The impact of a change can affect:
-Just the direct activity itself
-All downstream activities, and
-The project's fixed cost, or project overhead, based on an increase/decrease in overall project duration
Remember that depending on what the change is, you may have to go through all, or a large portion of the planning processes all over again, including, but not limited to:
Scope
Risk
Schedule
Cost
Find a project online (make sure to cite the source) and evaluate the impact of the change in regards to the criteria above (at a minimum). Discuss how some of the afore-mentioned elements affected the project, and what steps were taken in change control to mitigate them.