Tuesday, November 3, 2009

Experiment 2. An acid plus a base

Science for preschoolers and small children, (cont). Here's an easy one that you can do in 3 min. Baking soda plus vinegar gives loads and loads of fizzy bubbles.

This "science trick" loosely demonstrates that sometimes, mixing two substances together gives a reaction. If you like, you can start off with some other mixtures that don't give a reaction, just to hammer the point.
For example:
If you mix sand and water nothing happens.
If you mix water and sugar the sugar dissolves, but that's all.
If you mix baking soda and vinegar, you get loads of fizzy bubbles, wow!
We played around with this for about 20 minutes, working out how much we baking soda we could put in the glass without the bubbles fizzing over. In the end we came up with 1 t baking soda and 1/4 c white vinegar.
The chemical reaction here, in case you're interested, is that mixing an acid with a base gives a salt plus water. A byproduct of this reaction is the production of carbon dioxide, which is given off by the baking soda as the acids rip off their hydroxyl group. My kids don't care about that part, and it would kill the fun if I started going on about that anyway. This science trick is all about noticing a reaction occurring.
Okay, that was fun. But do you want to see it in slow motion? Lets use vinegar to react with a different base: an egg shell. The egg shell is made of an alkaline calcium compound. If we drop an egg into some vinegar and leave it a while, the vinegar will dissolve that shell clean off, leaving a funny wobbly shell-less egg.
Here goes: Get a load of this! As soon as you cover the egg in vinegar there are zillions of little bubbles forming. That's the carbon dioxide again, being produced as the acid reacts with the base. All those bubbles make the egg float. It's like watching a lava lamp as it bobs to the top of the jar. The shell starts to dissolve off in layers, see?
After a day, we washed off the last bits of the shell under the tap. It was soft and chalky and washed off with no problem at all. We all held the wobbly shell-less egg.
If you think the kids look a little underwhelmed it's because they are. "That's kind of disgusting Mum", said Harry.
Well, yes it is I guess. Perhaps this is also a lesson in how we do not like it when people use chemicals to mess with our food.
Me: "Yes it's funny to see an egg without a shell. But isn't it cool that the vinegar dissolved the shell off?
Harry: "Um...well I just don't know."
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14 comments:

  1. I...I think I'm speechless. Its like your science self, craft self and mother self have all come together for this one moment of creativity. What's that called? Something...there's a word for that, when things come together like that. What is it? Well, I need to work on my vocab. I love your kids faces in the photo. And they are beauties!

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  2. cool experiments, just perfect for young, inquiring minds... our kids were introduced to the joys of cleaning with white vinegar + baking sode + a little elbow grease = great cleaning product! great post!!!!!!

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  3. Hee hee the honesty of underwhelmed children!

    But can I ask for a little more technical detail? Through the eggshell-dissolving process, how does the eggwhite become solid?

    These posts are fabulous. When Flynn has an attention span lasting a little longer than the current three seconds, I will be referring back to these, for sure.

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  4. Hi Nic, the egg white doesn't become solid at all, no sir. The egg you see above is a plain old raw egg, still liquid inside, but surrounded only by the membrane that lies just inside the shell.

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  5. Miss Smith that eggshell trick is fantastic, it really rips my hydroxyl group! I always suspected you knew magic. Thanks for an enlightening Tuesday. Lindy x

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  6. Love the eggshell one...will have to try it :-) We're big fans of good old "stinky cabbage water" as they call it at Playcentre. Have you done that one? It stinks to high heaven but is very groovy for its acid/base indicator properties ;-)

    J

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  7. Hi Jen,

    Am tempted to try those experiments just to amuse myself - although I fear if I attempted it while Louis was around, he would try and eat the egg..

    The older I get, the more I think science is a great pursuit and career option - wish I had taken more interest at school. If Louis has any science homework questions, we'll get him to ring Auntie Jen.

    Love Mary

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  8. LOVE their underwhelmed and skeptical expressions! I also adore your fingers holding that squishy egg with no shell.

    As an aside, do you know that when hens are learning to lay eggs, sometimes it's a little (as you might say in NZ) wonky and they come out teeny (like a thimble) or enormous (like two yolks!) or shell-less?

    XO
    Iris

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  9. Hey Jen, it's great the way you've put those photos together. Bubbles are so much fun whichever way you make them and this is the perfect time of year to be reminded of that. Just read the blog out to the big boys who are studying for science. Who knows? It may come in handy.Louis did a double take on the comments. 'What the ...hey, is that me?' No its Llouis (little louis)

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  10. Oh that's cool, thanks for explaining. I'm going to try it, whether or not Flynn is into it. Currently his main "experiment" is tattooing his forearms with felts, today he looks like he's just come out of prison.

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  11. Hi Jen - do you mind if I print off the last 2 posts and put in a folder in the staff room for teachers to try. I could get feedback from them if they find the experiments useful and your explanations etc? THought I'd check first so as not breach your intellectual property rights. Cheers Marg

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  12. Sure thing, Marg and others. Please feel free to print and use any of these posts and let me know how you get on.

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  13. Oh my goodness! I am thinking shell-less eggs are the most super cool extra special eggs on the planet!

    We are so doing this next weekend!

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  14. Love Harry's response to "Isn't that cool?" with "Um well I just don't know". I felt the same way in inorganic lab in college sometimes!!!

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