Google+ Authentic Parenting: Dances with Lentils

Wednesday, April 30, 2014

Dances with Lentils

Playing with food. My grandmother just punched a hole in her coffin at my mere mention of those 3 words. But we’re going to turn it into a learning experience. See? It all comes good in the end.
Here’s the super quick version. Get some raisins. Get your kids to pour them into a clear glass (the longer the better) of fizzy lemonade, a few at a time. Watch as in a few seconds as they start to bob around (possibly in reggae time) in the glass. Then see if you can get your kids to figure out why that is.


To amp up the fun and learning a little, try these:
  • Try experimenting with other foodstuffs so that they can see what works and what doesn’t. Lentils are great. Some bits of dry pasta work. Put in some boiled pasta (which won’t work) to give them something to think about in terms of why some things work and others don’t.
  • Give them more clues (and increase their deductive reasoning skills) by putting a lot in at once, or putting in new raisins once the old ones have stopped bobbing around. Why do the ones that go in at the end not work as well as the ones at the beginning? Is it something to do with the fizz going? Get them to time how long it takes the first raisins or lentils to start moving, and how long they move for, then repeat it for the last raisins or lentils. Do they see any difference or patterns emerging
  • Make it colourful by adding some food colouring. Does that make a difference to how long or fast the raisins dance?
  • Just for fun, get your kids to choose some music that vaguely is in time to the raisins moving, and video record it for their friends.
Why does it work? The fizz in the lemonade forms pockets or bubbles of air on the edges of the foodstuffs. As they get bigger, or as more form round the edges of the raisin, they lift it up through the lemonade. The less dense the foodstuff, the easier it is for the gas bubbles to lift it, which is why dry pasta works and boiled pasta doesn’t. When it gets to the top of the liquid, some of the bubbles burst, and so the raisin or lentil starts to sink again. Only to repeat the cycle when they’ve sunk a little.
See if your kids observe some of those patterns which will give them a clue as to why it happens. For instance, the denser the item, the further it sinks before rising again. And as the drink gets less fizzy, fewer bubbles form around the foodstuffs, and so they don’t rise up any more. And so on.
P.S. I wouldn’t recommend drinking the lemonade at the end. It’s pretty gross. Don’t ask me how I know…


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