Find $ΔU$ for the combustion of methane in a sealed rigid adiabatic container.
Solution says since $q = 0$ and $w = 0,$ so $ΔU = 0$ by the first law of thermodynamics.
Why isn't the heat released during combustion considered?
Does the temperature of the system changes during the process? I know that
$$ΔU = nC_VΔT$$
is not valid directly as the amount of substance is changing, and so do the degrees of freedom.