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. F

    How Much Heat is Needed to Vaporize Ethyl Alcohol from -50°C to Boiling Point?

    Homework Statement How much heat is required to change 1.75 L of Ethyl Alcohol (C2H6O) at -50.0°C to a gas at its boiling point? Ethyl Alcohol V = 1.75 L Ti = -50°C 46 g/mol density = 0.789 g/cm3 boiling point = 78°C specific heat (c)= 2400 J/kg*C° Heat of Vaporization (Lv) =...
  2. W

    Latent Heat of Vaporization /w Temperature

    Hi, I would like to ask, why is it that the specific latent heat of vaporization of water at, say 10 degrees Celsius, is considerably higher that at 100 degrees Celsius? It would be great if you could provide an explanation from the molecular view. Thanks.
  3. P

    Specific Heat of Nickel / Latent Heat of Fusion

    Homework Statement I've done 2 experiments, one was to find the specific heat of nickel and the other was to find the latent heat of fusion. For the nickel experiment, it involves heating the nickel in a test tube in a water bath, and then transferring the pellets to a Styrofoam cup. With...
  4. J

    Latent heat of vaporization & pressure

    I'm making my way through some workbooks at my job (coal-fired power plant) and I've hit a stumbling block. I could just memorize what the books says, but I really want to understand, so here goes... One question states: "As the pressure exerted on a steam/water mixture increases, (answer...
  5. Telemachus

    Latent heat and Clapeyron equation

    Homework Statement Here there is another problem from callen which I couldn't finish. It says: It is found that a certain liquid boils at a temperature of 95ºC at the top of a hill, whereas it boils at a temperature of 105º at the bottom. The latent heat is 1000cal/mole. What is the...
  6. B

    Where Does the Energy Go When a Ball Becomes Embedded?

    Ive got this question but i don't know how to answer it. A steam boiler produces steam at a rate of 0.5 kg.s-1. If the specific latent heat of vaporisation of water is 2.3 MJ kg-1: (a) What power is consumed to achieve this rate? cheers
  7. S

    How Does Adding Ice Affect the Final Temperature of Hot Coffee?

    Homework Statement A thermos contains 160 cm^3 of coffee at 82.7 °C. To cool the coffee, you drop two 10.0-g ice cubes into the thermos. The ice cubes are initially at 0 °C and melt completely. What is the final temperature of the coffee in degrees Celsius? Treat the coffee as if it were...
  8. P

    Specific Latent Heat and Thermal Physics

    Hi :smile: The mass of liquid nitrogen in an open beaker is found to have decreased by 46.3 g in 10 minutes. If the s.l.h of vaporisation of nitrogen at its boiling point is 1.99 x 105, at what rate were the surroundings heating the beaker? Why is the heat capacity of the beaker irrelevant...
  9. P

    Specific Latent Heat of Vaporization vs Evaporation

    Hi, When studying and thinking about the concept of Specific Latent Heat of Vaporization I keep falling in the trap of confusing it with evaporation - in the end, in both cases water in the liquid state is being changed into vapor. Could anyone help me differentiate the two ideas...
  10. B

    Exploring Latent Heat: A Quantum Perspective

    Hello again my dearest forum <3 I am supposed to learn thermodynamics, but all in all, books here cover only so much of a specific topic. I stumbled upon this term Latent heat. I kinda understand what it is. Its related to phase changes of matter. But is there a quantum background...
  11. D

    Solve Latent Heat Problem: Mass of Injected Steam

    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...
  12. M

    How Does Water Content in Ice Affect Its Latent Heat of Fusion Value?

