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Unit 8: Chemistry Page 23
Have your indicator in a bottle by What’s happening with the
itself. An old soy sauce bottle with indicator? An indicator is a
a built-in regulator that keeps the compound that changes color when
pouring to a drip is perfect. You you dip it in different things, such
can also use a bowl with a bulb as vinegar, alcohol, milk, or baking
syringe, but cross-contamination soda mixed with water. There are
could be a problem. Or it could not several extracts you can use from
be — depending on whether you different substances. You’ll find
want the kids to see the effects of that different indicators are
cross-contamination during their affected differently by acids and
experiments. (The indicator bowl bases. Some change color only
will continually turn different colors with an acid, or only with a base.
throughout the experiment.) Turmeric, for example, is good only
for bases. (You can prepare a
Start mixing it up! When I teach turmeric indicator by mixing 1
this class, I let them have at all the teaspoon turmeric with 1 cup
chemicals at once (even the rubbing alcohol.)
indicator), and of course, this leads
to a chaotic mix of everything. Why does red cabbage work?
When the chaos settles down, and Red cabbage juice has
they start asking good questions, I anthocyanin, which makes it an
reveal a second batch of chemicals excellent indicator for these
they can use. (I have two identical experiments. Anthocyanin is what
sets of chemicals, knowing that the gives leaves, stems, fruits, and
first set will get used up very flowers their colors. (Did you know
quickly.) that certain flowers, such as
hydrangeas, are blue in acidic soil
After the initial burst of but turn pink when transplanted to
enthusiasm, your kids will a basic soil?) You’ll need to get the
instinctively start asking better anthocyanin out of the cabbage
questions. They will want to know and into a more useful form so you
why their green goo is creeping can use it as a liquid indicator.
onto the floor while someone else’s
just bubbled up hot pink, Tip for Testing Chemical
seemingly mixed from the same Reactions: Periodically hold your
stuff. Give them a chance to figure hand under the muffin cups to test
out a more systematic approach, the temperature. If it feels hot, it’s
and ask if they need help before an exothermic reaction (giving off
you jump in to assist. energy in the form of heat, light,
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