Years ago I was on an archeological dig in Israel. My razor was 120v and
the Israeli voltage is 240v. However, they deliberately were dropping the
voltage to conserve energy so I figured my razor ought to be okay.

It went up in a blue flash and smoked like crazy. I expect your cooktop
will do the same.

I have done exactly the opposite successfully; I had to make room in my
circuit box, so I changed a seldom used 240v heating circuit to 120v. The
heaters don't product much heat, but that just means they run more.