When my student swipes through a word with his fingers, Chrome opens a new tab and the program disappears. I'm on an Apple Mac.

To fix this issue, we need to disable Swiping between pages' on the Mac because the student is triggering a navigational gesture to move to the next tab. You can disable Chrome's gestures by going to System Preference > Mouse OR Trackpad > More Gestures > and uncheck Swipe between pages, as shown here: