Standard III: Students will understand the structure of cells and organisms.
Objective 2: Identify and describe the function and inter-dependence of various organs.
Indicator d: Describe how the cellular needs of organisms for food, air, and waste removal are met by tissues and organs (e.g., lungs provide oxygen to cells, kidneys remove wastes from cells).
Intended Learning Outcomes:
3d. Solve problems appropriate to grade level by applying scientific principles and procedures.

Background:
Students should have general understanding of cells and how their functions affect the organisms.
Students should have general knowledge of what a stomata of a leaf is and its function.

Time Required: 15-20 minutes

Summary: The stomata of plant cells allows materials to enter and leave the leaf of the plant. In general, the back side of a leaf has more stomata than the front side of a leaf. In this lab, you will test to see if this statement is true by using Cobalt chloride test paper. Cobalt chloride test paper is blue. When exposed to moisture, the paper turns pink.

Materials:

4 strips of Cobalt chloride test paper for each student or group of students working in pairs (can be purchased from a science catalog)
Scotch tape
a tree or plant with leaves
stop watch

Procedures:

• Go outside and find a tree with leaves
  
• Tape a strip of Cobalt chloride paper to each side of the leaf (it might be fun to use a leaf in the sun and a leaf in the shade. You could also try using different types of leaves from different types of trees.) Remember to leave the leaves you use attached to the plant!
  
• Record every 1 minute the color of the paper. (Is it still blue, part pink, all pink, etc.?)
  
• Create a table to show results.
  

Sample Table:

Visit the Utah State 7th Grade Integrated Science Core Curriculum Page.
Updated August 27, 2001 by: Glen Westbroek

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