Name: ________________________________________________________
P: _____
Save The Shells!
Background
Have you ever sipped a drink that tasted sour? The acid in what you drank caused the sour taste.
What is acid? Generally, it is an aqueous (water) solution that contains hydrogen ions. A hydrogen ion (H+) is a
hydrogen atom with the electron removed. Because the electron is not present, the hydrogen ion has a
positive charge.
The positive charge of the hydrogen ion makes it chemically active. One example would be the chemical action
of the hydrogen ions on your taste buds, producing the sour taste.
Acids can be strong or weak, depending on the concentration of hydrogen ions. Vinegar is a weak acid, having
a low concentration of hydrogen ions. The high concentration of H+ in a strong acid, such as sulfuric acid, can
eat away metal!
Scientists have a numerical scale for the relative strength of acids
called the pH scale. The H in pH refers to the concentration of
hydrogen ions present in the solution. The p comes from potenz, a
German word referring to power or potential.
The pH scale ranges from 0.0 (very high concentration of hydrogen
ions) to 14.0 (very low concentration of hydrogen ions). The pH
range of 0.0 to 7.0 is called acidic, and the range from 7.0 to 14.0 is
called basic.
Liquids with a low pH value are highly acidic and have a sour taste.
Liquids with a pH of 7.0 have a neutral taste. Pure water has a pH of 7.0. Liquids with a pH value that is higher
than 7.0 have a bitter taste. Such liquids are called bases.
A pH indicator is a substance whose change of color indicates a change of pH in an aqueous solution.
Shells serve as a protective structure for both marine and terrestrial organisms. Marine ecosystems that
depend upon calcium carbonate to make shells, such as coral reefs or oyster beds, can be impacted by
changes in ocean pH due to increased carbon dioxide. In experimental conditions under very high levels of
CO2, shells of clams, oysters, corals, snails and urchin shells dissolve. If these organisms are unable to build or
repair shells, due to increased acidification caused by human activities, they will likely cease to exist in these
environments.
Materials
 Pieces of empty clean chicken eggshell (these are abundant, calcified shells and serve as a proxy for
marine shells)
 Lemon juice, vinegar, cola, ammonia, water, soap and other household solutions
 pH test strip, pH probe, or red cabbage juice indicator
 A small dish for each sample
 Medicine dropper or plastic pipette
 Scale (if you choose to measure the changes)
 Magnifying lens
Name: ________________________________________________________
P: _____
Question:
What will happen if you put a piece of eggshell in cola, water, soap, lemon juice, vinegar, and ammonia?
Which solution will have the greatest effect on the shell?
Commit to a prediction:
The eggshell will (dissolve, break, change color, change size, stay the same…)
_________________________________________________________________ when put in cola.
The eggshell will ____________________________________________________________________________
when put in lemon juice.
The eggshell will ____________________________________________________________________________
when put in vinegar.
The eggshell will ____________________________________________________________________________
when put in ammonia .
The eggshell will ____________________________________________________________________________
when put in water.
The eggshell will ____________________________________________________________________________
when put in soap.
The _______________ solution will have the greatest effect on the shell.
Explain your thinking.
The ______________________ solution will have the greatest effect on the shell, because…
Observations:
Part 1: Procedures
1. Use pH strips to identify the acidity of each solution, or get this information from your teacher.
2. Put a separate piece of shell into each small dish. Keep one piece of shell in a dish on its own (with no
liquid) as a control.
3. Use the dropper to place a few drops of selected liquid on the shell piece. Use a different piece of shell
for each liquid. Label the dish with the type of liquid you used.
4. Watch what happens for 5-10 minutes.
5. Write down observations as you notice changes in the shells.
pH of Cola: ______
pH of Water: _____
pH of Lemon Juice: ______
pH of Vinegar: _____
pH of Ammonia: ______
pH of Soap: ______
Name: ________________________________________________________
Part 2: Observations
COLA
LEMON JUICE
VINEGAR
WATER
P: _____
AMMONIA
SOAP
Which liquids react with the shell first?
From your observation on the eggshell, what might be some consequences of ocean acidification for animals
with shells?
Scientific Explanation
Claim: The ____________ solution had the greatest impact on the shell.
Evidence: The evidence that supports my claim is (use observations from above)….
Reasoning: How does the evidence above ALLOW you to claim that the this particular solution had the greatest
impact on the shell?
Name: ________________________________________________________
P: _____