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Instructions by John W. Fedors
Crinkled Dialysis Tubing
Dialysis tubing can be used to simulate cell walls/cell membranes. The microscopic pores provide a passageway for select sized molecules to diffuse from a greater to a lesser concentration; passive transport of larger molecules is inhibited. Yes, you have a semipermeable membrane. Water and other small molecules have the ability to diffuse both ways and to establish an equilibrium. The equilibrium may be measured by changes in: concentrations, osmotic pressure, color, volume, and mass. Activities can be designed to be specific or a combination of these changes.
The use of 'Serpent Skin' provides tubing which is much easier to use than dialysis tubing. The usual dialysis tubing is flat and has to be wet to use. The open tubing makes it easier to fill with a variety of materials, especially dry.
The activities which you can develop using 'Serpent Skin' is limited only by your comfort level of exploration. The expense of teacher/student designed explorations may also be a challenge.
Exploration Purpose: Demonstration of Water Pressure
In But Not Out
Water Molecules Pass Through a Variety of Membranes
There are conditions in nature which retain water and build pressure on membranes.
Design an exploration that may demonstrate how water molecules may be collected in a porous container and be kept there.
Procedure: (This is how it might be set up)
Water Rock Volcano
Serpent Skin is Forced to Erupt Water Rocks
Water pressure may force larger molecules to erupt through a designed opening.
Design an exploration that will demonstrate water pressure on crosslinked polyacrylamide.
Slow Iodine Clock
Molecules Vary in Size and Larger Molecules are Easier to Contain
A solution containing iodine molecules can be used to demonstrate that they are constantly moving to attain equilibrium.
Design an exploration that will demonstrate the movement of iodine molecules from an area of higher concentration to one of lower concentration.
In, Up, and Out
Serpent Skin is Selective to Concentrations
The less concentrated a water solution, the less solute, the quicker it moves toward higher concentrations and more solute.
Design an exploration that will demonstrate movement of both solvent and solute through membranes at different rates.
Hassle-Free (crinkled dialysis tubing) simulates a cell wall/membrane. The
microscopic pores in the cellulose tubing produce a physical selection barrier, a semipermeable
membrane. The microscopic pores provide a passageway for select-sized
molecules to diffuse from a greater to a lesser concentration and inhibit larger
molecules from diffusing. Water and small molecules have the ability to diffuse both
ways and to establish a concentration equilibrium.
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Students can use Serpent Skin in an investigation to describe and classify different kinds of materials by their observable properties.
Students can use Serpent Skin in an investigation to develop a model to describe that matter is made of particles too small to be seen without magnification.
Students can use Serpent Skin in an investigation to develop models to describe the atomic composition of simple molecules and extended structures.
Students can use Serpent Skin to conduct an investigation to provide evidence that living things are made of cells, either one cell or many different numbers and types of cells.
Students can use Serpent Skin to develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function.
Students can use Serpent Skin as part of the evidence to support an argument for how the body is a system of interacting subsystems composed of groups of cells.
Students can use Serpent Skin as part of an investigation to gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories.
Students can use Serpent Skin in an investigation to predict properties of elements. Students can use the Periodic Table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms.
Students can use Serpent Skin in an investigation to communicate scientific and technical information about why the molecular-level structure is important in the functioning of designed materials.
Students can use Serpent Skin to construct an explanation and models of cells based on evidence for how the structure of DNA determines the structure of proteins that carry out the essential functions of life through systems of specialized cells.
Students can use Serpent Skin to develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions with multicellular organisms.
Students can use Serpent Skin to develop a model to illustrate how photosynthesis transforms light energy into stored chemical energy.
Students can use Serpent Skin in an investigation to see density in action. The heat sensitive material is a polymer.
Students can draw on Serpent Skin during an investigation to illustrate how the shape of an object helps it function as needed to solve a given problem.
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