Friday Sprog Blogging: experiments currently underway.

Oct 30 2009 Published by under Chemistry, Kids and science

The Free-Ride offspring have been rather busy recently, what with the approach of Hallowe'en and the rapidly approaching end of their regular soccer season. (The post-season, of course, falls after this weekend's time change, which means practices will either be earlier or darker.) Still, each of them has found time for an experiment they'd like to share.
From the elder Free-Ride offspring, a model of the water cycle:

WaterCycle.jpg

What's pictured here is a sketch; the actual set-up is at school.
The elder Free-Ride offspring carefully added soil to an empty 2 liter bottle, followed by a sprinkling of grass seeds, followed by a bunch of tap water. The bottle was then capped and placed on a counter that gets some sun.
After some time in the sun, the interior of the bottle got foggy. ("Evaporation!") When it cooled down, the fog was replaced by droplets on the walls of the bottle. ("Condensation!")
The grass seeds have not sprouted yet. When they do, we'll report back on how (if at all) living plants in the system seem to affect the patterns of evaporation and condensation in the bottle.
From the younger Free-Ride offspring, an experiment with eggs and vinegar:

EggsVinegar.jpg

This is actually an experiment idea that the younger Free-Ride offspring brought home from the after school program. We haven't done this experiment before, and we're not sure how it will turn out, although we've been assured that the results will be ... interesting.

EggCups.jpg

The set up is really simple: put an egg in a cup, pour in white vinegar to cover, and let it sit there for 24 hours. Of course, I figured while we were at it, we should try it not just with a raw egg (in the blue cup) but also with a hard boiled egg (in the yellow cup).

EggsFizz.jpg

When the vinegar was added, visible bubbles formed around each of the eggs. The bubbles seemed to form more rapidly around the hard boiled egg, possibly because it was still warm from being boiled. (Some chemical reactions go faster at higher temperatures.)

Eggshells.jpg

Because we wanted to check our guess that the bubbles had something to do with a reaction between the vinegar and the eggshells rather than the eggshell contents, we dipped into the canister of eggshell bits we keep on hand (to spread in the garden around tender plants to discourage marauding gastropods). We put some eggshells in a cup and poured on some vinegar.

ShellFizz.jpg

The eggshells in vinegar generated lots of bubbles and even some audible fizzing. The acid in the vinegar must be reacting with the calcium carbonate (the substance that makes up eggshells). That means the bubbles are probably carbon dioxide.
And what's left when the vinegar and the calcium carbonate have produced those carbon dioxide bubbles? What will become of the shells on the raw and hard boiled eggs after a 24 hour soak in the vinegar?
We'll check in tomorrow after we've found out!

6 responses so far

  • anon says:

    isn't it all chemical reactions that go faster at higher temperatures? The reactions also work well with citric acid - when life gives you lemons, it's time for science.

  • Rick Pikul says:

    There are some that slow down, (such as many enzyme catalysed reactions), also it is possible to be under conditions where an equilibrium shift will occur.
    As for the faster reaction with the hard boiled egg: I have an idea what's happening, and it should still happen even if the eggs are at the same temperature. The calcium carbonate is not the outermost layer of an egg, boiling likely resulted in the protein layer being at least partially removed.

  • Eric M says:

    This was one of my favorites, back in the day. If you haven't yet, put a fresh egg under enough vinegar to remove all of the shell. The inner shell membrane should be intact, showing all the internal layers. Very neat for a ~12 year old protogeek. Demineralizing bone is quite slow in vinegar, but the emergence of the collagen is neat, when compared to a control bone.

  • Leah says:

    I don't know what the younger sprog's class is planning to do with the eggs post-experiment . . . but I suggest you do this with another egg or two and then work on an experiment to understand osmosis. Put an egg in pure water, an egg in really salty/sugary water, and an egg in moderately salty/sugary water (or try multiple permutations of all those). I did this long ago, so I don't remember if salt water or sugar water was the key. But rest assured that you may see some interesting results that help the sprogs understand solute/water movement.

  • kashay says:

    this is the coolest thing i have EVER SAW IN MY LIFE AWWWWWWWWWWWWWWWWWWWWWWWWWWWWSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSOOOOOOOOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMMMMMMMMMMMMMMMMEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE

  • carla says:

    i liked it