Rising Raisins and Pop Bottle Fountains - A Science
Inquiry Experience - Part 1
By Thomas Smith
Sometimes the classic science experiments / demonstrations are classic
for a reason. They're just wonderful at grabbing the attention of
students and getting them to think about their world. Such is the case
with the delightful "Rising Raisins" and the awesome "Soda Pop Bottle
Fountain". By combining the two, the kids will be begging for more.
First, the "Rising Raisins" have been in print forever, usually just as
a diversion or bed time sleep inducement. For this activity it will be
used to enhance observation skills as well as a spring board for a
discussion of density. Feel free to adapt the activity and questions to
suit the age of your students.
Though soda will work for this activity, I always use seltzer water.
Soda has a tendency to get sticky upon drying while seltzer water will
just evaporate with no mess. No mess, that's for me.
You will need a sealed two litre bottle of seltzer, a tall clear
container, raisins, other testable items.
Ask the student to inspect the sealed bottle. What is seen? (Clear
liquid) Are there any bubbles? (No) Now, open the bottle and ask what is
seen and possible reasons for the occurrence. (Lots of bubbling, foaming
over. Also, sound is heard. This could be caused by a reduction in
pressure once the bottle is opened.) Where did the bubbles usually form?
(On the bottle's walls) I wonder if bubbles need something on which to
form?
Now, pour the seltzer water into the tall clear container. No doubt,
more bubbles will form on the container's wall. Show a raisin and have
the student predict what will happen when it is placed in the container.
When added, the raisin will sink to the bottom. There, bubbles will form
in its nooks and crannies. This will cause the raisin to float to the
surface where the bubbles will pop. The raisin will sink again and the
process will continue until little gas is left in the seltzer water.
At this point, the experiment can go in two ways. One is for the student
to suggest other items that might sink and float like raisins. What are
the characteristics of these items that allow the activity?
(Lightweight, not really smooth, etc.) Objects may include pieces of
broken spaghetti, macaroni, straws, penny, marble, etc. Students can
categorize objects that move and those that don't, then create possible
reasons for their activity or inactivity.
Older students may be engaged with a discussion of density once they
understand it fundamentally. Why did the raisin float? (It had bubbles
around it.) Why didn't the bubble surrounded penny float? (Too heavy) Is
the raisin's mass more or less at the top? (Same - the mass of the
raisin itself remains the same just as your mass remains the same if you
are on the ground or jumping into the air.) Continue questioning and
move to questions about density. If we were to find the mass of the
raisin and the mass of the same volume of water, which would have more
mass? (Raisin - it sinks in water). If we were to find the mass of the
raisin and its bubbles and the same volume of water as the raisin and
bubbles which would be greater? (Water - the raisin/bubbles float
because they have less mass combined as the same volume of water). And
so goes it... As an inquiry questioning device to check understanding of
density, the "Rising Raisin" is a winner.
Next time, we'll take the bubble formation ideas and use them in
creating the "Awesome Pop Bottle Fountain." Have fun!
Tom Smith, an elementary science teacher, owns and operates Wonder
Workshops, an online Mecca of hard to find retro toys, puzzles, magic
tricks, puppets, books, and DVDs all based in science, math, and problem
solving. He also presents hands-on science workshops around the country
for teachers and parents. Be sure to visit the store and workshop site
at
http://www.wonderworkshops.com. You'll be glad you did.
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