Diffusion & Osmosis Outline
Edited 11.21.07
[BOLD terms are required; terms in
italics are supplemental (not required)]
A Diffusion Definition:
Click here for ...
A Diffusion Definition
1 [Possible use of video disk
HRW 1A 20823-21828]
Click here for an animation:
http://biologycorner.com/resources/diffusion-animated.gif
Here are
some animated links that may not open directly from this web page. Try
first, then ...
Please
copy and paste
the following
4 web addresses (URLs) one at a time into the Internet
Explorer.
e Then press the
return to see the video. You may then be also asked to
press a play
button to view the video. You may be able to control the scroll bar to replay it.
1. Below is two species diffusion (red/blue
dots).
The two species are the two sizes of molecules
separated
by a membrane barrier. You may also hear
symphonic music being played.
Next
video link
2. This is a silent video on
passive transport (diffusion) (if it plays!)
Second Video Link (Missing in Action as of 11.07; sorry!)
3. The video below is narrated. Please complete the
following quote from this narration. :)
"All molecules are in constant _________ unless at
absolute zero. (Real cold!) The motion is
_________ with molecules moving in straight liens
until they encounter other molecules. The net
result of this process is ________ -- the
movement of a substance where it is in _______
concentration to an area where it is in ______
concentration.
http://www.bio.georgiasouthern.edu/bio-home/nayduch/supplements_files/chapter7/diffusion.mov
(This one may take up to one minute
to silently load, so don't give up too quickly!)
4. Note what happens to the same blue and red dots (molecules) only
after the barrier is gone.
http://ull.chemistry.uakron.edu/genobc/animations/diffusion.mov
From the above animations /videos, diffusion is the
flow of substances (often molecules as
shown as dots) from a
region of H _ G _ _ _ (or G _ _ _ T _ R)
concentration to a
region
of _ _ W _ _
(or L _ _ S _ _ ) concentration
Click here for Diffusion DefinItion ANSWERS
A2. Examples of Gas Phase Diffusion
Diffusion to differing degrees occurs in different states of matter.
a Gas Phase Diffusion:
and then click on
http://www.indiana.edu/~phys215/lecture/lecnotes/lecgraphics/diffusion2.gif
Diffusion of pleasant odors such as P _ _
_ U _ _, & B _ K I _ G;
http://video.google.com/videoplay?docid=5336575425429921218&q=diffusion+%2Bpetri&total=2&start=0&num=10&so=0&type=search&plindex=0
OR
Diffusion of unpleasant odors such as
S _ _ _ K S, G _ _ _ A _ E, and
B _ _ B _ _ _ _ H
b Liquid Phase
Diffusion: (In biology, the liquid is water in living cells.)
Examples of liquid phase diffusion such as
...
1) a D _ _ dissolving in
_ A _ _ _
2) leaf pigments (_ _ A) dissolving in W _ _ _ _
3) deluxe C _ _ _ E _ with _ R _ _ _
4)
diffusion in living cells through protein channels occurs across the
C _ _ _ M
_ _ _ R _ N E _
In these four examples, D _ _
_ U _ _ O _ will take place based on the H _ _ T
content. Stirring will speed up the movement of molecules and will
appear to mix the
solutions even faster.
c
Solid Phase Diffusion. There is none due to lack of
M _ _ _ C _ _ _ R M _ T _ _ _
3
The faster molecules move, the _________ the rate of diffusion
Bio R, skip now to the next box (B Osmosis).
Bio H continue on this
box.
Some factors which affect the rate of diffusing molecules are:
a. The T _ _ _ E _ _ T
_ _ _ of the system
b. The difference in C _ _ _ E _ _ R _ _ I _ _ of
molecules across a barrier
c. The S _ _ _ of the molecules as
compared to the openings (pores) in the barrier
d. The S _ _ P _ and orientation of the
molecules as the approach the barrier
Click here for the
ANSWERS to this section.
B Osmosis:
See the following three video clips:
Here are some
more animated or video links. Please
copy and paste (link to
instructions)
the following 3 web addresses (URLs) one at a time
into the Internet Explorer window.
The first link showed diffusion/osmosis in a living
protozoan. It was no longer available from Yahoo on 11.07.
