Scenes are one unit of action, eg a fight.

Chapter: a group of various scenes

Cut the previous chapter at the closest a natural cliffhanger*, then start your new chapter. Group together scenes to fit your theme or pace. The grouped scenes should display a three act structure for a certain development.

Rough aim for a 100k word novel: 20 chapters of about 5k words each.

*Do not end every chapter with a danger cliffhanger.

Each chapter in your book tells a mini-story that forwards your overall plot. Logically, you don’t need for chapters at all. You, the writer, could start the book on page one and keep going right to the end. However, chapters create a more user-friendly book by giving the reader “resting” places. They give readers a sense of accomplishment.  The chapter title hints at something to come, something worth waiting for.

There is no industry standard, only an average and that’s about 8-10 pages per chapter. Extremely short chapters (1-2 pages) are used for dramatic effect, enforcing the importance of a single event. Long chapter create a sense of real time.