Got Shells?
Updated 4/2008
Theme/Message
A more acidic ocean is bad news for shell-building animals.
Audience
General visitors: Families, children, adults, etc. Can be walk up activity table or classroom
program
Materials
Baking soda and small carton for display (sodium bicarbonate)
Vinegar and small bottle for display (acetic acid dissolved in water)
Lemon-Lime soda and can for display (carbonated water, high fructose corn syrup, etc.)
Lemon juice and small bottle for display (citric acid)
Water and bottle of water for display
Activity Cards (More acidic, less acidic)
Pipettes, 4 per tray
Test tubes and holders, 4 tubes and 1 holder per tray
Safety glasses, 1 pair per tray
Trays, 4-8 (plastic salad plate can also be used)
Diapers/paper towels
Brock Microscope, 1-2
Foraminifera slides, 1 per microscope (tape down to stage)
Shells and Corals, variety
Table, 1 6 foot
Table Cloth or butcher paper
Chair
Stepstools, 4-5
Set-Up
 Cover table with cloth or butcher paper.
 Set stools in front of tray and microscope stations/spots.
 Prepare trays with a layer of baking soda. Get all 6-8 trays ready. Used trays can be quickly
replaced with prepped tray.
 Fill test tubes with liquids. Place one pipette in each tube. Ensure test tube labels are
legible. Place test tubes (1 of each liquid per station) in tube rack. One rack in front of each
baking soda tray.
 Place, and tape down, foram slide on microscope stage. Focus microscope.
 Set shells and coral next to microscope.
 Line up cans/bottles of liquids (soda, lemon juice, water and vinegar), don’t place in order
of acidity. Place activity cards next to bottles.
 Have extra supplies handy, but not visible to the public.
Activity
 Invite visitors to do an experiment. Encourage guests to touch the shells/corals. Ask them to
describe them. Explain or describe what shells/corals are made of (calcium carbonate).
 Share that shelled animals, like the ones they looked at, are in danger of losing their ability to
make their shells. Changes in the ocean due to climate change (carbonate ions in the water are
becoming less available) make it tough to build their special shells (calcium carbonate).
 Describe how carbon dioxide gas from the burning of fossil fuels (coal, oil, etc) is ending up in
the ocean. This excess CO2 is slowly making the ocean more acidic. As a result, there are
fewer carbonate ions for animals to build their shells with.
 Ask if they have heard of stomach acid (or battery acid). Ask them if they know what stomach
acid does to the food we eat. Explain that acids are corrosive and dissolve things (like calcium
carbonate shells and baking soda).
 Introduce the liquids that they will be testing (vinegar, soda, lemon juice, water). Ask guests to
make a guess (hypothesis) about which items they think are more acidic or less acidic. Explain
that acids taste sour. Have guests put them in order from more acidic to less acidic.
 Have guests test their guess (hypothesis) by dropping the liquids onto the baking soda. Ask
them to look for evidence of the acids dissolving the baking soda.
 Have the guest share what they observed and compare it to their guess (hypothesis). Help reorder the liquids, if necessary.
 Remind guests that the baking soda is similar to the calcium carbonate in shells. Ask guests
what they think will happen to shell building animals (and the animals that eat them) if the
ocean becomes too acidic.
 Share or ask for possible solutions to reduce the amount of carbon dioxide that ultimately ends
up in the ocean. Reduce the burning/use of fossil fuels- drive less (reduce gas usage), use less
energy (reduce burning of coal and gas), etc.
Sample talk:
Invitation/Introduction: Do you want to do a science experiment? We are going to learn about
these shells. Do you know what animals make shells? What do all these shells and your bones
have in common? (Hint: Got Milk? Calcium). People need the mineral calcium for strong bones
just like these animals need it to make their shells or skeletons. These animals also need
carbonates (carbon) to make their shells. But scientists believe they won’t be able to get carbonates
from ocean water in the future because humans are changing the ocean’s chemistry. Whenever we
burn fossil fuels to drive our cars, or for energy in our homes and businesses, we release carbon
dioxide into the air. Much of the carbon dioxide released gets absorbed by the ocean. The
absorbed carbon dioxide makes the ocean more acidic. As a result there are less carbonate ions for
the animals to use. Have you heard of stomach acid or battery acid? Acids dissolve things like
calcium carbonate and baking soda. This experiment will help you see that a more acidic ocean is
bad news for shell-building animals.
