# Brownian motion

This is a simulation of brownian motion of a particle that collides with a large set of smaller particles which move with uniform motion in different random directions.

Original Author:

Simulación preparada por Francisco Esquembre para el libro

Creación de Simulaciones Interactivas en Java.
Aplicación a la Enseñanza de la Física

(C) Pearson Educación 2004.

Modified by Fu-Kwun Hwang

http://www.phy.ntnu.edu.tw/ntnujava/

Ejs Open Source Brownian Motion Gas Model Java Applet

### Translations

Code Language Translator Run

### Software Requirements

SoftwareRequirements

 Android iOS Windows MacOS with best with Chrome Chrome Chrome Chrome support full-screen? Yes. Chrome/Opera No. Firefox/ Samsung Internet Not yet Yes Yes cannot work on some mobile browser that don't understand JavaScript such as..... cannot work on Internet Explorer 9 and below

### Credits

Francisco Esquembre; Fu-Kwun Hwang; lookang

### end faq

http://iwant2study.org/lookangejss/03thermalphysics_08kineticmodel/ejss_model_brownianmotionwee/brownianmotionwee_Simulation.xhtml

### end faq

surprisingly similiar random movement between brownian and diffusion.

### Key inquiry question: How can we explain the effects of heat gain or heat loss on matter?

2. Brownian motion

• Brownian motion provides evidence of the movement of molecules. Pollen grains in water and smoke particles in air are observed to be in constant random motion due to collisions by the unseen fastmoving molecules of water and air respectively

### Other Resources

http://mw.concord.org/nextgen/interactives/

### Add a drop of dye anywhere in the container, and watch it diffuse through the water.

Click in the model to add a drop of dye. Watch how the molecules move through the water. Trace an individual molecule to see how it moves through the liquid.

### How does temperature affect the rate of diffusion?

Explore the role of temperature on the rate of diffusion. Set the temperature, then remove the barrier, and measure the amount of time it takes the blue molecules to reach the gas sensor. When the gas sensor has detected three blue molecules, it will stop the experiment. Compare the diffusion rates at low, medium and high temperatures. Trace an individual molecule to see the path it takes.

### How does molecular mass affect the rate of diffusion?

Explore the role of molecular mass on the rate of diffusion. Select the mass of the molecules behind the barrier. Remove the barrier, and measure the amount of time it takes the molecules to reach the gas sensor. When the gas sensor has detected three molecules, it will stop the experiment. Compare the diffusion rates of the lightest, heavier and heaviest molecules. Trace an individual molecule to see the path it takes.

http://lab.concord.org/embeddable.html#interactives/sam/diffusion/3-mass.json

### How does pore size affect the diffusion of different molecules?

Biological membranes are selectively permeable; some molecules can cross while others cannot. One way to affect this is through pore size. Change the pore size with the slider to change the permeability of the membrane to the different types of molecules. Trace an individual molecule to see the path it takes.

### Exchanging gases across a cell membrane

Cell membranes are composed of two layers of phospholipids (a phospholipid bilayer). Some molecules are capable of crossing this membrane directly, without use of specific membrane channels.

Oxygen and carbon dioxide are two molecules that can freely cross the cell membrane. In aerobic cells, oxygen is necessary for cell functioning and carbon dioxide is produced as a waste molecule. Hence, the cell “wants” oxygen to enter and carbon dioxide to leave. But molecules don’t move only in one direction–they diffuse randomly across the membrane.

Set up the model with high oxygen and low carbon dioxide outside the cell and low oxygen and high carbon dioxide inside the cell. In which direction do the oxygen and carbon dioxide molecules move?

### How does pore size affect the diffusion of different molecules?

Biological membranes are selectively permeable; some molecules can cross while others cannot. One way to affect this is through pore size. Change the pore size with the slider to change the permeability of the membranes to the different types of molecules. Trace an individual molecule to see the path it takes.

### Other resources

http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1121.0 simplied flu spreading model by Fu-Kwun Hwang