Osmosis in Potato Strips - Bio Lab

Summary

This educational video demonstrates the process of osmosis using potatoes and solutions of varying salt concentrations. It explains how water moves from an area of higher water potential to lower through a semi-permeable membrane, as seen in plant roots absorbing water. The experiment involves measuring changes in potato strip lengths after immersion in solutions with different salt concentrations, illustrating the concepts of hypertonic, hypotonic, and isotonic solutions. The results are graphed to show the relationship between salt concentration and water movement, highlighting the scientific principles behind osmosis.

Takeaways

• 💧 Osmosis is a diffusion process that specifically involves the movement of water and other solvents across a semi-permeable membrane.
• 🌊 Seawater has a lower water potential compared to pure water due to the presence of solutes like salt.
• 🌱 Plant roots absorb water by osmosis, as rainwater has a higher water potential than the water inside the roots.
• 🥔 A laboratory experiment can demonstrate osmosis using potato strips and solutions of varying salt concentrations.
• 🔍 The experiment requires 18 potato strips, each standardized to a length of 6 centimeters for consistency.
• 🧪 Six solutions are prepared with salt concentrations ranging from 0 to 5 grams per 100 milliliters, in one-gram increments.
• ⏱️ The potato strips are immersed in the solutions for 20 minutes to observe the osmotic effects.
• 📏 After 20 minutes, the strips are measured for any changes in length, indicating water movement into or out of the strips.
• 📊 The data is organized into a table and graphed to show the average change in length of the potato strips against the salt concentration.
• 📉 The graph reveals a downward curve, indicating that lower salt concentrations cause an increase in strip length due to water intake (hypotonic solution), while higher concentrations cause a decrease in length due to water loss (hypertonic solution).
• 💡 The point at which the graph crosses zero indicates an isotonic solution, where there is no net movement of water across the membrane, occurring at approximately 1.4 grams of salt per 100 milliliters.

Q & A

What is osmosis?

Osmosis is a special type of diffusion that applies to water and other solvents, involving the net movement of water from an area of higher water potential to an area of lower water potential through a partially permeable membrane.

Why is there less water present in a liter of seawater compared to a liter of pure water?

There is less water present in a liter of seawater because some of the volume is occupied by salt, making the water potential lower due to the presence of solutes.

How does osmosis explain plant roots taking in water?

Osmosis explains plant roots taking in water because rainwater entering the soil has a higher water potential than inside the roots, causing water to move into the roots.

What materials are needed to demonstrate osmosis using potatoes in a lab setting?

To demonstrate osmosis using potatoes, you need potato strips, a cork board, a knife, six test tubes, a balance, and solutions of varying salt concentrations.

How are the potato strips prepared for the osmosis experiment?

The potato strips are prepared by pushing them through a cork board to create uniform strips, then trimming them to 6 centimeters in length and removing the skins.

What are the steps to create the solutions for the osmosis experiment?

The solutions for the osmosis experiment are created by weighing out 1 gram of salt and adding it to 100 milliliters of water to make a 1 gram per 100 milliliters solution, and then preparing solutions from 0 to 5 grams per 100 milliliters in one-gram increments.

How long should the potato strips be left in the solutions during the experiment?

The potato strips should be left in the solutions for 20 minutes to observe the effects of osmosis.

What observation can be made about the potato strips after 20 minutes in the solutions?

After 20 minutes, the potato strips in more concentrated solutions will be softer, indicating water loss, while those in lower concentrations will be more turgid, indicating water uptake.

How is the data from the osmosis experiment processed?

The data is processed by recording the initial and final lengths of the potato strips, calculating the percentage change in length, and then taking an average of these changes to plot on a graph against salt concentration.

What does the graph in the experiment represent?

The graph represents the average change in length of the potato strips against the salt concentration, showing the relationship between water potential and osmotic movement.

At what salt concentration does the solution become isotonic to the potato strips?

The solution becomes isotonic to the potato strips at a concentration of approximately 1.4 grams per 100 milliliters, where there is no net movement of water.