Well, if you can pull it off, a 4.0 GPA will get people interested. However, the fact that you did nothing ELSE is going to raise HUGE flags for any admission committee. Someone who's only taking nine hours at a time I'd expect to see at least two of the following (and maybe more): work experience, big research experience, lots of clinical exposure, other volunteer/service EC's.
Also, expect to be grilled how you'll handle med school (Often described as being "Like drinking from a firehose") when you've never taken a full class load.