INTERNET DIFFUSION ACTIVITY
NAME__________________________
DIRECTIONS: Go to this site: https://authoring.concord.org/activities/12/5a0b08c5-9f10-4e25ba48-c13da07237a7?show_index=true and hit start activity.
Follow the directions on the simulation halfway down the page.
Answer the following question:
1. Which statement best describes the motion of the dye molecules in the water?
The dye molecules:
a. Move in a directed way from high to low concentration
b. Move randomly through collisions in no particular direction
c. Stay close to other dye molecules as they move through the water.
Go to the top of the page and go to page 2
Test the following temperatures and write down the times that it takes for the experiment to run
in the window in the middle of the page:
Temperature
Time to run the experiment
Cold
Medium
High
2. At which temperature did the blue molecules diffuse the fastest?
a. Low
b. Medium
c. High
3. Cells obtain nutrients and get rid of wastes through diffusion. Why do cold blooded
animals, such as snakes and turtles, need to bask in sunshine before they can move was
quickly as warm-blooded animals on a cold day?
Go onto page 3. Conduct the experiment in the middle of the page and fill in the chart below:
Molecule Mass
Temperature
Low
Low
Low
Medium
Medium
Medium
High
High
High
Low
Medium
High
Low
Medium
High
Low
Medium
High
Time
4. Which molecules diffused at the fastest rate?
a. Lightest molecules
b. Heavier molecules
c. Heaviest molecules
5. Methyl mercaptan is a foul-smelling gas that is added to natural gas pipelines. Methyl
acetate contributes to the smell and flavor of peppermint. Methyl mercaptan has a molar
mass of 48 g/mol. Methyl acetate has a molar mass of 198 g/mol. If both substances
were released at the same time, which one would you smell first? Why?
Go to Page 4.
You will run this simulation 3 times. The first time you will try a small pore size. Do not put it
all the way to the left as this will allow no pore size. The second will be in the middle and the
third will be all the way to the right. Record the time it takes for the trace molecule to make it to
the other side. (Don’t forget to click on where it states trace molecule) Also don’t forget to reset
the time before going onto the next size pore.
Pore Size
Small
Medium
Large
Time to cross the membrane
6.
In the initial setup, which molecules are able to cross the membrane?
a. Blue molecules
b. Green molecules
c. Blue molecules and green molecules
d. None of the molecules
7. How does the barrier affect the diffusion of the molecules across the container?
8. How can a membrane be permeable to one substance while being impermeable to another
substance?
Go to Page 5. Read the page and then explore in the simulation. Answer the following
questions:
9. Waste materials excreted by cells are small molecules. The digestive system breaks
down complex molecules into smaller molecules. Why does this make sense?
10. A system has reached equilibrium when the concentration across the barrier is equal on
all sides. Why is it important that living organisms not reach equilibrium in the
concentrations of oxygen and carbon dioxide?