Student Exploration: Osmosis
Vocabulary: cell membrane, concentration, diffusion, dynamic equilibrium, osmosis, semipermeable membrane, solute, solvent
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. Suppose you were trapped on a desert island with no sources of fresh water. Should you drink water from the ocean? Explain why or why not.
2.What do you think would happen if you watered your houseplants with salt water?
A cell membrane is a thin “skin” that surrounds a cell. It is a semipermeable membrane, which means that some particles pass through the membrane easily while others cannot.
The Osmosis Gizmo™ portrays a cell (red square) in a solution of purple solute particles dissolved in green solvent particles. Press Play ( ) and observe.
1. Which particles can pass through the cell membrane?
2. Which particles cannot pass through the cell membrane?
3.Click Reset ( ), and then click Play again. What do you notice about the size of the cell?
Question: How do solute concentrations affect the volume of a cell?
1. Observe: Use the Solute outside slider to change the concentration of solute particles outside the cell. Click Play. In each case, focus on whether the cell gets bigger or smaller.
A. In what situation does the cell get larger?
B. In what situation does the cell get smaller
Calculate: The concentration of a solute is the amount of solute particles in a given amount of solvent. To calculate percentage concentration, divide the number of solute particles by the total number of particles (solute + solvent), and then multiply by 100: