An oil spill covers 4 square kilometers in 1/4 of an hour. At this rate, how many square kilometers will it cover in 2 hours?
In 1 hour, the oil spill will cover 4 square kilometers x 4 = <<4*4=16>>16 square kilometers.
Therefore, in 2 hours, the oil spill will cover 16 square kilometers x 2 = <<16*2=32>>32 square kilometers. Answer: \boxed{32}.