4 March Science 8 Chromatography

Mindful moment.

Review previous class (what structures were we looking for–in the leaf, in the photosynthetic plant cell? why?)

See board.

Anticipate Summative project on supporting the claim of photosynthesis. To be described on Wed. Due the following Tuesday by the end of class.


Today’s activity provides an experience with a crucial technique in the understanding of photosynthesis. The technique uses the varying solubility of different molecules (the plant pigments) in a solvent. The solvent moves up a strip of paper by capillary action. See reference: < https://water.usgs.gov/edu/capillaryaction.html  >.The different molecules move at different rates. Separation is one part of discovering the reaction pathways in complex processes. How did Benson and Calvin separate the molecules involved in the numerous photosynthesis reactions? After separation, analysis is carried out to describe the properties, create models, name, and identify the products of the separation. What do you think are the techniques used for such analysis?

In science it is important always to ask–How do we know? The next task is to describe the evidence and to explain how the evidence is linked to claims. Connecting claims with evidence is what is meant by the phrase scientific argument. Your summative assessment on photosynthesis will involve organizing the evidence both from historical experiments and from your own first hand activities, experiences, and experiments and linking the evidence to the (over)simplified claim of photosynthesis. Data that have been analyzed and interpreted in light of an hypothesis, theory, claim become evidence.


Follow instructions for the extraction and separation of plant pigments through paper chromatography. See board. Listen closely to verbal instructions. Watch demonstrations of techniques. Follow all safety guidelines. Record all procedures (verbal descriptions, diagrams-sketches, photos). Record all observations.


  • What do Chlorophyll and other pigments have to do with the claim of photosynthesis?
  • What does the technique of paper chromatography have to do with the claim of photosynthesis?
  • (In other words, why would we conduct this activity at this time in our study of photosynthesis? What do you learn?)

This image provides an idea of the proper set-up:


See the image from someone’s experiment: http://socrates.acadiau.ca/COURSES/BIOL/REEKIE/1113/photo/cpaper.gif

There are a number of articles on the history of chromatography. Here is one: history chromatography

More on procedures for chromatography–also interpretation of results:



See–Why aren’t all plants black? by Physics Girl–excellent youtube science channel:

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