Lab 4: Ocean Acidification
Week of Tue, Sep 22 · lab closes Mon, Sep 28 · 30 points
This lab's items
- Data Collection (due 9/28) + Lab Write Up (due 10/5)30 pts
Exact due times are in Canvas. Late assignments are not accepted without a valid, documented reason. Make-up assignments are not given without valid documentation.
Know these cold
- Oceans absorb approximately 30% of the CO₂ humans emit each year. This absorption is slowing climate change but acidifying the ocean: since industrialization, average ocean pH has dropped from 8.2 to approximately 8.1 — a 30% increase in hydrogen ion concentration (pH is logarithmic).
- Chemistry of acidification: CO₂ + H₂O → H₂CO₃ (carbonic acid) → H⁺ + HCO₃⁻. The released H⁺ ions lower pH and react with carbonate ions (CO₃²⁻) that marine organisms use to build shells and skeletons.
- Organisms most at risk: mollusks (oysters, clams, mussels), corals, sea urchins, pteropods (sea butterflies), and some plankton. Their calcium carbonate (CaCO₃) shells dissolve in acidic water — CaCO₃ + 2H⁺ → Ca²⁺ + H₂O + CO₂.
- In your lab, you are simulating this chemistry with household liquids. The five test liquids (vinegar, cola, lemon/lime juice, baking soda solution, and one of your choice) represent different pH values. The solid materials (eggshells, seashells, chalk, chicken bones, etc.) model carbonate structures.
- Controls in your experiment: keep liquid volume, container size, temperature, and observation time constant across all six containers. The only independent variable should be the type of liquid (pH level).
- Predicted outcome based on chemistry: materials with carbonate structures should show more visible reaction (fizzing, softening, surface degradation) in acidic liquids (lower pH) than in neutral or basic liquids.
- Ocean acidification impacts food webs: pteropods are key prey for salmon, whales, and seabirds. Shell-forming plankton form the base of many marine food chains. Acidification that dissolves their shells cascades up the food web.
- Possible sources of error in your lab: room temperature variation, differences in contact surface area, impurities in liquids, differences in how tightly lids sealed the containers. Identify which errors are random and which are systematic.
Discussion and forum — how to show up
Netiquette from the syllabus: address ideas, not people. Complete sentences, correct spelling. Personal matters go to email, never the board.
Meerk's quiz — open the Lab 4 gate
10 questions, no time limit. 85% on your first attempt in a 24-hour window opens the gate. Retakes inside the window are practice — they help you learn, they don't count. Work alone; the point is to know it, not to have seen it.
Dinner Table Question
Ask at home: If ocean acidification dissolves coral reefs in your lifetime, what do you think the ocean will look and feel like — and what will people living near the coast lose?
En español: Si la acidificación del océano disuelve los arrecifes de coral en tu vida, ¿cómo crees que se verá el océano — y qué perderán las personas que viven cerca de la costa?