Osmosis in Potato Strips - Bio Lab
Summary
TLDRThis 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
💧 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.
Mindmap
Keywords
💡Osmosis
💡Diffusion
💡Water Potential
💡Semi-Permeable Membrane
💡Potato Strips
💡Solutions
💡Concentration
💡Hypotonic
💡Hypertonic
💡Isotonic
💡Percentage Change
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
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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
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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
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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
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