For $20\ensuremath{\le}n\ensuremath{\le}45$, two types of quasielastic state-changing-collisional (QESCC) processes, i.e., (i) $l$-changing and (ii) $n$-and $l$-changing processes, have been theoretically investigated based on the free-electron model in which an excited Rydberg electron behaves as if it were "free" and slow with its interaction with a rare-gas atom playing a decisive role. It is shown that a parameter ${u}_{min}[=\frac{\ensuremath{\nu}{\ensuremath{\nu}}^{\ensuremath{'}}\ensuremath{\Delta}E{a}_{0}}{(\ensuremath{\hbar}V)}]$ is quite useful for characterizing both of these QESCC processes in a unified way where $\ensuremath{\nu}(\ensuremath{\simeq}{\ensuremath{\nu}}^{\ensuremath{'}})$ is an effective principal quantum number of the initial (final) state, $\ensuremath{\Delta}E$ is an energy defect, and $V$ is a relative velocity. It is theoretically found that higher-angular-momentum states are dominantly populated in the final channel of these QESCC processes with $1<{u}_{min}\ensuremath{\lesssim}\ensuremath{\nu}$ such as in the $n$- and $l$-changing collision of ${\mathrm{Rb}}^{**}(\mathrm{ns})+\mathrm{He}$. This is in contrast with the uniform distribution over the final angular-momentum states for the usual $l$-changing processes, i.e., ${u}_{min}\ensuremath{\lesssim}1$. The calculated cross sections of these QESCC processes with $1<{u}_{min}\ensuremath{\lesssim}\ensuremath{\nu}$ are found to be in reasonable agreement with experimental findings available at present.