internal energy formula

[arielle_cunanan3K]

Is the deltaU=q+w formula only used for gases? since there is a constant V and P for solids and liquids?

[Elena Chan 2L]

I believe you're correct! The internal energy formula, ∆U = q+w, is usually only relevant for work done on or by the system through volume changes or heating that changes volume. Since solids and liquids rarely go through drastic volumetric differences, the difference in ∆U values aren't significant enough to be calculated for. I'm not entirely sure though.

[Jason Ho 2L]

I'm not sure if the rule is strictly ∆U = q +w can only be used for gases. The only thing for solids and liquids is that w would be zero as pressure is constant and the volume doesn't change, so there is no expansion of work.