Exploration/Concept Invention: These are all safe household items, but we have safety glasses for
our young scientists. On this plate is baking soda, which is very similar to the calcium carbonate
that marine animals use to build shells like these. In these test tubes we have some vinegar, plain
water, soda, and lemon juice. We are going to put these in order from more acidic to least acidic.
First, as a scientist, you must make a hypothesis, or guess. Which do you think is more acidic?
(Hint: acids taste sour) Then we will test our hypothesis by dropping the liquids onto the baking
soda. The strongest acid will fizz the most. (Let visitors see what happens when they drop the
liquids on the baking soda. Make sure they use only a few drops of each liquid.) Was your
hypothesis correct? Part of being a scientist is to prove a hypothesis wrong, so if you did that, you
succeeded!
Note: If you have very young children don’t ask them to make a hypothesis. Let them experiment
with the different liquids and then help them put them in order from more acidic to less acidic.
Reflection/Results: So we saw that lemon juice and then vinegar are the most acidic, while plain
water is actually not acidic at all. Sodas are also acidic, but not as much as vinegar/lemon juice. If
these stronger acids can dissolve baking soda, what do you think would happen to shell building
animals if the ocean becomes more acidic? What about the animals that eat those animals,
including people? The ocean is a major reservoir for storing carbon dioxide. Today the ocean is
30% more acidic than it was before we started burning fossil fuels like oil, gas and coal and
scientists tell us that in 100 years it may be too acidic for these animals to survive. Can you think
of anything you can do to help? If we all reduced the amount of energy we use, then less carbon
dioxide would end up in our oceans. What are some ways you can reduce your energy use to help
these animals?
Clean-Up
Pack up table and materials.
Rinse trays in sink with warm water.
Place caps on test tubes, preserving the water and vinegar.
Rinse out lemon juice and soda. Soda will go flat if not used within a few days and lemon juice
will go rancid if not refrigerated. Store lemon juice bottle (if opened) in refrigerator.
Background Information
Doney, Scott C. “The Dangers of Ocean Acidification” Scientific American March 2006: 58-65
“The Acid Threat” National Geographic Nov. 2007:110-111
Daily Demo for Climate Change Program - Ocean Acidification
Science Concept: Impact of Increased Carbon Dioxide
Objective:
The purpose of this demonstration is to help you see that a more acidic ocean is bad news for
shell-building animals.
Whenever we burn fossil fuels to drive our cars, or for energy in our homes and businesses, we
release carbon dioxide into the air. Much of the carbon dioxide released gets absorbed by the
ocean. The absorbed carbon dioxide makes the ocean more acidic (more H + ions). As a result
there are less carbonate ions (OH-) for the animals to use. Have you heard of stomach acid or
battery acid? Acids dissolve things like calcium carbonate and baking soda. So, animals that
make shells or carbonate skeletons may not be able to make them anymore.
Materials:

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Baking soda
Vinegar (acetic acid dissolved in
water)
Water
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2 Pipettes,
2 Test tubes and 1 holder
Safety glasses
Towels
Instructions:
 Fill test tubes with liquids. Place one pipette in each tube. Ensure test tube labels are
legible.
 Place test tubes (1 of each liquid per station) in tube rack. One rack in front of each baking
soda tray.
 Share that shelled animals are in danger of losing their ability to make their shells.
Changes in the ocean due to climate change (carbonate ions in the water are becoming
less available) make it tough to build their special shells (calcium carbonate).
 Describe how carbon dioxide gas from the burning of fossil fuels (coal, oil, etc) is ending
up in the ocean (carbon sink). This excess CO2 is slowly making the ocean more acidic. As
a result, there are fewer carbonate ions for animals to build their shells with.