Mass and Volume of Water

 We started our study of water by talking how much of the earth is covered by water (70%) and then of that water, how much is salt water (97%), frozen water (2%), and fresh water (1%).  

This really surprised all of Room 5!

 From that, Room 5 brainstormed the properties of water. 

 Each table group was given 2 cups and 2 graduated strips.  Their job was to tape the graduated strips to the sides so the water could be measured.

 Next, each cup was to be filled with 100mL of water.  Cup A was weighed...using grams.

 Once Cup A was weighed, Cup B SHOULD have weighed the same since they were both 100mL.

 Wrong!  Not a single groups cups balanced each other.  Why?  Jaya came up with the idea (correctly) that the graduated strips had not been placed exactly in the same positions.  We then worked to get the cups equal. 

When the mass was equal (mass is weight), one cup was covered in plastic (from each group) and placed in the freezer.  The other cup was also covered in plastic, but left at room temperature.

 Room 5 predicted what would be the difference in mass and volume after the water was frozen...would it stay the same, would it be less, would it be more? 

 Surveying the class, most of Room 5 agreed that the cups with frozen water would weigh more than it had as a liquid.  They also felt the volume would decrease...or stay the same.

 Oops!  This was when Group 2 discovered their 2 cups, each with 100mL (supposedly) didn't have the same mass.  (weight)

 Oops!  These weren't equal...

 neither were these...

 or these...

 

We put the jars to freeze in the freezer in the nursing office...

and now we had to wait...till Monday!

I didn't take pictures when we continued our experiment on Monday.  But some of facts we learned:
The mass of water does NOT change when water is frozen...but the volume DOES!  In every group, the volume increased at last 10mL!  Most were shocked at these results.  Our discussion then centered around times Room 5ers have put a soda in the freezer...only to have it burst.  I told them about a jar of soup I had frozen...and I had filled the jar too full.  What did it do?  Cracked/broke the glass.  Why?  Because the liquid expanded and there was no where for it to go. 

From that discussion, the question was posed...if there was 100mL of liquid water, and 100mL of frozen water, how would the frozen water compare in its mass?  After discussions in their table groups, most concluded that the frozen water would weigh less.  Kate talked about how icebergs float...Kathryn referred to the fact that our 100mL of liquid water expanded when it froze, even though it still had the same mass.  So, she concluded, if you took some of that ice out so it was only 100mL, it would weigh less.

There was some great thinking going on in Room 5!