What is Latent heat: Definition and 206 Discussions

Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process — usually a first-order phase transition.
Latent heat can be understood as energy in hidden form which is supplied or extracted to change the state of a substance without changing its temperature. Examples are latent heat of fusion and latent heat of vaporization involved in phase changes, i.e. a substance condensing or vaporizing at a specified temperature and pressure.The term was introduced around 1762 by British chemist Joseph Black. It is derived from the Latin latere (to lie hidden). Black used the term in the context of calorimetry where a heat transfer caused a volume change in a body while its temperature was constant.
In contrast to latent heat, sensible heat is energy transferred as heat, with a resultant temperature change in a body.

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  1. P

    How Long Will Snow Last with Limited Solar Heat?

    Homework Statement When spring finally arrives in the mountains, the snow pack may be two meters deep, composed of 50 % ice and 50 % air. Direct sunlight provides about 1000 wats /m^2 to Earth's surface, but the snow might reflect 90 % of this energy. Estimate how many weeks the snow pack...
  2. K

    Calculate Latent Heat: L = (S_after - S_before)T

    We could use the change of entropy before and after eh phase changed to calculate the latent heat L = (S_{after} - S_{before})T and in some case, if we know the relation of pressure and temperature, we can also apply Clausius-Clapeyron relation to calculate the latent heat. I...
  3. T

    Specific Heat and Maybe Latent Heat also

    Homework Statement Several small piece of aluminum, having total (combined) mass of 2.5 kg are placed in liquid nitrogen and, when removed, are at a temperature of -135C. The aluminum is transferred to an insulating container with 0.50 kg of water. The water is at 25.0C [ Ignore heat lost from...
  4. J

    Latent heat of fusion/latent heat of vaporization

    Homework Statement see attachment Homework Equations The Attempt at a Solution I think I would divide the approximate slope from the beggining by the approximate slope at the end but I'm not sure if that is correct. Also, I do not know how to come up with a number answer.
  5. J

    What Is the Correct Value for k in the Latent Heat Equation?

    I have a derived equation for latent heat, L = kIV∆T/∆M. I was just wondering what the value for k is. I have it written down in my notebook but i can't tell if i wrote a 2 or a 7, so it should be .239 or .739. If anyone knows it'd be appreciated, thanks.
  6. 9

    Specific Latent Heat of Fusion problem

    Homework Statement An ice tray containing 200 g of water at 25 degrees celecius is placed in the freezer. How much heat energy has to be removed to change the water into ice at -4 degrees celcius? Homework Equations Q= mc(Tf-Ti) + MLf + mc(Tf-Ti) The Attempt at a Solution I know...
  7. S

    Pizza: Latent Heat & Burning Tongue

    Consider a hot pizza from the oven. Why do you tend to burn your tongue on the cheese, but not the crust?
  8. 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...
  9. B

    Specific latent heat of fusion lab

    Homework Statement It's part of a lab designed to find the specific latent heat of fusion of ice using the method of mixtures. The results are in the 1st attachment..I want to find the specific latent heat of fusion of ice from those nos.Homework Equations heat lost by water = heat gained by...
  10. B

    Experiment for specific latent heat of fusion of ice

    i need some help guys. see, i was doing my school-based assessment labs probably two months ago and as i was going to write up the report I lost my procedure of how to do the experiment. In the one I did, we didn't use any calorimeter like how they describe it when you google the experiment...
  11. A

    Melting Lead in a Kiln: Calculating Time and Energy Requirements

    Homework Statement A sculptor has come to you with a problem, because she knows that you are such a good physics student. She wishes to make a lead casting of an object which will require 2 kg of melted lead. If the lead was stored in her basement at approximately 55˚F, and it is to be...
  12. C

