Students often mix up “so” and “so that” in their essays. Here’s what you should know.
“So” is used to indicate an effect or consequence of something. Like:
I studied hard, so I got a high score.
The effect of studying hard is that I got a high score.
There was a drought, so the people moved west.
The effect of the drought was that people moved west.
I’m tired, so I’m going to bed.
The effect of being tired is that I’m going to bed.
“So that” is used to indicate the purpose or reason for doing something. Like:
I turned up the heat so that we will feel more comfortable.
My reason for turning up the heat was to make us feel more comfortable.
People moved west so that they could grow crops.
The reason people moved west was to grow crops.
I should go to bed early so that I have plenty of energy tomorrow.
My reason for going to bed early is that I want to have more energy tomorrow.
Some old-fashioned writing uses “in order that” in a similar way. I don’t recommend using that form in contemporary academic writing.