In this activity, you will plan the design of a model that you will then construct on the computer to investigate the diffusion of odor. You will then use this model to come up with a scientific explanation that answers your research question.

In the previous activity, you began to explore some of the basic properties of particles in a gaseous state. You did this by exploring a phenomenon called diffusion. Today, you'll have the opportunity to choose a mechanism you believe led to the patterns observed in odor diffusion, and study this further using the Virtual Particle Sandbox model.

To guide your explanation of particle motion, you will need to form a focus question that you will investigate. Based on your observations of diffusion and introduction to the mode, try to come up with a single question to explore with the model You will write the question you are interested in investigating on the next screen.

Now that you have been introduced to how odor diffuses throughout a space and brainstormed possible factors that may influence this, you will work to develop a model that represents this phenomenon. To guide your model, you will focus on one specific aspect of odor diffusion. To do this, first, think of a question that you can explore using the Diffusion Sandbox model that you explored yesterday. Then, write it in the box below and answer the following questions. 

Now you can begin to use the model to find an answer to the focus question you developed. This question is presented below for your reference as you interact with the model and answer the questions below. 

Below is the sandbox model you were introduced to yesterday. You can also see your research question from the previous step right below the model. Design your initial experiment and save it.

1. Press SETUP. This gets the model ready for you to interact with it and then run. 
2. Press GO/STOP/ADD ELEMENTS to run the model.
3. Set the MOUSE-INTERACTION chooser to whatever setting you want to use to start building your world. Then use the cursor and mouse button to draw, erase, paint, etc... different elements. Add elements to your world such that you will be able to collect data and draw conclusions that will help you answer your question.
4. Click SAVE MODEL button. This will download a file that you can use in the following steps to reload continue working on your model. Make sure you use a unique and comprehensible name for the downloaded file such as "yourname_movementofodor_model1".

Note: It is very important for you to keep in mind that you are going to keep working on the same model and improving it. So, plan accordingly.

Next, test your model to see how the particles move in it.

1. Click LOAD MODEL button and choose the file you saved in the previous step.
2. Make sure the MOUSE-INTERACTION is chosen as "none - let particles move".
3. Click GO/STOP/ADD ELEMENTS button to start your experiment.
4. Record the observations and notes in the questions below the model. Because some particle interactions involve randomness, it's important that you run your experiment more than one time.
5. When you're ready to repeat the experiment, reload your model back by clicking the LOAD MODEL and selecting the model file you saved in the previous step again. 

When you've collected your data, you may want to average some measurement values that changed over the course of many runs. For example, if you ran the model three times with the same starting conditions, you might want to average the value of your dependent variable (pressure, number of molecules, time, etc) over those runs. Furthermore, you may want to consider the following questions as you refine your model:

• Are there changes to the position of the wall or obstacles that you should make for your research question?
• Are there changes to the temperature of the gasses you should make for your research question?
• Do you need to change the number of particles in the air or in containers?

1. Before testing the changes you made, switch the MOUSE-INTERACTION chooser to "big eraser" or something else that is not "none - let particles move" and click the SAVE MODEL button again and give your model another unique, distinguishable name.
2. Repeat steps 1-5, loading the newest model until it:
   • Provides evidence to help you write a scientific explanation the question you proposed for your experiment at the beginning of this activity.
   • Helps you understand important mechanisms at work that explain or cause some (or all) of the patterns in the data.

You will now prepare a scientific explanation  to answer the question you proposed to focus on at the beginning of the activity.

A scientific explanation has:

• A Claim: A one-sentence claim that answers the question you investigated.
• Evidence: Data used to support the claim.
• Reasoning: Relevant scientific principles, along with logical links to why these principles apply to this data and why the data counts as evidence.

Make an outline of these elements using the questions below.