# Science question about weight and volume of water

Discussion in 'Elementary Education' started by shoreline02, Dec 4, 2017.

1. ### shoreline02Cohort

Joined:
Jan 13, 2010
Messages:
632
116

Dec 4, 2017

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

3. ### MrsCMultitudinous

Joined:
Aug 8, 2005
Messages:
14,067
1,884

Dec 4, 2017

What was determined when you taught this concept?

4. ### vickilynMultitudinous

Joined:
Jul 19, 2014
Messages:
12,135
2,958

Dec 4, 2017

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?

Last edited: Dec 4, 2017
5. ### Been ThereHabitué

Joined:
Oct 4, 2017
Messages:
849
518

Dec 4, 2017

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.

Last edited: Dec 4, 2017
6. ### AlwaysAttendFanatic

Joined:
Apr 24, 2012
Messages:
2,855
623

Dec 4, 2017

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?

7. ### rpanCohort

Joined:
Mar 19, 2017
Messages:
703
540

Dec 4, 2017

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

vickilyn likes this.

Joined:
Jul 28, 2017
Messages:
1,484
1,025

Dec 4, 2017

I agree with this.

https://inquiryproject.terc.edu/curriculum/curriculum5/3_ice/inv_11/index.html

Peregrin5 likes this.

Joined:
Aug 8, 2005
Messages:
14,067