Vernier Software and Technology
Vernier Software & Technology

Diffusion

Figure from experiment 2 from Investigating Biology through Inquiry

Introduction

Diffusion is a process that allows ions or molecules to move from where they are more concentrated to where they are less concentrated. This process accounts for the movement of many small molecules across a cell membrane. Diffusion is one of the processes by which cells acquire food and exchange waste products. Oxygen, for instance, might diffuse in pond water for use by fish and other aquatic animals. When animals use oxygen, more oxygen will diffuse to replace it from the neighboring environment. Waste products released by aquatic animals are diluted by diffusion and dispersed throughout a pond.

One way to measure the rate of diffusion of ions is to monitor their concentration in solution over a period of time. Since ions are electrically charged, aqueous solutions containing ions will conduct electricity. A Conductivity Probe is capable of monitoring ions in solution. This probe however, will not measure the amount of electrically neutral molecules dissolved in water. Salts, such as sodium chloride, produce ions when they dissolve in water. An equation for the dissociation of sodium chloride in water can be written as follows:

\text{NaCl(s)} \longrightarrow \text{Na}^{+}\text{(aq)} + \text{Cl}^{-}\text{(aq)}

If you place a salt solution in a container such as dialysis tubing, the salt can travel through the very small holes in the tubing. When dialysis tubing containing a solution of salt ions is placed into a beaker of water, the ions can diffuse out of the tubing and into the surrounding water. In this way, you will be able to measure the diffusion of salts in a solution of water and determine how concentration gradients and the presence of other particles affect the diffusion of the salt across a membrane.

Objectives

After completing the Preliminary Activity, you will first use reference sources to find out more about diffusion and diffusion through a membrane before you choose and investigate a researchable question dealing with diffusion rate. Some topics to consider in your reference search are:

  • diffusion
  • facilitated diffusion
  • concentration gradient
  • salts
  • ion channels
  • ions
  • dialysis
  • semipermeable membrane
  • active transport

Sensors and Equipment

This investigation features the following Vernier sensors and equipment.

Option 1

Option 2

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

Investigating Biology through Inquiry

See other experiments from the lab book.

1Buffer Investigations
2Diffusion
3Investigating Osmosis
4Chemistry of Membranes
5Investigating Protein
6ATesting Catalase Activity (O2 Gas Sensor)
6BTesting Catalase Activity (Gas Pressure)
6CTesting Enzyme Activity (Spectrometer)
7Introduction to Biofuels: Enzyme Action
8Analysis of Enzymes using Tyrosinase
9Cellular Respiration
10ASugar Metabolism with Yeast (Carbon Dioxide Gas)
10BSugar Metabolism with Yeast (Ethanol)
11Fermentation with Yeast
12Photosynthesis by Chloroplasts
13Transpiration of Plants
14Plant Pigments
15Heart Rate
16Investigating Dissolved Oxygen
17Investigating Primary Productivity
18Modeling Population Dynamics
19Water Monitoring
20Evolution of Cellobiase in Fungi
21Introduction to Molecular Evolution
22Evolution of Yeast

Investigation 2 from Investigating Biology through Inquiry Lab Book

<i>Investigating Biology through Inquiry</i> book cover

Included in the Lab Book

Vernier lab books include word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.

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