I’ve spent many years asking for a side of fries with my meal.  Unfortunately, I’ve reached an age where (perhaps) that is not the best idea all of the time.  Don’t get me wrong!  I love the salty crunch of a deep-fried potato.

However, the more I look at my eating habits over the past few  years, the more I realize how often I turn to our green friends for dinner.

And so, this week, I want to pay homage to…

The Salad!

There is a lot of science going on inside a fresh salad – fruits, stems, roots, leaves…

I COULD GO ON ABOUT THIS ALL DAY LONG!

But I believe we will focus on one little trick that has been known for centuries about salads; namely, how to keep lettuce fresh and crisp.  To do this, we need to review the four main concepts about science in the kitchen:

I’m willing to guess that most of you have seen what happens to the lettuce or any of the vegetables in a salad when it has “gone bad.”  The lettuce wilts as it loses its crispy texture and turns into a gooey mess.

I don’t know about you, but I like the crispy feeling of lettuce when I take a bite.

So how do you keep lettuce crispy?  Easy!  Just put the lettuce in some water and wait for it to firm up again!  How does that happen?

BRING ON THE ATOMS…

The “crispy” feeling of fresh lettuce is really a high DENSITY of water molecules inside the plant cells.  Remember, a molecule of water is a group of three ATOMS (two hydrogen atoms and one oxygen atom).

When these cells have a high DENSITY of water, they are very full of water molecules which make the lettuce feel crispy when you break it apart.

However, large amounts of molecules (like water) tend to move to areas where there are fewer molecules.  This DIFFUSION of water molecules takes place as your salad sits in the bowl for a few hours.  The water moves out of the plant cells and causes the entire lettuce leaf to become limp and soggy.

If you place your wilted lettuce leaf into a glass of water, you will notice after awhile that it will start to get firm again.  But how does the water get back into the lettuce?

DIFFUSION TO THE RESCUE

Since there are more molecules of water in the glass than in the cells of the plant, the water DIFFUSES back into the plant cells.

EUREKA!  YOU HAVE BROUGHT LETTUCE BACK FROM THE DEAD!

Of course, you cannot do this trick too many times OR with lettuce that is too wilty.  Just be certain to keep the lettuce nice and cold while you keep in under water.   Heat tends to do bad things to plant cells (and everything else for that matter.)

A SIMPLE LAW FOR YOUR SALAD

What does heat have to do with your wilted salad?  Well, the ATOMS within your lettuce are moving around a lot more as they heat up in that bowl of salad.  They are not being destroyed though.  This is because the LAW OF CONSERVATION states that atoms cannot be created or destroyed, only moved around.  And if you remember, it is the DIFFUSION of water molecules out of the cells that started this whole problem to begin with!

BESIDES THIS TRICK, WHAT IS THE BEST WAY TO KEEP YOUR SALADS CRISPY?

Eat all your vegetables as soon as you can! (You’re welcome Mom!)

Check out the Classic Science:  Physical Science and Chemistry curriculum to learn more about ATOMS, DENSITY, DIFFUSION, and the LAW OF CONSERVATION!

Also be certain to subscribe to Mr.Q’s blog every Thursday to learn more about how to teach science with cheap, everyday items!

Tags: atoms, Classic Science, cooking, density, diffusion, food, law of conservation, science