The scale reading does not change, in either case.
Work Step by Step
Consider the system consisting of the objects on the scale. The system, which is placed on the scale, does not change, before and after the block is placed into the liquid. The scale reads the weight of the system. Another way to answer this question is to remember that forces between the block and the water are internal to the system. Gravity and the support force from the scale pan are external to the system, and are unaffected by the internal forces. So the scale reading is unaffected. This is discussed on page 254.