- Central Question:
How does a decrease in the pH of seawater affect the calcium carbonate shells of animals? - Overview of Experiment:
Shelled organisms that create calcium carbonate
skeletons are threatened by the drop in ocean pH (rise in ocean acidity)
related to increased atmospheric carbon dioxide levels. Increasing
acidity/lowered pH in ocean water not only causes the shells to dissolve,
but it reduces the availability of carbonate ions – which animals use to
build their shells and skeletons.
Hypothesis:
If I blow carbon dioxide CO2 to any kind of water, then it will change the pH (acidity).
Materials Checklist
100 mL Saltwater - Thermometers
500 mL beakers - Hot Plate
straws - Ice
timer - disposable pipet
- 100mL Saltwater with indicator solution
0.6mL tube with 0.2mL of (to compare before/after)
universal indicator solution
Safety Goggles
Pre- lab questions:
1. What gas are you blowing into the water?
2. What happens to the gas when you blow it into the water?
3. How are you measuring change in the water during this lab?
4. What does measuring the pH of the water tell us?
5. After studying the reactions above, how do you think carbonic acid will affect the pH of salt
water?
Analysis/Discussion of Data
1. When you immersed the shells in vinegar how did you know that a reaction was
happening?
When we put the shells in our acidic substances we noticed that C was bubbling like crazy and that gave us a
sign that a reaction was happening.
2. How did observing the shells in vinegar relate to how animals are affected by
a lower pH of ocean water?
Just as the shells were bubbly and disintegrating, the animal's tissues
and sins dissolve in the acid just as if you were to pour bleach on your hand,
it burns and irritates, same as the marine animals.
3. How would shelled organisms be affected by a lower pH of ocean water?
Young fish and immature stages of aquatic insects are extremely sensitive to pH levels below 5 and may die at
these low pH values. High pH levels (9-14) can harm fish by denaturing cellular
membranes. Low pH levels accelerate the release of metals from rocks or sediments in the stream. These
metals can affect a fish’s metabolism and the fish’s ability to take water in
through the gills, and can kill fish fry.