Diffusion

Introduction

What happens to the rate of diffusion as the concentration of salt is increased? Diffusion is the movement of particles from higher chemical concentration to lower chemical concentration. It is readily observed, for example, when dried food like spaghetti is cooked; water molecules diffuse into the spaghetti strings, making them thicker and more flexible. This lab is solely focused on the concentration of sucrose in a potato in relationship to the rate of diffusion.

Experimental Design

Equipment list:

3 15 cm lengths of dialysis tubing

3 400 mL beakers

1% NaCl solution, 10 mL

5% NaCl solution, 10 mL

10% NaCl solution; 10 mL

1 potato with 4 plugs taken out (approx 3cm each)

0.0M Sucrose, 5-10 mL

.33M Sucrose, 5-10 mL

.67M Sucrose, 5-10 mL

1.0M Sucrose, 5-10 mL

1 microscope slide

1 Coverslip

Scalpel

Forceps

Compound Microscope

LabPro

Computer with Logger Pro installed

Vernier Conductivity Probe

Vernier Gas Pressure Sensor

1 Graduated Cylinder; 10 mL

1 Funnel

1 Craft stick

1 Pipet, 1 mL

1 Thermometer

Plastic wrap

1 Onion

1 Cork Borer

Distilled Water

1 Balance

Paper Towels

1 Wash Bottle with dH2O

1 400 mL beaker for waste liquid

1 Beaker for dH2O

Procedure:

1) Open Lab Pro and set the conductivity probe for 2000 uS/cm

2) Get 3 400 mL beakers filled with 300 mL of dH2O; label 1%,5%, and 10%

3) Dry a piece of dialysis tubing and fill with 10 mL of 1% NaCl solution (repeat with 5% and 10%)

4) Place the tubing in the corresponding beaker and stir slowly for approximately 15 seconds

5) After stirring start your data collection let it run for 2 minutes

6) Use LabPro to calculate the rate of diffusion using the line function

7) Clean the area before proceeding to part 2

Part 2

1) Set up your Gas Pressure Sensor by connect it to channel 1 of the LabPro

2) Open the preset data collection table called “22 osmosis”

3) Cut a piece of string that when tied will still fit around your potato

4) Use a cork borer to make 4 well spaced hole in the potato 3 cm down

5) Save the plugs and mark the holes (0.0, .33, .67, and 1.0

6) Rinse the wells out then blot dry, be careful not to crack the well walls

7) Fill the 0.0 well with 0.0M sucrose and let it sit for 5 min

8) Empty the well and refill with fresh 0.0M sucrose

9) Place the stopper assembly