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.

Outlines

00:00

💧 Osmosis and Water Potential

This paragraph explains osmosis, a type of diffusion specific to water and solvents. It contrasts a liter of pure water with a liter of seawater, highlighting that seawater contains less water due to the presence of salt. The concept of water potential is introduced, with the example of plant roots absorbing water due to the higher water potential in rainwater compared to inside the roots. The paragraph also describes a laboratory experiment using potatoes to demonstrate osmosis. The experiment involves preparing potato strips, creating solutions of varying salt concentrations, and observing the changes in the potato strips' lengths after they are immersed in these solutions for 20 minutes.

Keywords

💡Osmosis

Osmosis is a biological process that describes the movement of solvent molecules, such as water, across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration. In the context of the video, osmosis is used to explain how plant roots absorb water. The script mentions that rainwater, with a higher water potential than inside the roots, moves into the roots by osmosis.

💡Diffusion

Diffusion is the passive movement of particles from an area of higher concentration to an area of lower concentration, which eventually leads to a uniform distribution of those particles. Osmosis is a special type of diffusion that specifically involves water or other solvents. The video script uses the concept of diffusion to set the stage for explaining osmosis.

💡Water Potential

Water potential is a measure of the potential energy of water in a solution or in a plant, which is influenced by factors such as solute concentration, pressure, and gravity. The video script explains that water moves from an area of higher water potential to an area of lower water potential, as seen when comparing pure water to seawater.

💡Semi-Permeable Membrane

A semi-permeable membrane is a barrier that allows certain molecules or ions to pass through while blocking others. In the video, the concept is used to describe how a cell membrane can separate different water samples, leading to osmosis. The script mentions using a potato as a model for a semi-permeable membrane in the lab experiment.

💡Potato Strips

In the script, potato strips are used as a practical example of a semi-permeable membrane to demonstrate osmosis in a lab setting. The strips act as a model for plant cells, and their change in length after being immersed in different salt solutions illustrates the effect of osmosis.

💡Solutions

The term 'solutions' in the script refers to mixtures of salt and water with varying concentrations. These solutions are used in the experiment to simulate different water potentials and observe how they affect the potato strips through osmosis.

💡Concentration

Concentration, as used in the script, refers to the amount of a substance, such as salt, dissolved in a solvent, typically measured in grams per 100 milliliters. The experiment involves creating solutions with varying salt concentrations to study their effect on the osmosis process.

💡Hypotonic

A hypotonic solution is one with a lower solute concentration than another solution. In the video, hypotonic solutions cause water to enter the potato strips by osmosis, leading to an increase in length, indicating a higher water potential inside the solution compared to the potato.

💡Hypertonic

Hypertonic solutions have a higher solute concentration than another solution. The script describes how hypertonic solutions cause water to leave the potato strips by osmosis, resulting in a decrease in length, indicating a higher water potential inside the potato.

💡Isotonic

An isotonic solution has the same solute concentration as another solution, resulting in no net movement of water across a semi-permeable membrane. The video script notes that at a certain salt concentration (1.4 grams per 100 milliliters), the solution is isotonic to the potato, meaning there is no net movement of water.

💡Percentage Change

Percentage change is used in the script to quantify the change in length of the potato strips after being exposed to different solutions. It is calculated to determine the effect of osmosis and is crucial for analyzing the experimental data.

Highlights

Osmosis is a type of diffusion that affects water and other solvents.

Seawater has a lower water potential due to the presence of salt.

A partially permeable membrane can cause water to move from an area of higher water potential to one of lower water potential.

Plant roots absorb water through osmosis due to the higher water potential of rainwater compared to the root interior.

A lab experiment using potatoes can demonstrate osmosis.

Potato strips are prepared to be the same length for consistency in the experiment.

Six solutions with varying salt concentrations are prepared for the experiment.

The potato strips are immersed in the solutions to observe changes over 20 minutes.

The length of the potato strips is measured before and after the experiment to track osmotic changes.

Strips in more concentrated solutions become softer, indicating water loss.

Strips in lower concentrations are more turgid, indicating water intake.

Data is recorded and processed to calculate the percentage change in strip length.

A graph is used to illustrate the average change in length against salt concentration.

At lower salt concentrations, potato strips increase in length due to water intake by osmosis.

At higher salt concentrations, potato strips decrease in length due to water loss by osmosis.

The point where the graph crosses zero indicates an isotonic solution where there is no net movement of water.

The experiment demonstrates the concept of hypotonic and hypertonic solutions in relation to osmosis.

Transcripts

[Music]

osmosis is a special type of diffusion

that applies to water and other solvents

if you take a liter of pure water and

compare it to a liter of seawater which

is very salty there is less water

present in the seawater liter because

some of that leader is occupied by salt

the salt water has a lower water

potential if there is a partially

permeable membrane like a cell membrane

separating two different water samples

there will be a net movement of water

from that place with a higher water

potential to the place with a lower

water potential this is the reason plant

roots take in water the rainwater that

enters the soil has a higher water

potential than inside of the roots so

water moves into the roots by osmosis

where we can demonstrate this in a lab

setting using potatoes first you need a

cork board to get your potato strips

push it through the potato then use the

narrower piece to push the strip out for

this experiment we need 18 strips once

you've got as much as you need tidy them

up with a knife and remove the skins all

of the strip's need to be the same

length to begin with here were cutting

them all down to 6 centimeters once

they're ready get 6 Biggers and put

three tubes in each this will give you 3

repeats for each solution the next thing

to do is make your solutions put a sheet

of paper on the balance hit tear to get

the starting point of 0 and other sold

until it reads one gram

[Music]

once that's in the bigger you need 100

milliliters of water or another

measuring cylinder keeping your eyes on

level with 100ml until it reaches the

line and then add that the assault here

we've just made a salt solution of 1

gram per 100 milliliters in this

experiment we need 6 solutions 0 grams

per hundred ml which is just pure water

and 1 to 5 grams per hundred ml in one

gram increments once the solutions are

ready pour them in to immerse the potato

strips start the timer leave them where

they are for 20 minutes

[Music]

[Music]

after 20 minutes you have to measure all

of the strips and measure them as

accurately as possible to the nearest

millimeter is good for this experiment

as you're working through the potato

strips you'll probably notice that the

ones immersed in the more concentrated

solutions are more soft while the ones

immersed in lower concentrations are

more turgid be sure to make a quick note

of each value you measure as you're

going along to process the data you need

a table of results with all

concentrations listed as well as the

starting lengths of the strip's these

all start at 6.0 centimeters in the next

column put in the values you measured

and then calculate the percentage change

for each individual strip notice the

negative sign on some values this tells

us whether the strip's increased or

decreased in length

next you can take an average of changes

in length these are the values that we

need to put on the graph the graph shows

the average change in length against the

salt concentration and the results from

this experiment your nice downward curve

the lower salt concentrations result in

an increase in length of potato strip

meaning water has entered the potato

strips by osmosis this means there is a

higher water potential inside the

solution compared with the potato we

have a hypotonic solution at higher salt

concentrations however we have a

decrease in potato strip length this

tells us the water potential is higher

inside of the potatoes so water has left

the potato strips by osmosis we can say

that the solutions are hypertonic to the

potatoes at the point the graph crosses

0 which is about 1.4 grams per 100

milliliters of salt the solution is

isotonic meaning the water potential

inside the potato is equal to the

solution so at that point there is no

net movement of water

[Music]