If the polarity of the solvent increases, will the Rf value increase or decrease? True or False: A sample of aspirin has an $R_f$ value of 0.20 when measured on a silica gel TLC plate with a certain solvent mixture. If the polarity of the solvent is increased, the $R_f$ value of the aspirin will become larger. 


Would this be false? Because aspirin is polar (I believe would be considered polar because it dissolves in water despite some other sources saying that it is actually non-polar) and the silica in the TLC plates are also polar, aspirin would not be able to travel very far because it would interact with the silica. Thus, shorter distance over longer distance = lower $R_f$ value, with $R_f$ = distance spot moves/ distance solvent moves.
I wish we would stop teaching chromatography in terms of "polar" and "nonpolar." 

The aspirin will interact fairly strongly with the silica due to hydrogen bonding/electrostatic interactions of the carboxylic acid and the ester with the silica. If you increased the "polar" component of the mobile phase, it would travel further due to the mobile phase competing more for binding spots of the silica gel.

So increasing the polarity of the mobile phase does raise $\mathrm{R_f}$ of aspirin (or anything) on regular silica gel.