Science 5: Osmosis
We're raisin the water content of raisins today with osmosis. Spoiler alert: even through they may look like grapes again, they're still going to taste like raisins. You've been warned.
|Elementary and Middle School||5th Grade|
So the next time you encounter one of these little guys, try this: [Raisin jumping in front of some test tubes]
Put it in a bowl.
Fill the bowl with water.
Watch the raisin balloon up before your eyes. [The raisin swells]
Will it taste like a grape?
This isn't Hogwarts.
C'mon. It's still a raisin.
But it is a pretty neat example of a process called osmosis.
Osmosis is the movement of water from a lower concentration to a higher concentration. [Coop pointing at a blackboard]
So let's go back to our raisin.
Here's the raisin...
…and here's the water.
The water is simply hanging out around the raisin.
What determines if the water will go into the raisin is how much “solute” is present. [Arrows showing the flow of water]
Solute just means any sort of substance dissolved into water. [Dino pointing at a blackboard]
Like when your dad puts a million sugar packets into his morning coffee. [Teaspoon of sugar going into coffee]
That sugar is a solute!
When something is plunged in water, the water molecules pass through cell membranes from
an area of low solute concentration into an area of high solute concentration.
The water moved into the raisin, since it had more solute, and it swells the raisin [Water molecules shown in the raisin]
up, making it bigger.
And guess what?
Osmosis is used by plants all the time.
They use it to take in water for themselves. [Plants next to a stream]
Anyway, if you've ever seen a dehydrated plant before, the stem might look all floppy and weak. [Plant drooping]
Water that plant, however, and osmosis occurs, allowing the water to move into the stem, [Water going into the plant stem]
stiffening it up.
That's osmosis, too.
Animal cells can also use osmosis – but there's a risk involved. [Chickens]
If too much water moves into the cell, that cell can burst, just like a water balloon
you left under the faucet for too long.
In cells, this is called “lysis.” [Water balloon explodes in the sink]
So if you take a cell with some water and solute in it...
…then place it into a hypotonic solution – which just means a solution that has less
solute and more water than that cell –
…then the water will move into the cell, increasing the pressure. [The cell expanding]
However, if you take the same cell and instead put it into a hypertonic solution – which
means a solution with more solute and less water...
Then the water will move out of the cell, leading to shrinking, or plasmolysis. [The cell gets smaller]
Sounds like some sort of alien technology, huh? [People running away from a laser gun]
Plasmolysis powered blaster pistols… [Aliens holding the pistols]
Anyway, you might think this is all a bunch of scientific nonsense with no real world
application, but consider this…
What do people do when they drop their iPhone into the toilet? [Phone falls in and turns off]
Well, after being totally grossed out, they usually fish it out and then place it into
a bag of rice, drawing the water out and saving their phone from imminent death. [Water molecules leaving the phone]
That's right, a cell phone saved, all thanks to Captain Osmosis.
Which even we'll admit is probably not the coolest superhero name in the world. [Guy wearing a mask and a shirt with a big O on it]
At least it's better than Captain Rice Bag… [Guy wearing a shirt with a big R on it]