Osmosis Over Time
description
Transcript of Osmosis Over Time
By Eliza Normen, Megan Dunlop and Emily McleanAP Biology Period 6
Purpose
To study how time effects rate of osmosis
Hypothesis
If the weight of the potato increases over time and the potato is going through the process of osmosis, than time effects rate of osmosis
Procedure
First make a solution of sugar and water This solution will be 5% sugar Table sugar is a disaccharide of glucose
and fructose Its chemical formula is C12H22O11 Add 5 grams of sugar to a graduated
cylinder. Add distilled water until you reach 100
mL of solution. Poor 25 mL of solution into 4 cups
Procedure (cont.)
Cut 4 potato wedges of relatively equal size Weigh the potato pieces Add each potato piece to 25 mL of the
sugar solution Label the cups of solution 1, 2, 3 and 4 Allow potato 1 to remain in the solution for
10 minutes, potato 2 for 20 minutes, potato 3 for 30 minutes and potato 4 for 40 minutes
Dry off outside of potato piece, weigh and record results
Potato
Experiment
Controls Variables
Amount of time potato was in solution
Molarity of the solution
Potato Type/Potato size
Type of sugar used to make solution
Change in weight due to time spent in solution
Experiment
Test Tube
Observations
Solution was clear and colorless Potatoes were light tan in color After osmosis, potatoes 3 and 4
looked slightly larger than before, as if they had swelled
When potatoes were removed from solution, extra solution remained on the outside
Data
Potato Number
Original Weight of Potato (g)
Weight After Osmosis (g)
Change in Weight (g)
1 5.7 5.8 .1
2 5.4 5.5 .1
3 5.3 5.45 .15
4 5.8 6.0 .2
Change in Mass
Potato Number
Original Weight (g)
Change in Weight (g)
Percent change in Weight
1 5.7 .1 1.75%
2 5.4 .1 1.85%
3 5.3 .15 2.83%
4 5.8 .2 3.45%
Graph
ConclusionDoes Time effect Osmosis?
Time does effect osmosis The longer the potato was in the
glucose solution, the more the water went into the potato
The water went from high to low concentration through the process of osmosis to attempt to reach equilibrium
Restate Purpose
The purpose of this experiment was to see if time effects osmosis
From our experiment, we can conclude that the answer is yes
Hypothesis was Correct!
Our hypothesis predicted that time would effect osmosis
If the weight of the potato increased after a certain amount of time in the solution, than time does effect osmosis
Experimental Errors
Human error: The potatoes may not all have been in exactly the same amount of solution
All remaining solution might not have been dried off from outside of potato
Equipment error: The balance beam may not have accurately recorded the weights of the potato
What would we do differently? Make all the potato pieces the exact same
weight and size Try a different solution, such as salt
dissolved in distilled water Keep potato pieces in solution longer before
measuring change in weight Try a different fruit or vegetable, like an
apple Test to see if there a point at which the
potato reaches equilibrium and time no loner effects osmisis
Osmosis
Osmosis is the diffusion of water across a membrane
Water naturally moves from areas with high concentration of water to low concentration
It moves from areas with a low concentration of solute to a high concentration
This process does not use energy
Osmosis Across a Membrane
What we learned
A semi-permeable membrane allows some substances to move into and out of the cell, while it blocks other substances from moving across the cell
The flow of water is regulated by aquaporins (proteins located in the cell membrane)
Time effects osmosis. The longer the potato was in the solution, the more water diffused into it
Aquaporin
Side View
Sources for Pictures
http://www.aquapuredrinkingwater.com/reversepic.jpg
http://images.asia.ru/img/alibaba/photo/50353563/Potato.jpg
http://www.made-in-china.com/image/2f0j00EMptukCsgHqvM/Test-Tube-10ml-7ml-5-5ml-G1001-G1002-G1003-.jpg
http://img.tfd.com/wiki/a/a5/Aquaporin-Sideview.png