Overture: Stuck in Chemical Storage

[Frost]

This part pissed me off too because I didn't know what to do for the longest time. I ended up looking up a video on how to get past it, and afterwards I felt incredibly stupid.
You can set a hotkey for the pickaxe by dragging it (in your inventory) to one of the numbers at the top of the screen. It's been a while since I last played, so I don't remember if that's exactly how.

Watch if you want: