Download Diffusion

C1 Exercise
Diffusion & Osmosis
1.
Molecules are always moving. In gases and liquids they move randomly. The molecules collide
with each other and spread out. This happens by diffusion.
a.
Tom was watching television when his mother sprayed some air freshener at the other side of
the room. After a few minutes Tom could smell the scent of the air freshener. Fill in the blanks
in the following flow charts to explain what happened.
The air freshener
molecules were at
a _____________
concentration near
the can after they
had been sprayed.
b.
The _________
______________
______________
moved about
randomly. They
collided with
each other and
other molecules
in the air.
The air freshener
molecules moved
from their regions
of ___________
concentration
near the can to
regions of
____________
concentration.
Tom then made himself a drink. He added some
blackcurrant concentrate to water in a glass. After a
few minutes, all the solution was in the same purple
colour.
Explain what happened in the flow chart below.
c. Write down three chemicals which move in or out of cells by diffusion.
___________________ ___________________ ___________________
Some __________
_______________
_______________
reached Tom’s
nose, so he could
smell the scent
C1 Exercise
2.
Osmosis is a special case of diffusion.
a.
Write down a definition of osmosis.
_____________________________________________________________________________
_____________________________________________________________________________
b.
The diagram shows a semi-permeable bag filled with glucose solution. It is put in a beaker of a
glucose solution with a different concentration. Draw arrow(s) to show the movement of water
molecules between the two solutions.
c.
Animal cells can be damaged if their water balance is upset. Explain what happened to the cells
under the following situations.
(i) A red blood cell was put in a very dilute glucose solution.
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(ii) Another red blood cell was put into a concentrated sugar solution.
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
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C1 Exercise
Suggested Answer
1.
a.
high
air freshener molecules
high
lower
air freshener molecules
b.
The blackcurrant juice molecules were at a high concentration near the area after they had
been added.
The blackcurrant juice molecules moved about randomly. They collided with each other
and other molecules in the solution.
The blackcurrant juice molecules moved from their high concentration regions to regions
of lower concentration.
At last, the blackcurrant juice molecules spread evenly in the solution, so the blackcurrant
juice solution was in the same purple colour.
2.
c.
Any 2: oxygen, carbon dioxide, glucose, amino acids, urea or any other acceptable
answers.
a.
Osmosis is the net movement of water molecules from a region of higher water potential
(or dilute solution) to a region of lower water potential (or a more concentrated solution)
across a selectively permeable membrane.
b.
Water molecules will move in both directions, but more will move from right (dilute
solution) to left (a more concentrated solution).
c
(i)
The water potential in the solution was higher than that in the cell.
Water entered the cell by osmosis continuously, so the cell swelled up and burst.
(ii) The water potential in the solution was lower than that in the cell.
Water left the cell by osmosis, so the cell shrunk.