They sound the same, but a space makes all the difference. Into and in to have different uses. Here are some examples.
Motion or Direction
He walked into the room.
(Which direction was he going? Into the room. In the above sentence into is a preposition.)
Squiggly walked into the lamppost by accident.
(Into is a preposition showing motion and direction.)
“Step into the shower.”
(Into indicates movement and it is a preposition.)
In or To Are Part of the Verb
We broke in to the room.
(Broke in is a phrasal verb. The word in belongs with broke. The word to is a preposition to tell the reader where the action of the verb happened. Where did you break in to? The room.)
Squiggly walked in to hear Aardvark talking about the surprise party.
(Because to is part of the verb hear [to hear, an infinitive], keep it separate from in.)
Infographic images courtesy of Shutterstock.