Hello! I am shuffling through old curriculum to formulate a new test and am not sure about this test question... "How does water change as it evaporates?" I'm thinking the answer is B? A. weight and volume increase B. weight and volume decrease C. weight increases, volume is unchanged D. weight remains unchanged, volume increases Thanks for your help!
I answered B because I can't imagine a completely closed system in most high schools or younger, that would allow you to weigh the water vapor, but I can understand where Been There is coming from. If you were to change the question into water change as it freezes, air is trapped in the formation, which makes ice float. Is this particular question correlated to something you have taught or studied specifically?
I believe the correct answer is D. The number of molecules remains the same whether they are in liquid form or have evaporated and therefore retain the same weight. After the water has evaporated, the molecules no longer restricted to a fixed volume and the space between the molecules increases significantly (unlimited in the air), so its volume actually increases.
Personally I would dump this question unless it is alligned with a NGSS DCI. If it is, the answer should be there. If not, why are you assessing it?
perhaps change the question to an open ended question rather than multiple choice so students can answer as they see fit and justify their answers accordingly
I always tell my students that my purpose, when testing them, is never to try to trick them. I only assess what I have taught and what they have had an opportunity to practice in class. I will, within my assessment, provide opportunity for extension for those who welcome the extra challenge, but if I'm not sure I taught a concept, it won't be tested.
