*** Attention Students ***
Use the text box at the bottom of the page to submit your work.
PLEASE READ THIS ENTIRE PAGE BEFORE BEGINNING THIS ASSIGNMENT
In this lesson you will perform experiments, develop conclusions, and write a report of your procedure and findings.
If you work from any outside sources, you will be responsible for citing all sources of your information. If you do not cite your sources, you will not get full credit for the project.
Introduction:
Plants use colored molecules (pigments) to collect light so that they can make food and to communicate with animals through their flowers and fruit. Many of the pigments can be removed from plant cells and dissolved in water or some other liquid. Many pigments that will not dissolve in water will dissolve in isopropanol, which is the main component of rubbing alcohol. This procedure can be used to extract pigments from plants, using water and isopropanol at the same time.
Materials:
- some leaves from a green leaf specimen
- some leaves or flower petals from a specimen that is not green (red cabbage will work here)
- samples of a root plant, such as carrots or beets
- samples of a berry or fruit
- four thick ziploc bags
- salt
- strong saltwater mixture (make it by adding salt to warm water and stirring--keep adding salt until it no longer dissolves)
- isopropanol (rubbing alcohol)
- Paper towels
- 4 clear containers (glass or clear plastic)
Procedure:
Follow these instructions and keep a written record of precisely what you do and do not do. The record should be detailed enough that someone else could perform the same procedure just using what you have written.
You will perform this procedure on each of your four specimens.
- Chop up a handful of the leaves (or whatever you collected) into small pieces. The better you chop them up, the better this experiment works. Put them in a thick plastic bag (freezer bags work well) along with a teaspoon of salt. The salt will help to grind up the leaves, so that the plant cells break open and release their pigments.
- Add some salt water mixture and some isopropanol to the bag. About an ounce of each will be fine--you don't need to be too precise here. Stir the mixture, feel free to mash up the leaves some--the idea is to make the pigments dissolve.
- Place a paper towel into one of the clear containers, and pour your mixture into the towel. You'll need to be able to pick up the paper towel by its edges to let the liquid drip through into the container. The solid material will stay in the paper towel, leaving only the liquid in the container. (You'll do this for all four specimens.)
- Allow the contents of the containers to settle into layers.
Analysis Questions:
- Make a table, with your specimens listed across the top and the layers on the left. Fill in the colors you find for each specimen, and submit this table as part of your report.
| specimen 1 | specimen 2 | specimen 3 | specimen 4 |
|---|
| isopropanol | | | | |
|---|
| water | | | | |
|---|
- For each plant type, where did you find more pigment, in the upper or lower layer of liquid? Or did you find different colors in each layer?
- Water is denser than isopropanol, so the water layer will always be below the isopropanol layer if they are both in the same container. What does this tell you about the make-up of the pigments for each specimen?
What Do I Need To Submit?
All of the following should be submitted at one time--DO NOT submit partial reports, they will not be accepted.
- Submit to your teacher a report of your procedure and the data you collected. Use paragraphs with complete sentences and proper English grammar.
- Submit your data analysis to your teacher. Be sure that your analysis addresses the questions and directions listed in the instructions above. Remember to submit your table of layers, but also remember to use this information in your report. Also record any other conclusions you have reached. Use paragraphs with complete sentences and proper English grammar.
- Part of the challenge of a lab is figuring out how best to organize your information and submit your findings. Remember this is a report, not just a listing of what happened.
Grading for this lesson:
- 10: You can have no errors (factual, spelling, punctuation, capitalization, wrong word, etc),
within the second revision of this report. Answers are correct, complete, and clear; all report requirements have been met.
- 9: You can have 1 or 2 errors (factual, spelling, punctuation, capitalization, wrong word, etc) on the second revision of the report or you can have no errors on the third revision. Answers are correct, complete, and clear; all report requirements have been met.
- 8: You can have 1 or 2 errors on the third revision of this report or you
can have no errors on the fourth revision. Answers are correct, complete and clear; all report requirements have been met.
- 7: You can have up to 5 errors. Report is complete and clear; all
report requirements have been met.
- 6: You can have up to 8 errors. Report is complete and
clear; all report requirements have been met.
- 5: Plagiarism – purposeful or mistaken which will lower your final grade for the course (so be very careful when posting your work!); lack of effort, disrespect, or attitude (we are here to communicate with you if you don’t understand something); or 9 or more errors; or report requirements have not been met.
Also be aware that you will have a chance to revise your work. More than 2 revisions
will result in a lower grade, so read the directions carefully and make sure you meet the requirements.
No lesson is complete without the approval of the instructor, and all revisions must be completed before a grade is assigned. No grade will be given for incomplete work.
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