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OSMOSIS FISH

This is a demo that shows what happens to organisms that live in hypo/hypertonic environments.

Supplies:
2 fish bowls
dialysis tubing
salt
sugar water *
egg white *

* Use leftovers from Egg osmosis activity

PRIOR TO CLASS:
1. Tie end of dialysis bag, fill about half fill with distilled/tap water. Remove air, but leave some room at end of tubing for expansion. Tie end.

2. Repeat and fill bag with sugar water/egg white. * Try to fill the bags with approximately the same size volume.

3. Fill two fish bowls with tap water and label one as FRESH WATER and one as SALT WATER (MARINE)

DEMO:
1. Show students bags and say they will represent "fish" in different environments.
You can even use permanent marker to draw a fish outline on each bag! Have them notice they are the same starting size.

2. Then drop one fish in each bowl. The tube filled with plain water goes in the salt water bowl. The tube with sugar/egg goes in the fresh water bowl.

3. Make a show of adding salt to the salt water bowl. Using a big salt container rather than a shaker is a pretty good visual and the kids will remember which is which.

4. Let them sit over night. The next day check to see "how our fish are doing". The "fish" in salt water will deflate; the "fish" in fresh water will expand.

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