Questions about water for Cub Scouts

ScottMP

I am going to speak to my sons Cub Scout troop about plumbing tonight and thanks to Dave Yates I will be doing the old collapsing can full of steam trick.

I remember from my old plumbing class that water expands 11 times its size when heated but it seems to me I was told that water expands 7 times its size when frozen.

When I told this to someone they said " That can't be right, ice cubes don't grow 7 time larger "

Uh ..... am I wrong ? I have an old mind.

I need this for tonight.

Thanks .... I know one of you will have the answer ( Brad ).

Scott

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Brad White

Oh you....

Hi Scott-

It has been a while since I have thought if such things....

As I recall, water expands about 4 percent between 50 degrees F. and 200 degrees F. (Expansion tank rule of thumb.)

Ice expands (due to crystalline structure) by about 12-14 percent depending if fresh or salt water. That old "tip o' the iceberg" thing- the difference in displacement being what is above the surface. 1/7th to 1/8th being the usual ratio IIRC.

You can also stress how important it is that ice does not sink but float when it freezes. Otherwise oceans and lakes would freeze solidly.


Ah, forget all that... these are Cub Scouts! Proud spawn of today's culture!

They will ask, "Mr. Milne!, Mr. Milne! What is the grossest thing you ever pulled out of a toilet???

ScottMP

well there was this one time ....

Actaully the speaker last month was a fisherman and kept pulling out fish they had caught that day. I thought .... hhhmm ... nnnaaaaaa...

Thanks Brad I thought you would have the answer. Should have just e-mailed you

So when water turns to Steam would it be around 11% larger as it expands ??

Scott

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Brad White

Water to Steam

Water expands (or collapses) at about and just under a 1700:1 ratio which is why it makes such a neat vacuum as it condenses.

As an analogy when teaching, I use a "cubic inch of water makes a cubic foot of steam" example. Fairly good visual and close enough (1728:1) for most folks to grasp.

I will have to look up the absolute number but also how that ratio holds across a number of pressures. (If the starting pressures are the same, say atmospheric, does that ratio hold if it is water and steam at say, 100 PSIG...) I doubt it because water is essentially non-compressible as a liquid but steam as a gas is, well, a gas!

Jim Bennett

Can crush

Look at this :

http://www.delta.edu/slime/cancrush.html

Great pic of a tank car destroyed by vacuum.

Unknown

Scott

In regards to the water to ice factor, if the water has no place to expand as it is changing state due to it being in a closed system or condition, the result will be a container that has grown in size or has possibly split open. We see this every winter with the frozen pipes.

I remember getting a small chemistry kit when I was a kid and experimenting a bit with this. I filled test tubes with various liquids such as water, Coke, Downy fabric softener and other things that I don't recall because it was 45 years ago and put rubber plugs in them and left them in the freezer overnight. Needless to say my mother wasn't too happy the next day when she had to clean up all of the broken glass in the freezer! But that's how we all learn! ;>}



Glenn Stanton

Manager of Technical Development

Burnham Hydronics

U.S. Boiler Co., Inc.