In this activity, you will discuss odors and why things can be smelled from a distance. You will need to call upon and share your prior knowledge and ideas about particles and molecules that might help account for the observed phenomenon. You will also use a computational model to explore this phenomenon.

Today we begin our unit on the particulate nature of matter, or PNoM for short. Throughout this unit you'll have the opportunity to ask questions about why matter behaves the way it does and you'll be given the tools and freedom to find answers to those questions!

The first activity in this unit is on detecting odors.

“What patterns are there in how odors travel?“

Predict

Your teacher will open two containers at different locations in the room at about the same time, both containing the same substance, but at different temperatures.  The substance is one that will have a recognizable odor. 

Now that you've considered how odors behave in a room, you will get to experience it directly. Your teacher will bring out some odors and allow them to diffuse throughout the room. While this happens, record your observations and thoughts and then answer the questions below. 

After experiencing odor diffusion in a room, you may have a better idea of what affects this process. Answer the questions below to explore this.

Then consider how we can model particle movements during diffusion?

In the next activity you will be working in a team of two people to build a model of the phenomena you observed. Using a "sandbox" model -- which is a model that provides the tools, agents, and behaviors of a system, but allows you to design the system -- you will attempt to replicate the behavior of odors as they move around a room.

The model is introduced below. Here is how you can run the model:

1. Press the SETUP button on the top left to reset the model.

2. Press the GO/STOP/ADD ELEMENTS button the run the model. This button will turn dark blue meaning the model is actively running. 

3. You can pause the model by clicking the GO/STOP/ADD ELEMENTS button again.

Explore the model freely and answer the questions below.

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.

In the previous activity you planned and carried out an experiment concerning the diffusion of gases. To collect data, you used sensors that we provided you. In today's activity you will attempt to quantify the results of your experiment by programming sensors into your sandbox model.

The big question: How can sensors help me analyze patterns of change?

In the previous activity, you wrote a scientific explanation to the topic and focus question that you are examining with your experimentation in the model. Now, work with another classmate to refine your explanation from before, using the criteria below to guide you. 

Claim

• The claim answers the question in one sentence.

Evidence

• Data from the classroom experiment is included.
• Data from the computer model is included.
• What the data means is explained.

Reasoning

• One or more scientific principles are included.
• Why the scientific principles are relevant is explained.
• The entire explanation is coherent; the reasoning is connected to the claim and the evidence.

To strengthen your claim and to understand gas particle behavior further you will be able to add detectors to your computer model. You will be able to design the detectors that you will be using ,as well. What kind of data would be most useful for the detectors to report? Some examples are:

• How long it takes before a particle reaches the detector? 
• What is the average number of particles that have been at the detector since it was first turned on?
• What is the concentration of particles near the detector?
• Are there any particles near the detector?
• Which direction are particles traveling when they pass the detector?
• What is the temperature of the gas (average speed of the particles) at the detector?

Below is the sensors sandbox model you were introduced to yesterday. You can also see your research question from the previous step right below the model.

1. Press SETUP. This gets the model ready for you to interact with it and then run. 
2. Click LOAD MODEL button and load your model from yesterday by choosing the file you saved.
3. Press GO/STOP/ADD ELEMENTS to run the model.
4. Try to add sensors to your model. 

Note: In this step, just focus on making sense of which sensors you have, how do they work, and what you can do with them . Do not try change the sensor code yet.

In this last step, you will modify the code of the sensors to identify patterns in your model.

1. Load your saved world, using one of the LOAD button at the bottom left of the sandbox window.
2. Change the sensor code from the windows CODE 1, CODE 2, CODE 3, and CODE 4 to create the type of sensor behavior(s) you want.
3. Press GO/PAUSE/ADD ELEMENTS to run the model.
4. Set the MOUSE-INTERACTION chooser to add/move sensors. And add sensors or move the ones you have added using your mouse.
5. While you are working you may choose to save your world periodically using the SAVE button so that you do not risk losing your progress .

