The Rate of OSMOSIS
What will affect the rate of osmosis ?
1) Concentration gradient?
2) Surface area?
• 1.The rate of osmosis is affected by the
concentration gradient?
Hypotheses:
1. The rate of osmosis is affected by the
concentration gradient.
2. It increase with the concentration gradient.
Set up:
Step1:Placed potato A,B and C in 3 cups with pure water respectively.
Step2:Presence of pure water in potato A,B and C respectively.
Then dissolve 2 units of sugar into the water inside potato B and 4 units of
sugar into the water inside C.
Step3:Observe the water level after 1 day.
Sample rise of water level (cm)
A
Unchanged
B
0.7
C
0.9
The concentration gradient of C is greater than that of B.
Larger amount of water net move into the solution inside potato C than
that of B.
1) Osmosis rate is affected by the concentration gradient. If no
concentration difference, osmosis will not occur, no net water
movement between the solution inside the potato and the water
surrounded the potato by osmosis.
2) If there are concentration difference between the solution
inside the potato and the water surrounded the potato,
osmosis is occurred. Water net move from lower concentration
solution to higher concentration. The greater the concentration
gradient, the faster the rate of osmosis.
• 2.The rate of osmosis is affected by the
surface area?
Hypotheses:
1. The rate of osmosis is affected by the surface area.
2. The rate of osmosis increase with the surface.
Set up:
Step1:Placed potato A,P,Q and R in 4 cups with pure water respectively.
＊Surface area of A:80cm^2／P:40cm^2 ／Q:110cm^2／R:150cm^2.
Step2:Presence of pure water in potato A,P,Q and R respectively.
Then dissolve 1 unit of sugar into the water inside the 4 potato.
Step:3 Observe the water level after 1 day.
Sample Surface area (cm^2) rise of water level (cm)
A
80
0.4
P
40
0.25
Q
110
0.6
S
150
0.7
The surface area of R is greater than that of P.
Larger amount of water net move into the solution inside potato R
than that of P.
1.Osmosis rate is affected by the surface area.
It increase with the surface area.
The surface area of R is greater than that of P.
Larger amount of water net move into the solution inside potato R
than that of P.
It show that the larger the surface area, the faster the rate of osmosis.
Thank you!