PHYS 1500 Lecture Notes - Lecture 19: Saber Of London, Latent Heat, Qml
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Review: a cup of coffee originally at high temp. Is allowed to exchange thermal energy with environment leading to a total heat exchange of deltaq. From perspective of environment the atmosphere, deltaq is positive. If energy was coffee and atmosphere energy would be neither positive nor negative. Every substance requires a unique amount of energy per unit mass to change the temp. A phase change occurs when the physical characteristics of the substance change from one form to another. Common phase changes: solid to liquid melting, liquid to gas boiling. Phase changes involve a change in the internal energy, but no change in temperature. Then energy q needed to change the phase of given substance is: q=ml. L is called the latent heat of the substance: latent means hidden, l depends on the substance and nature of the phase change.
