Why might a physical change require energy?

1 Answer
anor277
Dec 13, 2017

Well physical changes are largely changes of state....

Explanation:

Well physical changes are largely changes of state...i.e. a phase change, solid to liquid, liquid to gas,,,etc,, and certainly some of these processes involve the INPUT of energy.

Take evaporation...

#"Liquid"+Delta rarr "Vapour"#

....or sublimation...

#"solid"+Delta rarr "Vapour"#

....or even melting...

#"solid"+Delta rarr "liquid"#

These physical processes involve the breaking of bonds in the condensed phase, and thus an energy input is required. What is the energy transfer for the reverse processes, #"condensation"#, #"deposition"#, #"fusion"#?

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