Today, I did a science experiment all about salt and lettuce!  What a strange combination!

I began by putting some water into two bowls and adding quite a bit of salt to one of them -

As you can see, the Olympic Games was on TV in the background, but it didn't distract me at all!

I then took some lettuce and put one leaf into each bowl -

This is the lettuce in the bowl of salty water, and this is the lettuce in plain water -

We then left the lettuce in the water for 30 minutes (during which time we actually did watch the Olympics more carefully!).

After the 30 minutes was up, I lifted each lettuce leaf out of its bowl to see if they had changed at all.  The lettuce leaf that had been in the salty water had wilted (become limp).

Whereas, the lettuce leaf that had been soaking in the clear water had not changed - it was still as crisp as it was when it went into the bowl.

Why was this?  Lettuce is crisp because of water in its cells.  Cells in lettuce (like the cells in our bodies) are surrounded by a selectively permeable membrane - a barrier that lets some, but not all, materials to pass through.  Water moves through this barrier in the direction of lower water concentration.  When I added salt to the water, the water concentration went down and water from inside the lettuce cells moved out of the cells through the membranes into the salty water.  This is what made the lettuce wilt!