Make sure your fan vents are clean. A little canned air to clean out the dust bunnies as they can get pretty nasty in a short period of time. Also check your fan control settings.
Take off the bottom of the case and use the canned air there also.
Acer's are notorius for running hot and while 80C is not unusual, it's within the limits. Laptops always run warm due to lack of serious ventilation.