The second link below showed osmosis initially in red blood cells. It
included the definition of osmosis. It too
was missing in action, again according to Yahoo, on 11.12.07, when I checked
this activity.
The third link below showed osmosis of water into sucrose across a
semi-permeable membrane. Didn't Yahoo sell off its video collection to
somebody? Again, it is not there since last year.
Based not on the missing summary of all three of
these videos, but rather on prior knowledge,
answer the following:
1
Definition of osmosis -- The diffusion of _ A _ _ _ molecules
from a region of
________ concentration to a region of ________ concentration.
2
Practical examples
of water diffusion:
a. 
Dirty pots should be soaked in (hot/cold) ______ water
because at that temperature the rate of M _ _ _ _ _ _ _ R
M _ _ I _ N
is much
faster
b
Clothes on a line dry faster on a (hot/cold) ______
(high/low) ________ humidity day
c Clothes on a line dry slower on a ______
(temp) ______ (humidity) day
d Other examples:
__________________________________________
Click here for the ANSWERS to this section!
C.
Diffusion rates
in two Petri dishes (video)
The following video clip can
not be played directly from this web site. Please copy and
paste this web address (URL) into Internet Explorer (e)
and play it from there. An
alternate method to play this video is to right click the video and choose
Save to Target
and then save it in your student F drive. From this F drive you can then
play it.
Advance the bottom scroll bar (if possible) until 0:45 seconds in and play through at least
1:45. That way you
avoid all the slow heating and grinning. Kalt (German) is
cold and heiss ( translated spelling) is hot. Be alert, the scientist makes three
technical
errors in the scientific method
as he first heats a fluid and them pours fluids into twin Petri Dishes and
finally adds a dye known as potassium permanganate.
(I really hope this one is still available; it was very
good!)
http://video.yahoo.com/video/play?p=diffusion+-music+-rock&toggle=1&cop=&ei=UTF-8&b=4&oid=cd22586105db12aa&rurl=lbs.bw.schule.de&vdone=http%3A%2F%2Fvideo.yahoo.com%2Fsearch%2Fvideo%3Fp%3Ddiffusion%2B-music%2B-rock%26toggle%3D1%26cop%3D%26ei%3DUTF-8
Unfortunately, this video too has gone the way of the
Dodo. I did a search & failed.
What are the three errors in the scientific method that are shown?
(1) When heating the liquid, he fails to
__________________________________
(2) When placing the twin Petri Dishes, he places the Kalt
(cold) dish
_________________________________________________
(3) When adding the dye pellets, he does not
____________________________
a In this demonstration, the independent
variable is ________________________
b In this demonstration, the dependent variable is ________________________
c To which Petri dish was heat
added? ___________
d
In which Petri dish did the molecules move faster? ___________
e
In which Petri dish did molecules diffuse faster? ___________
f
A general relationship is that the ________ the heat, the ________ molecules
move, the _________ the rate of diffusion.
Click here for the ANSWERS to this section!
D. Barriers to Diffusion
1
Natural cell barriers such as the C _ A _ N _ _
_ R O _ _ _ _ S within the
lipid bilayer (2 layers of lipids) in the CELL
MEMBRANE (_ L _ _ M _)
MEMBRANE control the flow
of molecules in and out of cells
phospho-lipid bilayer with unequal protein channels (green) within
distributrion of particles
a lipid bilayer of a cell membrane
a.
(Italics = Bio H only)
A barrier which has the ability to choose (select or differentiate)
which molecules can cross it is known as a semi ( S _ _ _ C _
_ V _ _ _ or _ _ F _ E R _ _ T _ _ L _ _) permeable
membrane.
2
Membrane permeability (in decreasing order of priority) is regulated by
environmental. factors such as:
a _ _ Z _ of the molecule
(The rest of this blue box is italics = Bio H)
Water Molecule
Channel (turquoise) in cell membrane
b. Whether or not the molecule is P _ _ _ R
(charged) (See water above)
Is water polar or non-polar?
_____ Explain!
_____________________________________________________________
c Molecular S _ _ P _ & O _ _ _ N T _ _
I _ N as it approaches _ R _ _ E _ _
channels (See turquoise channel above)
Click
here for ANSWERS to this section!
