This virtual lab has four sections:
Sections 1 and 2 discuss the principles of diffusion. First, you will be using a simulation that discusses some principles of diffusion. Next, you will watch a demonstration of a diffusion lab using starch and iodine that tests these principles.
Sections 3 and 4 discuss the principles of osmosis. Like the first two sections, you will first use a simulation that discusses osmosis followed by a demonstration of an osmosis lab that tests these principles.
During each simulation, you will have to read very short pieces of text as well as observe short simulations in order to answer sets of questions.
For the lab demonstrations, all questions are answered from the observations and data of each demonstration, based on what you should learn about the principles of diffusion and osmosis.
Net diffusion (diffusion) is the movement of particles
At the very beginning of the simulation, which side had the greatest concentration of blue particles?
The type of energy that diffusion uses to move particles is
Diffusion moves particles from areas of
Eventually side A and side B will come to equilibrium, which is when the concentration is
When the temperature is higher, the movement of the molecules is
When this lab is set-up:
where is the concentration of iodine the highest?
where is the concentration of starch the highest?
What color indicates when starch interacts with iodine?
At the conclusion of the diffusion lab (in the video, above):
Was the color of the fluid in the beaker changed:
Was the color of the fluid in the dialysis tube changed:
Where did you see evidence that starch and iodine interacted (in the dialysis tube or in the beaker):
Which chemical (starch or iodine) was able to cross through the plastic of the dialysis tube?
Why did this chemical cross through the plastic bag?
Which chemical was not able to cross through the plastic of the dialysis tube?
Osmosis is the movement of
What is the solvent?
Does osmosis apply in a situation in which there are no particles dissolved in water?
In the simulation, to which side did the water move to?
Why is this so?
It is best for living cells to be in what type of solution?
Consider why this may be so - this type of solution helps the cell to maintain their
Living cells that are placed in hypertonic solutions will lose
This is because water will always osmose toward the
If a cell is placed in a hypotonic solution, it will
If this continues to happen, the cell will eventually
Consider that the concentration of salt in normal blood cells is 0.9%. If you were sick and in the hospital, especially with something like the flu, you might become dehydrated and would need to receive an IV of saline solution to return your body's fluid levels to homeostasis. What is the concentration of the IV saline (salt) solution given to you by the hospital?
Imagine someone who has become ship-wrecked on an island in the middle of the Pacific Ocean without immediate access to freshwater. The island is surrounded by water that has a salt concentration of approximately 3.5%. If the typical concentration of salt in human cells is approximately 0.9%, explain, from the concept of osmosis, why drinking seawater is a bad idea.
Question - what evidence would model the action of osmosis in a lab setting?
This demonstration tests the principles of osmosis by comparing three different solutions:
distilled water (pure water that has nothing dissolved in it) versus the solution inside of a set of deco cubes (gelatinous cubes)
sucrose solution (sucrose + water) versus the solution inside of a set of deco cubes (gelatinous cubes)
Remember, osmosis is concerned with the movement of water across a semipermeable membrane. Also recall that in osmosis, water will tend to move toward the hypertonic solution.
In this demonstration, the presenter will place three deco cubes in a DI water solution and three deco cubes in a sucrose solution. Both sets of deco cubes will be permitted to soak for the same length of time - 120 minutes - the mass will be taken prior to soaking, after 20 minutes of soak time, after 40 minutes of soak time, and after 120 minutes of soak time.
Observe For This:
Changes in mass (she improperly refers to this as "weight").
If the deco cubes gained mass at the end of the demonstration, they likely gained water
If the deco cubes lost mass at the end of the demonstration, they likely lost water
If the mass of the deco cubes is unchanged, they neither gained nor lost water.
Question to consider when interpreting the data from this section: What would a change or non-change of the mass of each set of deco cubes during and after the demonstration tell you about the types of solution in each set-up?
Three Basic Types of Solutions:
Hypertonic - solution with the highest solute concentration.
Hypotonic - solution with the lowest solute concentration.
Isotonic - when both solutions have equal solute concentrations.
I promise that I read the above section, titled, "Read this before you move forward."
During the set-up of the lab:
What was the initial mass of the 3 deco cubes that were placed in the DI (distilled) water?
What was the initial mass of the 3 deco cubes that were placed in the sucrose solution?
After 20 minutes of "soak time" in each solution:
What was the mass of the 3 deco cubes that were placed in the DI (distilled) water?
What was the mass of the 3 deco cubes that were placed in the sucrose solution?
After 40 minutes of "soak time" in each solution:
What was the mass of the 3 deco cubes that were placed in the DI (distilled) water?
What was the mass of the 3 deco cubes that were placed in the sucrose solution?
After 120 minutes of "soak time" in each solution:
What was the mass of the 3 deco cubes that were placed in the DI (distilled) water?
What was the mass of the 3 deco cubes that were placed in the sucrose solution?
What was the initial mass of (from #20):
Deco cubes that were placed in the DI (distilled) water?
Deco cubes that were placed in the sucrose solution?
What was the final mass (after 120 minutes) of (from #23):
Deco cubes that were placed in the DI (distilled) water?
Deco cubes that were placed in the sucrose solution?
What was the change of mass of (final mass - initial mass = change of mass):
(If it lost mass, record this as a negative number: -1.1)
Deco cubes that were placed in the DI (distilled) water?
Deco cubes that were placed in the sucrose solution?
In the trial in which the deco cubes were placed in the DI water (for the first two blanks, the answer is either - deco cubes or the DI water):
where was the hypertonic solution?
where was the hypotonic solution?
How do you know?
In the trial in which the deco cubes were placed in the sucrose solution (for the first two blanks, the answer is either - deco cubes or the sucrose solution):
where was the hypertonic solution?
where was the hypotonic solution?
How do you know?
In which solution did the deco cubes gain the most mass (DI water or sucrose solution)?
Which solution would have been the most like a hypotonic solution for each of these trials (DI water or sucrose solution)?
How do you know (be brief)?
Which solution was the most like a hypertonic for each of these trials (DI water or sucrose solution)?
How do you know (be brief)?