Given the task definition and input, reply with output. Given a scientific passage and an answer, generate a question for the given answer.

Passage: Physical and chemical properties of geometric isomers are generally different. While cis -2-butene is a polar molecule, trans -2-butene is nonpolar. Heat or irradiation with light can be used to bring about the conversion of one geometric isomer to another. The input of energy must be large enough to break the pi bond between the two carbon atoms, which is weaker than the sigma bond. At that point, the now single bond is free to rotate and the isomers can interconvert. Answer: different
Physical and chemical properties of geometric isomers are generally what?