Note: Do not change the code of the EXAMPLE 1, EXAMPLE 2, EXAMPLE 3, or EXAMPLE 4 windows. These codes are provided to you so that you can copy them and paste them to the code windows in case you want to reset the code of a sensor or try a new code.

Next, test your model to see how the particles move in it by turning the MOUSE-INTERACTION chooser to "none - let particles move"

1. Record the results in the following questions. Because some particle interactions involve randomness, it's important that you run your experiment more than one times.
2. 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, time, etc) over those runs.

Repeat any of these steps until the sensor data either:

• helps you discover interesting patterns in the data.
• provides you additional evidence for your scientific explanation from the previous activity.
• helps you understand important mechanisms at work that explain cause some (or all) of the patterns in the data.

Record the relevant data from the model run that you intend to use in the following step.

If you want to use the world you have set up or changed in this step with more sensors in the next step, save your world for future usage. 

In previous activities, you had a chance to explore the particulate nature of matter. Specifically, you experimented with how gas particles diffuse throughout a room and how that behavior changes with temperature. In this activity, you will continue to experiment with gas particles and work to understand how the movement of these particles relates to pressure.

Purpose: How can objects inflated with air hold up the weight of other objects?

Overview: To investigate this question, you will record observations of a syringe filled with air, you will model the syringe together as a class, and will analyze the results from the model to explain the behavior of the syringe.

Brainstorm around this topic by considering the following questions. Include your response in the question below. 

Question

"Why can I compress or expand a syringe filled with air?"

Predict

You will be given a syringe filled with only air and will cover the open end of it with your finger to close it off. Once the syringe is closed you will try to push down on the plunger. With the syringe still closed you will also try to pull the plunger out.

Answer the questions below based on the observations you just made with the syringe.

Question

"Why does the plunger push back when I push on it?"

Model Rules

Your teacher will demonstrate a new model that represents the syringe. The blue wall will represent the edge of the plunger in the syringe. It is allowed to move back and forth within the piston depending what pushes or pulls on it. It can not move further then the edge of the syringe.

We are now going to start experimenting with a modified version of the virtual syringe model that will allow you to simulate applying upward and/or downward forces by drawing a force graph.  

Watch the short video below that demonstrate how to draw an applied force vs. time graph in the model. Pay close attention to which part of the graph represents a push applied to the plunger, and which part represents a pull applied to the plunger.

Positive forces represent an external pull and negative represent an external push.

Now it is your turn to experiment with the Virtual Syringe Force graph model.

1. As you did in the previous exploration, create a world with an even number of particles both inside and outside of the syringe.
2. Press the "Draw Force vs Time Graph" button near the bottom of the NetLogo screen.
3. Click and drag in the graph part of the view to draw the general shape of the external force graph shown to the right.
4. Using the "SAVE" button, save the state of your model so that you can repeat the experiment if you need to.
5. Press PREPARE FOR EXPERIMENTAL RUN and then press RUN EXPERIMENT buttons to test the effects of the force graph on the model.
6. You will sketch the shape of the Plunger Level graph and the shape of the Net Particle Forces graph in the following steps.

1. Import the world you saved that has the syringe capped and different colored particles on the inside and outside of the syringe by clicking the "load another" button and selecting the file you saved earlier.
2. Press "Reset Axes" and then "Draw Force v Time Graph" to draw the shape of the external force graph shown to the right.
3. Press PREPARE FOR EXPERIMENTAL RUN and then press RUN EXPERIMENT to test the effects of the force graph on the model.
4. You will sketch the shape of Plunger level graph and the shape of the Net Particle Forces in the following steps.

Now that we've completed a number of explorations about how force interacts with pressure, lets revisit the questions asked at the beginning of the activity.

In the last activity, you explored how air particles inside of a syringe act when pushing and pulling on the plunger. In this next activity, you'll explore how those same air particles act inside of a syringe when the temperature of the air is also changed.

Purpose: How does temperature impact the interactions of air particles?

Read the brainstorm topic questions below, then write your response.

GOING TO PLACE A VIDEO HERE THAT SHOWS AN EXPERIMENT IN WHICH A SYRINGE IS CONNECTED TO A FLASK. THE EXPERIMENTER HEATS THE AIR INSIDE THE FLASK BY COVERING IT WITH HIS HANDS AND DEMONSTRATES HOW THE POSITION OF THE PLUNGER.

In a moment your teacher will be demonstrating an interesting phenomenon. Make careful observations and record them in question 1 below. Then answer the following questions. 

Keep thinking about your teacher's demonstration.

We are now going to experiment with another version of the Virtual Syringe model, this time through manipulating a temperature graph instead of a force graph.

1. Set the MOUSE-INTERACTION chooser to anything that isn't "none - let particles move". 
2. Press SETUP, and then GO/STOP/ADD ELEMENTS to run the model.
3. Set the MOUSE-INTERACTION to “draw basic wall” or “draw red removable wall” or “draw blue removable wall”. Then add a wall to the bottom of the syringe so that its end is capped and the inside of the syringe is a closed system.
4. Set MOUSE-INTERACTION to “add green particles”. Add particles to both the outside and inside of the syringe. Set the MOUSE-INTERACTION chooser to "none - let particles move" and let the model run until it has reached equalibrium and looks similar to the picture to the right
5. Set MOUSE-INTERACTION to "choose heat/cool region" and then click a spot inside of the closed syringe chamber. This region should temporarily fill up with a brown color to show it has been selected.
6. Click "Draw Temp vs Time Graph," then click and drag in the graph area of the view to draw a graph that represents how the temperature of the air in the flask changed over time during the teacher's demo.
7. Press PREPARE FOR EXPERIMENTAL RUN and then press RUN EXPERIMENT to test the effects of the temperature graph on the model.
8. Once the experiment has run, use the "SAVE" button  to export your experiment.

Question: How can I generate cyclical motion in a piston?

Design An Experiment

A piston is similar to a syringe. Pistons are used in car, train and many airplanes to convert up and down motion in the piston into circular motion. The very first steam engines used pistons to turn train wheels on trains and paddle wheels on steam boats, and a variety of other machines. Below is an animation of a piston. This piston has two nozzles on the top instead on one (like the syringe) and its plunger stick can rock back and forth, so that it can be attached easily to a wheel.

Use the virtual syringe temperature model to recreate the piston behavior. 

Now that we've completed a number of explorations about how temperature interacts with pressure, and you've built a syringe model that mimics a piston, answer the questions below:

In the last activity you explored how pressure and temperature might impact the gas inside of a closed container. As part of this unit, you also attempted to replicate the behavior of a steam piston in your syringe sandbox model. However, we did not consider the role of water in this model (as steam is heated water). In an earlier activity, you also explored how an odor travels through a room. However, we did not consider that the odor came from peppermint oil, a liquid.

Purpose: How do substances change from one state to another?

Consider the question of how substances change from one state to another.

1. Press SETUP, and then GO/PAUSE/ADD ELEMENTS to run the model.
2. Be sure to set the "gravity-on?" and/or "use-graph-for-gravity" switches to "on."
3. To change the forces on the particles, click the DRAW GRAVITY VS HEIGHT GRAPH button and then draw a new graph by clicking and dragging in the graph side of the view.
4. Experiment with different graphs to see how particles behave. For example, think about whether or not gravity is the same throughout the container.
5. Once you've made a graph you're happy with, use the "SAVE" button to save to your machine so that the rest of your classmates can see it.

While conducting the experiment described in the previous steps, answer the questions below:

In reality, gravity is essentially the same throughout the room or a given container.  For that reason, we should use a constant amount of gravity despite the height of the particles.  Try drawing in a constant value for gravity and observing the particles.