E
Types of Diagram Set-ups in diffusion
problems
(All
students resume at this point!)
You will shortly learn
how to do diffusion problems. There are only two major formats to
the way diagrams must be
set up. Then you label concentrations on the diagrams.
1
A tank if partitioned by a _ _ _ _ (differentially or
selectively) permeable membrane
(Alternatively [TR #6] ) Different molecules (shown by different
colored dots), often
at differing concentrations, are then placed on the two sides of the membrane.
In the two sets of diagrams above, the containers (boxes or beakers) appear to
have covers. This is not necessary. At times, the contains may
have open tops.
2
A pouch made from _ _ _ _ (Bio H -- a _ _ F _ E _ E N _ _ _ L _ Y) permeable membrane is
placed in a container filled with a stated fluid. This pouch material is
a
special plastic that has tiny holes in it. You can't see the holes, but
some molecules
are _ _ _ _ _ in size and can fit through the holes.
DIAGRAM OF POUCH
ACTUAL FILLED POUCH
Click here for answers to
this section!
F How to do
diffusion problems (Rules)
1 FACTS TO
REMEMBER IN SOLVING THESE PROBLEMS
Some common molecules found in diffusion problems are ...
Glucose
Lactose (same size as table sugar (sucrose))
Salt (Na Cl) in solid crystal form Water molecule
Did you know??? It is both the number of atoms in the molecule and the
distances
between atoms
in a molecule that determine the size of the molecule.
a Smaller molecules diffuse faster than larger ones. Due
to its small size, which of
the above four molecules diffuses first? ____________
b
Molecules diffuse from regions of _________ conc. to ones of ________ conc.
2 STEPS IN DIAGRAMMING THE PROBLEM
a
Draw & label all stated information on a set-up diagram
(one of the two
formats
in section E above; a partitioned tank or a pouch, but we will use the pouch)
This
drawing will soon become clear when we do specific problems in the next
section!)
b
Change known solute concentrations into equivalent
solvent (water)
concentrations
(If you have 3% sugar (the solute) dissolved in water (the solvent), then the
solvent
concentration is (100%-3%) ______ % water.
c
Draw a thick arrow showing the direction of water diffusion (osmosis)
Why
does the water & not the solute move first and faster than the solvent?
____________________________________________________________
d
Locate where in the diagram water is first gained and place a “G” in
this location.
This location is based on the flow of fluid (water) as
shown by the prior arrow.
e
Draw a thin arrow showing the direction of diffusion of the solute
(sugar or salt)
The solute (sugar or salt) is also
diffusing in the direction O _ _ _ _ _ _ E to that
of the water solvent. The solute is moving at a _ _ _ _ rate compared to the water,
(Bio H only)
After a very long time, the water diffusion
will R _ V _ _ S _
D _ _ E C _ I _ _ and the water will eventually be E _ _ _ L in
concentration
on both sides of the membrane.
Click here to see the answers to this
section.
G & H
(Sample Typical Diffusion Problems)
Do Example 1 (Item G) and Example 2 (Item H)
below in print format in class (if time permits) or for homework (if you ran out
of time.). Use the rules you just learned in F above
to do the following problems.
Only the answers to Ex. 1
(G) are included for reference.
G Example #1 -- A
differentially permeable membrane pouch containing
distilled water (What is the
water % in distilled water?) was placed in a beaker of 5% sugar
solution.
1 Draw & label
all stated information directly on the diagram
Beaker
Pouch
2
Next change the
solute concentration into water conc.
3 Draw a
thick arrow showing water diffusion
4 Place a “G”
where water & mass are first gained.
Click here for the answers to
Section G (Example 1)
H Example #2 -- A
selectively permeable membrane pouch containing a 2%
salt solution was
placed in a beaker of 1% tea.
This time, you must draw you own lovely diagram below.
1 Draw & label
all stated information on a diagram
2 Change the
solute concentration into water conc.
3 Draw a
thick arrow showing water diffusion
4 Place a “G”
where water is first gained
Example 2 (H)
may be done totally in print format.
Click here for the ANSWERS to this
section.
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