# 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. ### Problem about a block of ice melting (specific latent heat)

Energy lost by water = Energy gained by ice Energy lost by water = 0.16 x 4200 x (100-t) Energy gained by ice = 0.205 x L + 0.205 x (t) (where t is the temperature at thermal equilibrium). However, there does not appear to be enough info to continue. The solution, however, considered t to be...
2. ### Thermodynamics - Latent Heat Problem (finding mass)

Can someone walk me through this? Our teacher didn't bother to meet us synchronously ever since and I'm kinda stumped on solving this. The equation I used for this problem is: mi = [mw(cw)(ti-tf)]/[Lfi + (Tf - Ti)] mi = [190(1)(23-3)]/[79.6+(3+20)] = 37.04g mi = mass of ice mw = mass of...
3. ### Vaporization latent heat vs boiling point

answer is 78oCdelta G = delta H - T delta S -235,310- (-277,690) = -38.56e3- T (282.59-160.70) T = -664K I am not sure if my concept is correct. May anyone help a little bit on that please? thank you
4. ### Specific latent heat of fusion of ice question

a) Ew = EL + Ei mwc(T2-T1) = miL + mic(T2-0) 160 x 4.2 x (30 - 20) = 20L + (20 x 4.2 x 20) L = (6720 - 1680)/20 = 252 J/g b) accounting for 3 gram of melted ice 160 x 4.2 x (30 - 20) = (20 - 3) + (20 x 4.2 x 20)...

6. ### 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...
7. ### Is latent heat only released and absorbed as radiation?

Can water simply absord the kinetic energy from colliding air molucules to change its phase? And can water transformed into ice simply have the kinetic energy of its molecules increased to balance out the lost latent heat? Would not this again change ice into water?
8. ### Question about thermal physics -- Ice cubes melting in water

First, I calculated the heat required for the ice to melt: Q=mLf Q=0.150×330 Q=49.5 J Then, I calculated the final temperature of the water by forming the following equation: Q=mcΔT −49.5=(0.15+0.35)×4200×(Tf −80) Tf=80.0 degrees Celcius But the answer says 32 degrees Celsius.
9. ### Finding latent heat of vaporisation

Can anyone please help me on how to tackle this question? I really do not have any clue to make a start on it? Thanks for any help!
10. ### Phase transition between two phases with different Cv

I actually can't figure out what kind of phase transition it is and how to proceed through..!
11. ### 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...
12. ### Higher and Lower heat value of combustion of Coal?

hello my friends , i have two question about calorific value of coal why Lower heating value decrease with increase oxygen content but increase with increasing hydrogen , sulfur and carbon content ? Do this elements influence the higher heating value or not ?
13. ### Latent Heat: An Alternative Explanation

1. In studies of the heat budget of the global free atmosphere, the concept of “latent heat” (now known as “enthalpy of condensation”) plays an important role[1]. 2. Both observation and experiment confirm that when humid air condenses the temperature of the remaining air increases[2]. 3. This...
14. ### Understanding the Derivation of the Latent Heat and Entropy Equation

Homework Statement I came across this equation ##L / T = \Delta S## and am not too sure about its derivation. From what I know, ##L = Q/m## and ##Q = TdS ##. Substitution gives me ##\Delta S = mL / T## which isn't correct. Could someone assist me in understanding the derivation? Thanks...
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### Thermal physics -- Latent heat melting ice

Homework Statement Question (b) (iii) Homework EquationsThe Attempt at a Solution The energy required to melt the ice is Q1=mL=3*0.025*3.3*10^5=24750J The energy released by water is Q2=mcT=0.33*4200*(22-T) Shall I calculate the energy that the ice needs after it melts into water? i.e...
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46. ### What is the latent heat of the water evaoparation

since water can turn into steam at any temperature, what is the latent heat of water evaporation. I know the late heat value at the boiling point. but what is the latent heat at 20 Celsius
47. ### Latent heat of fusion for water question

Hello, I am doing some research involving supercooled water flash freezing into ice. I am doing some calculations and I think that I must be wrong judging by my result. Using the latent heat of fusion of water, and the specific heat of water, I can calculate a temperature value which should...
48. ### Latent Heat in Solid-->Liquid transitions (phase change)

Homework Statement Show that in Solid to Liquid transitions at T \ll {T}_{c} , L\simeq constant where {T}_{c}, L are the critic temperature and latent heat respectively. Homework Equations \left( \frac{d ( \frac {L} {T})} {dT} \right) = \frac {{c}_{p2}-{c}_{p1}} {T}+ \frac...
49. ### Modeling of moist-adiabatic temperature?

Hi, I need to find some good article or book related to the modeling of this process: the parcel of air goes up from the surface to the top of troposphere ( to 12000 m ), we know the conditions at the bottom such as temperature, pressure and humidity, we assume that the parcel is isolated...
50. ### Latent Heat Solid->gas Liquid->gas transitions

Homework Statement Show that in Solid to gas and Liquid to gas transitions at T \ll {T}_{c} , L\simeq a+bT where {T}_{c}, L are the critic temperature and latent heat respectively and a,b constants.Homework Equations \left( \frac{d ( \frac {L} {T})} {dT} \right) = \frac...