This chamber is also designed to get you acquainted to the game, and is a simple matter of timing.
As you approach the main area, you will see that there are three sections connected to the main area that have a boundary preventing you from walking directly to them. Fall into the main area, and look through the portal. It will regularly change from the section with a cube in it, to the section with a button, to the section with the exit door. When the section with the cube is visible, go through the portal, pick up the cube, and return to the main area.
You must now wait until the section with the button is visible. When it is, enter it with the cube, place the cube on the button, and return again to the main area.
Finally, you can now wait until the exit door is visible, go through the portal, and exit to the next chamber.
Please move quickly to the chamberlock, as the effects of prolonged exposure to the button are not part of this test.
There's nothing you can do to bypass or finesse anything in this chamber, so just make sure not to waste any time. As you leave the chamberlock and move immediately forward, you will trigger the cycle of orange portal positions. Wait for the one that gives you access to the cube. It isn't hard to get the cube out before the portal switches. Likewise, on the next orange portal put the cube on the button. Go through to the exit as soon as the orange portal changes again, but not beforehand, otherwise you will be stuck in the button side-room for a complete cycle. You should be in the exit chamberlock within 30 seconds from when the entry chamberlock door opens.