Student Exploration: Osmosis

Name: Date: Student Exploration: Osmosis Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. 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 freshwater. Should you drink water from the ocean? Explain why or why not. No, because it will cause our cells water to exit the cell and go into the saltwater this is a Hypertonic solution. 2.​ What do you think would happen if you watered your houseplants with salt water? They will also shrivel and eventually die due to plasmolysis where the plant will release its water from the large central vacuole, due to the fact that the plant’s water is fresher than the salt water. Gizmo Warm-up 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? The solvent can pass through the cell membrane. 2.​ Which particles cannot pass through the cell membrane? 3.​ Click Reset ( The Solute can’t pass through. ), and then click Play again. What do you notice about the size of the cell? The cell size increases as time passes as more solvent passes through. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved Activity A: Get the Gizmo ready: ●​ Click Reset. Set the Initial cell volume to 40%. ●​ You will need a calculator for this activity. Observing osmosis 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? When there is less solute B.​ In what situation does the cell get smaller? When there is more solute 2.​ 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: % concentration = (solute ÷ total particles) × 100 Select the DESCRIPTION tab. Click Reset. Set the Solute outside to 10 and check that the Initial cell volume is 40%. (Note: The cell volume is expressed as a percentage of the container size.) A.​ How many solute particles are found inside the cell? 5 Outside? 10 B.​ How many solvent particles are found inside the cell? 94 Outside? 92 C.​ What is the total number of particles inside the cell? 99 Outside? 102 D.​ What is the % concentration of solute inside the cell? 5.05% E.​ What is the % concentration of solute outside the cell? 9.8% 3.​ Observe: Click Play, and observe the numbers shown on the DESCRIPTION pane. How does each number change over time? Write “increases,” “decreases,” or “stays the same” (or “same”) in each space. ●​ Solute particles inside? stays the same ●​ Solute particles outside stays the same ●​ Solvent particles inside? decreases ●​ Solvent particles outside? increases ●​ Solute concentration inside? increases ●​ Solute concentration outside? decreases ​Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved 4.​ Observe: Wait until the numbers are not changing very much. What do you notice about the solute concentrations inside and outside of the cell? The solute concentrations inside and outside the cell are much closer because the cell is working toward equilibrium. This situation is called dynamic equilibrium. 5.​ Experiment: Click Reset. Check that the Solute outside is 10 and the Initial cell volume is 40%. To calculate the solvent concentration, divide the number of solvent particles by the total number of particles, and then multiply by 100. (Note: The Gizmo only displays the solute concentrations.) A.​ What is the solvent concentration inside the cell? 6.49% B.​ What is the solvent concentration outside the cell? 8.06% C.​ Where is there a higher solvent concentration? outside the cell D.​ Click Play. Do most of the solvent particles move into or out of the cell? (Hint: Does the cell expand or shrink?) Most of the solvent particles move out of the cell. The cell shrinks. 6.​ Experiment: Click Reset, and set the Solute outside to 1. A.​ What is the solvent concentration inside the cell? 3.76% B.​ What is the solvent concentration outside the cell? 1.69% C.​ Where is there a higher solvent concentration? inside the cell D.​ Do you think the cell will get larger or smaller? larger E.​ Click Play to confirm your predictions. Were you correct? Yes 7.​ Summarize: You have observed examples of osmosis—the diffusion of a solvent (such as water) across a semipermeable membrane. Summarize what you have observed by filling in the blanks in the following paragraph: During osmosis, solvent particles move from an area of lower higher concentration to an area of concentration. When there is a higher concentration of solvent particles inside the cell, most solvent particles will move outside of the cell and the cell will get small er . When there is a higher concentration of solvent particles outside the cell, most solvent particles will move into ​Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved the cell and the cell will get larger . Get the Gizmo ready: Activity B: Effect of cell volume ●​ Click Reset. ●​ Set the Solute outside to 5. ●​ Set the Initial cell volume to 40%. Question: How does changing the cell volume affect solute concentrations? 1.​ Experiment: Select the BAR CHART tab, and turn on Show numerical values. A.​ Based on solute concentrations, do you expect the cell to swell or shrink? Swell B.​ Click Play, and observe. Was your prediction correct? Yes 2.​ Observe: Click Reset. Move the Initial cell volume slider back and forth. How does the initial cell volume affect the solute concentrations inside and outside the cell? When the initial cell volume decreases, the solute concentration inside the cell increases while decreasing inside the cell. When the initial cell volume increases, the solute concentration outside the cell decreases while inside the cell increases. 3.​ Experiment: With the Solute outside set to 5, predict whether the cell will swell, shrink, or stay the same with each of the following Initial cell volume settings. Then use the Gizmo to check each prediction. Predictions: 20% swell 50% same 60% shrink Actual results 20% swell 50% same 60% shrink 4.​ Analyze: Why do solvent particles flow into the cell when the initial volume is below 50%? Solvent particles flow into the cell when the initial volume is below 50% because there is more solvent on the outside than in the inside more solvent particles are able to flow into the cell. 5.​ Extend your thinking: In the Osmosis Gizmo, the cell is placed in a very small chamber. Suppose a cell is placed in a large container of water with a very low solute concentration. What do you think would happen? Explain your answer. When there is a low solute concentration the cell will increase since the water is entering the cell where there is a lower concentration allowing the cell to swell. Water moves from high to low concentration due to the water on the outside having a higher percentage of water than the inside, since it is not 100% water, the water will enter the cell to reach equilibrium. This is a hypotonic solution. ​Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved