The assignment pre-tests student understanding of the CCD, lysocline, calcareous ooze, and the deposition of marine sediments near mid-ocean ridges and ocean basins.

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We now know how to analyze pure compounds, but what if we have a mixture? Spectrophometry becomes quite complex when dealing with multiple species of compounds at once. In order to purify a compound we can separate if from a mixture based on its intrinsic chemical properties. Remember that fluorescein is negatively charged at a pH above pKa of the carboxyl group. We can take advantage of this fact and use its attraction to positive charges to separate it from other molecules. In ion-exchange chromatography, we will use a stationary phase with a positive charge, allowing negatively charged molecules to bind and positively charged species to flow through. We can then disrupt this interaction and retrieve our now-purified molecule, and use spectrophotometric analysis of our purified fractions to determine how well we were able to separate our molecules.

A primary objective of marine science classes is to learn the location and formation of ocean sediment types. Nearly 50 years of scientific ocean drilling has produced a tremendous scientific collection of cores from the global ocean floor. In addition, there are large online databases and related publications that have a wealth of associated information to supplement physical cores. Here we created a virtual marine core collection that provides exemplars of the primary ocean sediment lithologies, along with links to expedition reports and datasets, and tips for making requests for real core samples to use in education.

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Previously, we showed how different compounds absorb light. The chemical structure of a molecule determines exactly how much light it absorbs, as well as which wavelengths are absorbed. It stands to reason then, that by removing an atom from a molecule, we can change the way it absorbs light. In this experiment, we will relate these two concepts by measuring the absorbance of a molecule under acidic and basic conditions. The changing pH will allow us to find how strongly a specific hydrogen is attached to our molecule, and we will observe how the changing chemical structure affects the observed absorbance. Afterwards, using mathematical analysis, we can experimentally determine the pKa, or affinity of our hydrogen to our parent molecule.