    We did a calorimeter experiment in my school however the teacher warned us that the latent heat of fusion of ice value will be different from the standard value because the ice has water in it and because the ice melts little before actually doing the experiment. However my question is which way...
  13. A

    Calculate the mass of ice with heat transfer / latent heat

    Homework Statement Find mi, the initial mass of ice. Ti = -20 ci = 2093Jkg-1K-1 Ts = +35 ms = 2kg cs = 837.4Jkg-1K-1 cw = 4187Jkg-1K-1 lf = 3.35x105Jkg-1 S = solid W = water I = ice lf = latent heat of fusion of ice / waterHomework Equations Q=mc\DeltaT Q=C\DeltaT Q=mlThe Attempt at a...
  14. M

    Calculating Latent Heat of Ice: A Physics Practical Guide

    Homework Statement Hi, I've been given the following information to manipulate the results of my last physics practical: Mass Of Water * Specific Heat Capacity of Water * Change in Temperature of Water = Latent Heat of Ice * Mass of Ice + Mass of Ice * Specific Heat Capacity of Water *...
  15. V

    Latent Heat of Fusion and Potential Energy

    I was looking over an old qualifying exam and I came across a problem asking what the maximum height of a mountain on Earth could be. The solution states that the rock at the base of the mountain will melt and flow away when the potential energy of the top layer of the mountain is equal to the...
  16. N

    Calculating Melting Time for 7.5g Ice Cube at 0°C

    An ice-cube has a mass of 7.50 g. The ice-cube is at 0 °C. Heat from the surroundings reaches the ice-cube at an average rate of 1.25 J / s. How long does it take for all of the ice to melt? (specific latent heat of fusion of ice = 333 J / g) A 35.5 s B 55.5 s C 2000 s D 3120 s
  17. S

    Specific heat and possibly latent heat too..

    Homework Statement 0.5kg of ice at 0 degrees celcius is mixed with 0.1kg of steam at 100 degrees celcius. what will be the final temperature? Homework Equations delta Q= m*c*delta T and at first i thought delta Q= m*Lf ,but then i changed my mind. . . The Attempt at a Solution...
  18. S

    Changes of state and latent heat

    Homework Statement A foundry operator finds that it takes 55.6 MJ of heat to heat a 286 kg mass of an alloy steel from 22 degrees C to 452 degrees C. Specific heat capacity of the steel is 452J/kg/K. If the foundry worker cools the steel by poring water onto it, the water will heat up to its...
  19. N

    Is a New Liquid with Lower Latent Heat More Convenient for Boiling Eggs?

    Homework Statement A new liquid is discovered that has the same boiling point and specific heat as water but a latent heat of vaporization of 10 calories per gram. Assuming that this new liquid is safe to drink, would it be more or less convient than water for boiling eggs? Why? The...
  20. P

    Latent Heat and Clapeyron Equation Manipulation

    Hi, I just want to double check if the following is valid. However, I would just like to give you the context of my questions. Basically, I am passing a wire through ice, then I'm trying to figure out how an increase in mass (therefore force) affects the velocity at which the wire goes...
  21. M

    Latent heat and phase change question

    Homework Statement A 100g cube of ice at 0 degrees is dropped into 1.0kg of water that was originally at 80 degrees. What is the final temperature of the water after the ice has melted? Homework Equations Q = ml Q = mc(Tf - Ti) The Attempt at a Solution i'm not sure again about...
  22. G

    Specific Heat Capacity and Specific Latent Heat

    Hi Everyone :smile: I have to create an experiment for my assignment in Physics. I've chosen to do something about Specific Heat Capacity. A boy in my class is also doing SHC so I wanted to make mine a little different from his. I've just recently joined physics (never done it before)...
  23. J

    Latent heat and colligative properties

    I have a couple of questions about this. I know what it is, but need information on specific values. I've been trying to find a table listing as many compounds as possible by their latent heat capacity. I'm also interested in their approximately melting point and would prefer them both in the...
  24. U

    Calculating Energy Requirements for Phase Changes in Water

    Homework Statement how much energy is required to change a 40g ice cube from ice at -10degrees C to steam at 110degrees C. Homework Equations Q=mL Q=mcT The Attempt at a Solution My failed attempt was this, 0.04*120*333000(333000 is the latent fusion heat for water) i don't know...
  25. B

    Thermodynamics question regarding latent heat of fusion of ice.

