Why would I not see a reaction between aluminum and tin(IV) chloride? I was performing an experiment where I was supposed to construct a modified activity series between certain elements. I decided to use chlorides with the other metals for single replacement reactions so I could compare them all in relation to one another for my modified activity series.

When I placed about one gram of aluminum into about five milliliters of tin(IV) chloride, I was not able to see any reaction taking place. However, aluminum is higher in reactivity on the activity series so I know the aluminum had to react to replace the tin, but why would I not be able to see it?
You need to activate the $\ce{Al}$ to remove the tenacious oxide layer that protects it from reaction. This can be done by a quick wash with dil $\ce{HCl}$, rinse with $\ce{EtOH}$ and finally $\ce{Et2O}$ before adding to the tin chloride.