You cannot get speakers to work by plugging them into your line in jack, no.
A headphones/speakers jack, or a line out jack, will work. Like a microphone jack, a line in jack is for capturing audio--you would plug a device in that sends a sound signal to your computer, not the other way around.
If you've done something like this with your computer before (in Windows, you said), then either:
- It's not really your line in jack, or
- your line in jack doubles as an output jack for some of the speakers in your surround sound system. (Then it still cannot send output to speakers when used as a line in, but it has other uses also.)
If it worked in Windows, it should work in Ubuntu, but you would have to provide much more information about your computer for us to know. In particular, we'd need to know exactly what motherboard you have and what sound chipset it uses. A detailed description of all the audio jacks (including their colors and and symbols) would be especially helpful, and a picture might be a good idea.