But...she was wrong. If the teacher corrected her in front of the class, it had to mean that your daughter gave misinformation in front of the class. As opposed to giving your daughter a sugar coated "Almost!" and letting the other children think that if the information that your daughter gave wasn't right, it must be awfully darn close, she nipped it in the bud.
At six, no one expects her to know all of the answers. It's cool that she's wrong, because she's at school to be taught and corrected.
In your situation I'd probably go over the book once more with her and tell her that it looks like we made a mistake. Then let it go.
Eepster- Gen ed 2nd grade teachers still have to take chemistry and first year physics. Even if they graduated last year. Even if they chose not to do another semester of science after that. But a lot do anyway, and they're in the same frosh science as everyone else. No one is setting out to make second grade teachers look stupid.
Furthermore, what's wrong with second grade science being taught to second graders? A theoretical physicist with a "deeper understanding" won't have much in common with a second grader. S/he'll confuse her.
You seem to be contradicting yourself all over in this post. 2nd grade teachers should know science, but shouldn't have to explain why and answer is wrong? It's not "sugar-coating" to explain why an answer is wrong (in this case for instance "energy can become matter and matter can become energy, but they aren't actually the same thing") it's teaching. I bet if another child had answered "dirt!" the teacher would've said "good that's a type of matter, anyone else?" even though matter isn't dirt. Because you know what? It's second grade!