molar enthalpy...
  40. L

    Final Temp of Water in Calorimeter After Heating Silver Ring

    A 25.5 gram silver ring ( c=234 J/kg * c) is heated to a temperature of 84 degrees C and then placed in a calorimeter containing 0.05 kg of water at 24 degrees C. The calorimeter is not perfectly insulated and .140 kJ of energy is transferred to the surrounding before a final temperature is...
  41. R

    Q: Transparency in phase change alloys

    Hi, I was wondering if anyone could explain the following: The technology behind CD-RW discs relies upon phase change alloys usually comprising of indium, silver, tellurium, and antimony. These are translucent in their crystalline state but opaque in their amorphous state. I understand why...
  42. turin

    Understanding Phase Change Hysteresis: A Comprehensive Guide

    Does phase change have hysteresis?
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