Title: In Class Activity: Demonstrating osmosis (Part 1 and Part 2)
Course: Biochemistry > Section: Week 8 - Unit 3_2: Membrane Transport Mechanism

Purpose: To demonstrate osmosis in action

Over to you:  In pairs, students do an experiment using mushed potatoes

Activity

To experiment with osmosis using potatoes, you will need two shallow dishes, a potato, knife, water and salt.

Fill both of the dishes with an inch of water. Add two tablespoons of salt to only one dish, while leaving the other plain. (Be sure to label which dish is plain and which has salt added to it.)

Slice the potato lengthwise, so that you end up with several pieces that are flat on both sides.

Place a few pieces of potato into the plain water, and an equal number of pieces into the salty water.

Allow the potatoes to sit for 20 minutes, then come back and allow the students to make their observations, and explain to them what happened.

The potatoes that were in the salt water now appear mushy because of osmosis. Due to the higher concentration of salt in the water surrounding the potatoes, the water moved from the potatoes and into the surrounding water to balance it out.

This left the potatoes in the salt water mushy, while the ones in the plain water have no change to their appearance