    Calculating the Final Equilibrium Temperature with Latent Heat and Phase Changes

    Homework Statement 25 kg of ice at 0C is combined with 4 kg of steam at 100C. What is the final equilibrium temperature in Celsius of the system? (Lf = 3.33x 10^5 J/kg; Lv= 2.26x10^6 J/kg; 1 cal= 4.186 J) Answer: 20 Homework Equations mc(Tf- Ti) m(Lf) or m (Li) The Attempt at a...
  13. C

    Specific and Latent Heat - Pre-laboratory work

    I just need any of you to check if I've answered the problems correctly, thanks. Homework Statement Question 1. A student uses some equipment that can add energy at a constant rate to some water contained in a copper calorimeter can. To keep the temperature of the water uniform, the...
  14. C

    How Does Latent Heat Affect Ice Melting in an Insulated System?

    Homework Statement In an insulated vessel, 250 g of ice at 0 °C is added to 600 g of water at 18 °C. (a) What is the final temperature of the system? (b) How much ice remains when the system reaches equilibrium? Homework Equations The Attempt at a Solution If I'm not mistaken...
  15. T

    Latent heat, steam and ice question

    [SOLVED] Latent heat, steam and ice question Homework Statement 14g of steam at 100C is added to 47g of ice at 0.0 degrees C. a) Find the amount of ice melted and the final temperature. Homework Equations Q=mL Q=mc\DeltaT Q(hot)=-Q(cold) The Attempt at a Solution Ordinarily, in...
  16. S

    Determine the specific latent heat of vaporization of water

    Homework Statement from the following observations made during an experiment,determine the specific latent heat of vaporisation of water. initial mass of water 400g final mass of water 450g mass of calorimeter 200g initial temperature of water & calorimeter 16 degrees final temperature...
  17. C

    Changes of state and latent heat

    Homework Statement A 0.2 kg block of ice at -15*C is placed into a pan on a stove, heated to a liquid, and then to vapour with a final temperature of 115*C. Calculate the total amount of heat required for this process. Homework Equations Eh = mc(t2 - t1) Lf (or Lv) = Eh / m The...
  18. S

    Calculating Latent Heat of Water Vaporization

    Homework Statement from the following observations made during an experiment, determine the specific latent heat of vaporisation of water. initial mass of water 400g, final mass of water 450g (the extra is condensed steam) mass of calorimeter 200g, initial temp of water & calorimeter...
  19. G

    How can I solve Latent Heat Problems with detailed explanations?

    Latent Heat Problems ! Help I have 2 questions that I need help on. All help will be very appreciated. 1. A cube of ice is taken from the freezer at -8.5 C and placed in a 95grams aluminum calorimeter filled with 310g of water at toom temperature of 20 C. The final situation is observed to...
  20. E

    How Much Steam Is Needed to Melt Ice into Water at 20 Celsius?

    Homework Statement What mass of steam at 100 Celcius must be added to 1.00 kg of ice at 0 Celcius to yield liquid water at 20 Celcius. Homework Equations Q = mL Q = mc(deltaT) change in energy = 0 The Attempt at a Solution Ice m= 1.00 c = 2100 T1 = 0 Tf = L = 333...
  21. G

    Latent Heat: 180kcal Lost in 30 Min, How Much Water?

    The question reads: During exercise a person may give off 180kcal of heat in 30 min by evapouration of water from the skin. How much water is lost? If someone could clearly explain the question that would be great thanks
  22. S

    Calculating Latent Heat of Steam: Mass, Temp & Thermal Capacity

    Homework Statement Ive been tasked with working out the Latent heat of steam the following are all my results and values used. Mass of the calorimeter and stirrer: 0.068Kg Thermal Capacity of the Calorimeter and Stirrer : 25.772 JK-1 Mass of water and Calorimeter and stirrer: 0.145Kg...
  23. M

    Find the latent heat of vaporization

    Simple Q - Latent Heat of vaporization H20 @15 C and 115 C sorry , I have reposted in the homework help section... I am not good a math and physics and I am taking a intro Food Engineering course. My question on my assignment states " Find the latent heat of vaporization for water at 15 °C...
  24. T

    Latent Heat of Zinc Sublimation at 600K

    The Latent Heat of sublimation for zinc(atomic mass = 65.4 u) at 600k is 1,990,000 j/kg. Assume that the zinc vapor can be treated as a monatomic ideal gas and that the volume of one kilogram of solid is negligible compared to that of the vapor. What percentage of the latent heat serves to...
  25. D

    Temperature dependence of a latent heat.

    Homework Statement You Need to find the enthalpy of sublimation of solid A at 300K. The following equilibrium vapor pressure measurements have been made of pure A : (1) At 250K, the pressure is 0.258 bar and (2) At 350K, the pressure is 2.00 bar. The following heat capacity data is known...
  26. F

    Latent Heat: Calculating Final State of Ice/Steam Mix

    Homework Statement Determine the final state when 20 g of 0 degree C ice and 10 g of 100 degree C steam are mixed together in an insulated container Homework Equations Q=mc(delta)T Q=mL (L = latent heat) The Attempt at a Solution So, I know that I should set the heat change in...
  27. R

    Specific heat and latent heat of fusion

    Hi this is my first post and I'm stumped on my last HW problem, so I'm open to suggestions or solutions. 1. A jar of tea is placed in sunlight until it reaches an equilibrium temperature of 35°C. In an attempt to cool the liquid, which has a mass of 220 g, 112 g of ice at 0.0°C is added. At...
  28. D

    HELP Melting Iceberg: Latent heat of fusion

    URGENT HELP! Melting Iceberg: Latent heat of fusion Homework Statement Icebergs in the North Atlantic present hazards to shipping, causing the length of shipping routes to increase by about 30 percent during the iceberg season. Attempts to destroy icebergs include planting explosives...
  29. J

    Specific heat, latent heat, and temp

    The system, originally at T_A = 21.0 Celsius, is placed in a freezer, where energy is removed from it in the form of heat at a constant rate. The figure shows how the temperature of the system takes t_1 = 10 min = 600 s to drop to 0 Celsius, after which the water freezes. Once the freezing is...
  30. S

    Calculating Energy Required to Heat and Change State of Ice in an Oven

    A student takes 0.45kg of ice. The ice is initally at -23'C. She heats the sample in an oven until the temp is 134'C. a). What is the Q needed to heat the ice to its melting point? b). What is the Q needed to change the solid ice into liquid water? c). What is the Q needed to heat the liquid...
  31. S

    How Much Energy Does It Take to Heat Ice to Steam?

    A student takes 0.45kg of ice. The ice is initally at -23'C. She heats the sample in an oven until the temp is 134'C. a). What is the NRG needed to heat the ice to its melting point? b). What is the NRG needed to change the solid ice into liquid water? c). What is the NRG needed to heat the...
  32. X

    Specific Latent Heat of Fusion

    Homework Statement need to work out the Specific Latent Heat of Fusion i did the experiment and here are the results Results: Mass of calorimeter Mcal 116.87g Mass of H2O MH2O = [Mcal + H2O] - Mcal 80.82g (197.69g) Mass of Ice Mice = [Mcal + Mice + H2O] - MH2O 12.58g (210.27g) Room...
  33. D

    Determine the latent heat of an unknown substance

    I need to determine the latent heat of an unknown substance X in kcal/g if 3.0g of boiling liquid X are completely vaporized in 1.5 hours by an energy source of 10kcal/hr. Thanks a million! Dave
  34. N

    How Much Heat to Turn Ice at -10°C into Water at 20°C?

    Homework Statement How much heat is necessary to change 395 g of ice at -10°C to water at 20°C? Homework Equations mLf + mc(delta)T The Attempt at a Solution (.395kg)(80kcal/kg)+(.395kg)(1.00kcal/kg x 1 deg C)(20--10) (31.6kcal)+(.395kcal degC)(30) 31.6kcal + 11.85 kcal=43.45...
  35. 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...
  36. 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...
  37. M

    Specific heat capacity and latent heat of fusion

    help! need help here because my answers are different from the answer on the book. just wanted to make sure that i am right. these are the problems: 1. How much heat is needed tor aise the temperature by 10 deg celsius of 5 kg og a substance of specific heat capacity 300J/kg deg celsius? what...
  38. F

    Temp equilibrium / latent heat

    Homework Statement 1 625g iron block is heared to 352 C is placed in an insulate container (of negligible heat capacity) containing 40g of water at 15 C. what is the equilibrium temp of this system? if your answer is 100 C, determine the amount of water that has vaporized. Homework...
  39. M

    Latent Heat and final temperature

    Homework Statement Steam at 100°C is injected into 1.8 kg of water at 22°C in a well-insulated container, where it condenses and mixes with the existing water, reaching thermal equilibrium. If the final temperature of the well-mixed water is 25°C, what is the mass of the injected steam...
  40. B

    Need some clarification for a latent heat related problem

    Ok, I don't really need to know because it's something I've been told to ignore in the text, but I'm curious about it anyway, here goes: At a nuclear power plant, water at 8 deg. celsius from a nearby lake is used in a heat exchanger to condense spent steam, at a temperature of 120 deg...
  41. dav2008

    Determining binding energy from latent heat of vaporization

    The measured value of the latent heat of vaporization of argon (at 1 atm) is 6.43 kJ/mol. Use this to estimate the binding energy. (Given answer: 0.059 eV) [Boiling point @ 1atm: 87.3K] My initial approach was that since 6,430 joules worth of bonds had to be broken for a mole of Argon to...
  42. P

    Calculating the Heat Required to Melt Lead from 25 oC to 328 oC

    Am I on the right track here? How much energy is required to melt 400 grams of lead, if the initial temperature is 25 oC? m=0.4kg deltaT 328-25= 303 SpecHeat = 128 Q=mCdeltaT Q=.4*128*303 15513.6J
  43. E

    Specific and latent heat question

    Steam at 100 degrees Celsius is bubbled into 250 cm3 of water at room temperature in a calorimeter cup. How much steam will have been added when the water in the cup is at 60 degrees Celsius? (Ignore the effect of the cup.) So I did: -(Heat lost by steam) = Heat gained by water msteamLvap...
  44. G

    Solving Latent Heat and Thermodynamics Problems: Explained for 9th Graders

    how do you slove latent heat problems? also is there a easier way to slove thermodyamics problem? explain in a way a way that a 9th grader like me can understand. thanks
  45. L

    Indirect ways to estimate latent heat of fusion?

    Hello. Often high temperature data are not available. I am missing the melting heat of many coumpounds. However, rather precise binary phase diagrams are available. (my examples deal with silicates, say CaO-SiO2 for example, http://www.npl.co.uk/mtdata/demo/dgox1.html) I would like to...
  46. P

    How Much Ice Melts When a Skater Stops?

    A 58.0 kg ice-skater moving at 6.25 m/s glides to a stop. Assuming the ice is at 0°C and that 53.5 percent of the heat generated by friction is absorbed by the ice, how much ice melts? Should I first calculate the work? I know I need to use Delta U= Q-W...but what is Delta U in this case?
  47. M

    Calculating Heat Requirements for Phase Changes

    I have no clue how to do this? Which would require more heat, melting 500 g of 0 C ice or turning 500 g of 100 C water into steam?
  48. S

    Change of Phase and Latent Heat

    I am trying to word this question as best as I can. Once water has reached its bottom-notch state/position, will the temperature increase? I mean, if water changes to steam once heat is added, why won't the temp. increase (or stay constant)? Another question is why won't the temp. rise...
  49. J

    Calculate Latent Heat of Steam to Ice Transformation

    I have to change steam at 110C and end up with water frozen into ice at 0.c . How much heat will be removed? How do I go about changing this to steam, liquid, solid? Do I use mLf+mcdeltaT each time?
  50. K

    Latent Heat of Fusion | Physics Explained

    Please see the attached Word file.
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