Portal Stories: Mel

Chapter 1:

04:03 - Welcome to Aperture achievement
06:13 - Persistant achievement
10:42 - Testing the Waters achievement

Chapter 2:

0:28 - Long-Term Relaxation achievement
14:17 - Curious achievement
15:54 - You Shouldn't be Here achievement
18:51 - Voices from Above achievement
21:30 - Firefighting 101 achievement

Chapter 3:

02:14 - Beyond your Range of Hearing achievement
02:43 - Electrocution achievement
06:16 - Back on Track achievement
07:16 - Under the Stairs achievement
22:52 - Ignorant achievement
26:34 - Deja-Vu achievement

Chapter 4:

03:00 - Organic Complications achievement
07:47 - Forever Alone achievement
10:59 - Single rainbow achievement
16:47 - Burned in Goo achievement
17:19 - Determined achievement
17:27 - Back off Track achievement
18:08 - Crushed achievement
20:01 - In the vents achievement
21:35 - Into Darkness achievement

Chapter 5:

01:07 - 2056 achievement
08:07 - Shot achievement
10:37 - Welcome to my Domain achievement
14:43 - Story Shutdown achievement

For the last achievement you do not need to restart the entire game, just select Chapter 5 under Advanced Mode on the main menu.
Chapter 5 (Advanced Mode):

12:09 - System Shutdown achievement