Watch the video below:

Now watch the video again.

1. Press SETUP, and then GO/PAUSE to run the model.
2. You can use the attractive and repulsive force graph on the right side of the model to change the way the particles interact with one another.
3. Set the MOUSE INTERACTION drop down menu to "add green particles" add some more green particles to the view.
4. To change the intermolecular forces between particles, click the DRAW GRAPH button and then draw a new graph by clicking and dragging in the graph side of the view.
5. Experiment with different graphs to see how particles behave.
6. When you've found a graph that you like, save your model with the SAVE button.

1. Press SETUP, and then GO/PAUSE to run the model.
2. Set the "MOUSE-INTERACTION" chooser to anything that isn't "none - let particles move"
3. Set MOUSE INTERACTION to "add green particles." Add green particles throughout the space on the left.
4. Set MOUSE INTERACTION to "add purple particles." Add purple particles to the bottom fourth of the space on the left.
5. Make sure the "gravity-on?" switch is set to "on."
6. To change the intermolecular forces between particles, click the DRAW GRAPH button and then draw a new graph by clicking and dragging in the graph side of the view. Then set the "attractive-forces-from-graph" switch to "on."
7. Try replicating the graph on the right.
8. When you're ready, switch the MOUSE-INTERACTION chooser to "none - let particles move"
9. Observe the model for a while. Record your observations on the following step.

While conducting the experiment described in the previous step, answer the questions below:

Using the same model, try to replicate what you watched in the video with alcohol and nail polish.

Now that we've completed a number of explorations about how forces such as gravity, as well as forces between particles change the way particles behave, answer the questions below:

You should now be feeling more comfortable with how particles interact with one another. In particular, we've spent a lot of time experimenting with how particles in a gaseous state interact and how properties such as pressure and temperature emerge from those interactions. You've also been introduced to a model that shows how particles in a liquid state act differently than those same particles in a gaseous state. In this activity, we'll begin to theorize about how particles might shift between the liquid and gas state.

Consider how you might model evaporation and boiling?

Read the brainstorm topic below, then write your response in the blank box.

Question: What causes boiling?

Predict: Watch the video below that shows an interesting phenomenon. Use your observations to answer the following questions.

Watch the liquid closely as the experimenter pushes and pulls on the syringe. Answer the following questions.

Question: How can we model boiling?

Model

As a group model to explain why changing the pressure of the air above the liquid might be changing whether the liquid boils or not.

1. As a class do this together: Label a piece of paper as “Syringe before”. Discuss how to use pennies and oyster crackers to represent air molecules and water molecules. Include a key to represent the type of molecules and the speed of the molecules.
2. Discuss as a class:  Should there be any water molecules in the air above the syringe? Is is possible some water has evaporated already?
3. As a group, make your own copy of the class consensus model for the “Syringe before” on a single piece of paper.
4. As a group, now label a new piece of paper as “Syringe after pulling”. Using the same number of pennies and oyster crackers, make a 2nd physical model showing the state of syringe when the plunger is pulled out and bubbles of water are forming and raising to the top of the liquid.
5. Discuss as a group:  Should there be the same number of water molecules in the air above the syringe as before?

Question: How can we model evaporation?

Consider the following experiment and its results. Then answer the questions below.

1. A group conducts an experiment to test the rate of evaporation in a closed vs, and open system. They gather the following supplies:
   • a cup with a small bit of rubbing alcohol in it
   • a petri dish
   • two eyedroppers
   • a clock
2. They fill two eyedroppers with rubbing alcohol and place two drops of alcohol on the table at the same time. They start the timer and immediately, cover one with a glass dish (see the photograph on the right)
3. They check every 1 hour to see if either drop has evaporated completely. At 2 hours, drop B in the open system has evaporated completely, but drop A in the closed system has not.
4. They continue for observing, now every hour, and at the end of the day (8 hours later), drop A still hasn't evaporated completely.