    Homework Statement (a) An insulated copper container of mass 0.250 kg contains 0.350 kg water. Both the container and the water are initially at 25.0 0C. Then 0.012 kg of ice at 0.0 0C is added to the container. Eventually the container and contents reach thermal equilibrium at 21.7 0C...
  26. P

    Specific latent heat and heat capacity

    Homework Statement 0.1kg of ice was added to a lemonade of mass 330g at an initial temperature of 28 degree celcius and it completely melted. Considering only the lemonade and ice cubes, calculate the final temperature of the lemonade. Given: specific latent heat of fusion of ice= 336000...
  27. S

    Specific heat capacity and latent heat.

    a 210 heater is places in 2 kg of water. What temperature rise is produced if the heater is switched on for 200 seconds? I need your help please.
  28. C

    Calculating Change in Entropy for Water Vaporization at 100oC

    Homework Statement The latent heat of vaporization for water is 540 kcal/kg. By how much does the entropy of 50g of water at 100oC change if the water is very slowly converted into steam at 100oC? Homework Equations The Attempt at a Solution would it be 0 heat change plus the 540...
  29. P

    Latent Heat of Fusion/Vaporization

    Homework Statement Heat is added to a 1.0-kg solid sample of a material at 200 °C. The figure shows the temperature of the material as a function of the heat added. http://edugen.wiley.com/edugen/courses/crs1445/art/qb/qu2/c12/r3-1.jpg What is the latent heat of fusion of this material...
  30. S

    How do I calculate the energy needed to convert ice at -20C to steam at 110C?

    Homework Statement Calculate the energy need to change 9 g of ice at -20 degrees Celsius to steam at 110 degrees Celsius. (C for ice=2.06 J/g, C for water=4.18 J/g, C for steam=2.02 J/g, Hf of ice=334 J/g, Hv of water=2260 J/g) Homework Equations Q=hv / Q=mHf / Q=mc(delta)t The...
  31. C

    What Is the Latent Heat of Ashes?

    I asked my teacher this but he did not know so he asked me to find out. When you set fire to something (for example paper) then when it burns all of the heat is released, is this the reason why ashes become cold so quickly?
  32. V

    Latent heat and binding energy

    Homework Statement Show that the potential height (energy required to separate 2 nitrogen molecules from each other) for N2 is ~ 0.01eV, given that latent heat of evaporation is 210 Jg^-1 and molecular weight is 28 for N2. Homework Equations I'm thinking that this equation might be of...
  33. N

    Melting ice using latent heat and heat of fusion

    Homework Statement What quantity of ice at 2 deg Celsius can be melted by 100 J of heat? Homework Equations q = m c (delta) t (mass x specific heat x change in temp) q = m l (mass x heat of fusion) specific heat of ice = 2.09 j/g-K heat of fusion = 6.01 kJ/mol The Attempt...
  34. S

    Latent Heat - Heat fusion of ice

    The following experiment was performed to determine the latent heat of fusion of ice. A 50.0-g aluminum cup was filled with 100 g of warm water. The temperature of the cup and water stabilized at 35C. A 15-g piece of ice at 0C was placed in the water and quickly melted. The final temperature of...
  35. L

    Need help with latent heat involving ice and steam

    Homework Statement A well-insulated bucket of negligible heat capacity contains 177 g of ice at 0°C. (a) If 20 g of steam at 100°C is injected into the bucket, what is the final equilibrium temperature of the system? I've already solved this part to be 0 degrees Celsius. (b) What...
  36. F

    Calculating Energy Required for Phase Change in an Ice Cube

    Homework Statement How much energy is required to change a 46.0 g ice cube from ice at -10.0°C to steam at 116°C? Homework Equations specific heat c = Q/(m(Tf-Ti)) Q = cm(Tf-Ti) latent heat Q = mL The Attempt at a Solution 2.05*10*46+4.1813*100*46+2.080*16*46 +...
  37. M

    Latent heat of vaporization of H2O ?

