Off Base - Acidity of Oceans

Tuesday 2:50pm-3:10pm TSU - Humphries: 221
Teaching Demonstration Part of Tuesday Teaching Demos

Leader

Cheryl Manning, Evergreen High School

Demonstration

Using simple household chemicals, I will demonstrate gas dissolution into water, and building on what students know about pH and acids and bases, I will introduce chemical equilibrium, the buffering properties of seawater, and ocean acidification.

Abstract

The teaching demonstration introduces gas dissolution into water, chemical equilibrium, the buffering properties of seawater, and ocean acidification. Inspiring students to ask questions from which they will design an investigation on how increasing atmospheric carbon dioxide levels may affect ocean pH and the organisms that depend on stable ocean chemistry to calcify skeletal material. Working with distilled and synthetic seawater, pH indicator solutions, and dry ice, I will introduce Le Chatelier's Principle, equilibria, buffered solutions, and the carbonate Bjerrum Plot.

Context

A version of this activity happens on days 8-9 of a 10 day unit on the History of Oceans and Atmosphere. ​​Students have learned about how scientists know about the history of the Earth's oceans and atmosphere and will apply their understandings to compare current changes in atmospheric CO2 levels to what is know about the sudden changes that occurred during the Permo-Triassic Extinction. (https://cleanet.org/clean/literacy/teach_guidance/oceans_atm.html)

Why It Works

The activity is fun and firmly grounds students in basic chemical principles of buffered solutions, equilibrium, acids and bases, and diffusion of gases into liquids. The interconnection between the Earth Sciences and Chemistry is clear and provides a good example of why students should take chemistry to understand the Earth. Embedded in the History of Oceans and Atmosphere unit, the activity also provides students with the background that they need to see the correlations between the Permo-Triassic Extinction and the Anthropocene.

Resources

EER19_Teaching Demo.pptx (PowerPoint 2007 (.pptx) 5.5MB Jul16 19)