Water: The Fluid of Life (And Osmosis and Diffusion)

Author: L. A. Briggs // Category: , , , ,

Posted May 3, 2011 at 11:57pm

Water is such an amazing molecule that has many unique features. Without water, life would cease to exist on this planet since life depends on it. Water also has amazing capabilities in the kitchen too. It has great heat transfer properties used when cooking something in boiling water, such as boiling eggs, or when cooling something off with cold water, such as cooling pasta. It is also good for dissolving substances, such as sugar, and for re-hydrating dehydrated foods.

There are two main properties of water that are taken into account in the kitchen: diffusion and osmosis.

Diffusion is the movement of molecules from high areas of concentrations to areas of low concentrations by the random motion of molecules until an equilibrium state has been reached. A good example is the spread of dye within water without being stirred. The random motion of both the water and dye molecules helps the mixture to come to an equilibrium state where the water and the dye are thoroughly mixed.

Osmosis is the diffusive movement of water across a selectively-permeable membrane into a region of higher solute concentration in order to establish an equilibrium of solute to water ratio on both sides of the membrane. A good example is submerging a wilted piece of lettuce in fresh water. The inside of the lettuce leaf has a higher concentration of solute than the water it’s submerged in, so the water diffuses into the leaf in order to equalize the solute concentrations both inside the lettuce leaf and in the water. This essentially causes the wilted piece of lettuce to become rigid again.

The following video is a good example of both diffusion and osmosis. It shows both of the examples that I used above: the diffusion of dye in water, and the osmosis of water into a wilted lettuce leaf.

Recipe of the Day

Spinach and Mushroom Salad

4 slices bacon
2 eggs
2 Tbsp cider vinegar
2 Tbsp water
½ tsp salt
1 lb spinach
¼ lb fresh mushrooms, sliced

Place bacon in a large, deep skillet. Cook over medium high heat until evenly brown. Crumble and set aside. Reserve 2 Tbsp bacon fat. Place eggs in a saucepan and cover completely with cold water. Bring water to a boil. Cover, remove from heat and let eggs stand in hot water for 10 to 12 minutes. Remove from hot water, cool, peel, and cut in wedges. Return 2 Tbsp bacon fat to skillet, stir in sugar, vinegar, water and salt. Keep warm. Wash and remove stems from spinach, dry thoroughly and break into pieces in salad bowl. Pour warm dressing over and toss until coated. Top salad with mushrooms and bacon, garnish with egg.

The original recipe can be found here.

2 Responses to "Water: The Fluid of Life (And Osmosis and Diffusion)"

Jen Says :
5/4/11, 3:14 PM

HOLY cow! That music is so dramatic. It makes osmosis and diffusion seem really, really intense. Like Braveheart does science!

Ckeese Says :
5/4/11, 3:56 PM

I love the lettuce trick! I do it at home all the time! I always forget about my lettuce and celery because I keep it in my drawer at the bottom of the fridge. (oops..) But nothing like soaking it in ice cold water to get some of the crunchiness back :)

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