    Suppose the latent heat of vaporization of H2O were twice its actual value. (a) Other things being equal, would it take the same time, a shorter time, or a longer time for a pot of water on a stove to boil away? (b) Would the evaporative cooling mechanism of the human body be as...
  38. D

    Solving for Latent Heat of Vaporization: A Student's Journey

    https://www.physicsforums.com/attachment.php?attachmentid=21003&stc=1&d=1255013927 I need help for number 2(b) A student investigates the evaporation of water. He pours 100 cm3 of water into measuring cylinder A and 100 cm3 of water into measuring cylinder B. Measuring cylinder A is kept...
  39. F

    Latent heat of vaporization Water thermodynamic

    Latent heat of vaporization "Water" thermodynamic -first of all I want to know if the "latent heat of vaporiasation " of water is related to the initial pressure of water ? -If LHV of water is variable with the variation of pressure , how can we calculate the heat needed to vaporise a...
  40. J

    Latent heat of fusion for Silver

    [b]1. Calculate the minimum amount of NRG, in joules required to completely melt 130g of silver initially at 15 degrees Celsius. [b]2. ? Q = mC (Tf-Ti) + mHf? saw it online somewhere, not sure what the proper formula for this problem is, and if it is done does everything need to be converted to...
  41. F

    Specific heat capacity, latent heat => ice water steam mixture

    Homework Statement A quantity of 100g of ice at 0°C and 50g steam at 100°C are added to a container that has 150g water at 30°C. What is the final temp of the container? Ignore the container itself in the calc. Homework Equations Q=mc (change in T) Q=mLThe Attempt at a Solution I know how to...
  42. S

    Latent heat effects thermal equilibrium

    Can anyone explain that how the ice's temperature is zero degree and water's temperature is 80 degree are mix and their final temperature is zero degree if the both ice and water has the same mass? Where: mc(delta T) of water = (mc(delta T) + mL ) of ice the result for final...
  43. S

    Latent heat comparing ice to wood

    You bought two kilograms of ice at -10 degrees celcius for your cooler when a friend suggests to instead use two kilograms of wood at -10 degrees celsius. Why should you stick with your ice? Thermal Conductivities Latent Heats Specific Heats Answer with either Good Reason, True but Irrelevant...
  44. C

    What Is the Final Temperature When Ice Melts in Water?

    Homework Statement An insulated cup contains 1kg of water initially at 20 C. 0.50 kg of ice, initially at 0 C is added to the cup of water. The water and ice are allowed to come to thermal equilibrium. The specific heat of ice is 2000 J/kg oC, the specific heat of water 4186 J/kg oC...
  45. S

    How Is the Specific Latent Heat of Fusion for Ice Calculated?

    Homework Statement Determine the specific latent heat of fusion of ice given the amount of time it takes the ice to melt (150 seconds). Energy is supplied to the ice at 530 W. The sample is .25 kg. Homework Equations Q= ml The Attempt at a Solution (Time * 530W) = .25kg * L 150...
  46. F

    How Much Ice Is Needed to Cool Water from 25°C to 10°C?

    Latent heat calculation! Ok... first timer. I am not a science student, done some MBA but wanting some IT course and for entrance exam, I am preparing. I have problem with this one problem. Just provide me a hint. I do calculation part. 'Juice and water is produced from 5.0 liters of water...
  47. V

    Latent Heat Q: How to Lower Temp of 125 g Water to 12°C

    Homework Statement A well insulated cup contains 125 g of water at 23 degrees. How many grams of ice must be added to lower temp to 12? Homework Equations Q = c*m*delta t The Attempt at a Solution energy needed to lower temp: Q = 4190 J / kg * (-11 degrees) * (.125 kg) = -5760 J...
  48. M

    What is the Latent Heat of Fusion and Why Does it Take Heat to Freeze Something?

    I did a lab experiment were we measured the latent heat of fusion of ice but I am not quite sure what that is. I read that latent heat of fusion is the energy(heat) it takes to change liquid to solid. Is that true? Why would it take heat to freeze something?
  49. aussie-girl

    Finding mass of ice in latent heat of fusion problem

    Homework Statement The question is: a 6 pack of cola cans contains m grams of liquid. you want to put ice into a perfectly insulated box to cool it down from Ts to Tf. The ice initially has temp Ti. So (a)how much ice would you need as a minimum. (ignore presence of cans and final state of...
  50. S

    Find the latent heat of fusion of ice

    [b]1. I need to find the latent heat of fusion of ice. The problem scenario is that i have a cup and fill it 1/3 full with water. I then take a cube of ice and put it in the cup. then the cube of ice melts mass of the cup=.24g mass of the cup when filled 1/3 with water=71.16g initial...
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