Overview
Because weather in different areas averaged together for years creates the regional climate, and regional climates averaged together yield the global climate, what happens in our own backyard can influence what happens around the world. So, when you burn carbon dioxide in the form of gasoline for your family car, coal or natural gas for heating or cooling your family’s house or apartment, or use energy to watch T.V. or play on the computer, the gas is released into our atmosphere. Some of it gets absorbed by the ocean, which acts as a carbon ‘sink’ and helps prevent greenhouse gases from warming the planet too much.
Introduction
This activity explores what happens to oceans which have absorbed much more carbon dioxide than they normally contain as a result of human carbon emissions.
Grade Level
K-5, 6-8
Learning Objectives
Students will be able to explain what happens to carbon dioxide when it enters the atmosphere.
Lesson Format
This activity can be done indoors!
Time Required
30min - 1 Hour
Credits & Contact Info
Trisha Smrecak and Caroline Boyajian
Paleontological Research Institution, 1259 Trumansburg Rd., Ithaca NY 14850
climate@priweb.org
Instructions & Materials
Materials
- Large glass container (a coffee pot or clear vase works well)
- Water
- Salt
- Antacid tablet
- Bromophenol blue (acid base indicator liquid available on science education supply stores)
- Dry ice
Instructions
- Make an ‘ocean’ by filling a glass container with water and adding a pinch of salt.
- Add a few drops of bromophenol blue, which will turn yellow if acidic and blue if not. It should start out blue.
- Add a small chunk of dry ice (cooled and compressed carbon dioxide) to the ‘ocean’ and observe what happens (the ocean turns yellow).
- Explain that as the dry ice sublimates (goes from a solid to a gas), the carbon dioxide bubbles get absorbed by the ocean, which makes it more acidic and changes the color of the pH indicator.
- Try the experiment again, except instead of placing dry ice in the ‘ocean,’ use a straw to exhale carbon dioxide into the water. You should see the same color change.
- Place an antacid tablet in the acidic ‘ocean.’ Observe what happens.
Discussion
Earth’s oceans are a natural carbon sink, meaning that they can store carbon so less is able to escape into the atmosphere and ‘thicken’ our greenhouse gas blanket. However, humans have emitted a lot of carbon dioxide into the atmosphere, and the oceans are having trouble keeping up. As a result of taking in our extra carbon dioxide, the overall chemistry of the ocean is changing. When carbon dioxide dissolves in seawater, it produces a weak acid called carbonic acid. So with more carbon dioxide available in the atmosphere to dissolve in the ocean, the ocean is becoming more acidic, just like the ‘ocean’ in this activity.
Many organisms that live in the ocean are vulnerable to changes in the ocean chemistry, and can only live in a narrow pH (acid/base) range. Especially at risk are organisms that secrete a shell made of calcium carbonate, like some corals, mollusks (clams, gastropods/snails), and microscopic organisms.
In your ‘oceans,’ a simple antacid tablet brought the pH level of the ocean back up so it was no longer acidic. It is not as simple to correct the pH balance of our Earth’s oceans, so changing the acidity of the oceans can create extinction events in the ocean, too.
Extensions
CoCoRaHS Extension Ideas:
Learn about other aspects of water quality in lakes, rivers, and oceans that can contribute to the health of the organisms living within those bodies of water. Create a water quality measuring kit (including pH indicators, turbidity indicators, water flow monitors, etc.) and go out to a local water body. Measure the health of the water body and, if it is not as healthy as it could be, discuss ways in which human activity could improve or further degrade the body of water. Would a change in climate affect the health of this water body? Why or why not?