Conservation of Mass

1 collaborator

Kelly Ryan (Author)

Overview

1. Purpose:

This model demonstrates the Law of Conservation of Mass in a chemical reaction, specifically a synthesis reaction. Additionally, the model allows the user to explore the effect of concentration on the time the reaction takes and effect of varying the concentration of one or both of the reactants.

A + B -> AB

This model also addresses one of the next generation 8th grade science standards (MS-PS1-5). This standard directs us to develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved. The standard clarifies that emphasis is on law of conservation of matter and on physical models or drawings, including digital forms, that represent atoms. It further states that assessment does not include the use of atomic masses, balancing symbolic equations, or intermolecular forces.

2. Entities, State Variables, and Scales:

There are three entites ReactantA (A), ReactantB (B), and the Product (AB). Location is the primary variable of interest, as ReactantA (A) and ReactantB (B) will need to be on the same spot to react and create the Product (AB). The reaction time will vary depending on the initial concentrations of ReactantA (A) and ReactantB (B).

3. Process Overview and Scheduling:

Model ticks represent the passage of time. The reaction occurs when a molecule of ReactantA and a molecule of ReactantB share the same space. The reaction proceeds until either ReactantA or ReactantB are used up.

Design Concepts

4. Design Concepts

DETAILS

5. Initialization:

In the set-up the area is cleared and the ticks are reset. The shape, color, size and number of ReactantA and ReactantB are set. The shape and color of the Product is also set.

6. Input Data:

The number of molecules of ReactantA and ReactantB are controlled by the user with sliders.

7. Submodels:

One submodel is required. The "react" submodel occurs when a ReactantA molecule and a ReactantB molecule share the same space. The reactants then disappear and the product is created.

REFERENCE

Ryan, K. (2013). kellyryanscience@gmail.com

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Click to Run Model

breed [reactantAs reactantA] ; this is a synthesis reaction with two reactants and one product
breed [reactantBs reactantB]
breed [products product]

to setup
  clear-all ; clear.
  set-default-shape reactantAs "circle" ; set shapes for the three turtles.
  set-default-shape reactantBs "circle"
  set-default-shape products "circle molecule"
  
  create-reactantAs amount-of-reactantA ; slider reactantA sets number of green reactantA turtles, placed randomly.
    [set color green
      set size 1
      setxy random-xcor random-ycor]
  create-reactantBs amount-of-reactantB ; slider reactantB sets number of blue reactantB turtles, placed randomly.
    [set color blue
      set size 1
      setxy random-xcor random-ycor]
  reset-ticks ; resets ticks.
end 

to go ; begins reactant behavior.
  ask turtles 
    [right random-float 15 - random-float 15 fd 1] ; turtles move randomly.
    if count reactantAs = 0 [show "reaction complete!" stop] 
    ; checks if reactantA is gone, gives message to observer, and stops reaction.
    if count reactantBs = 0 [show "reaction complete!" stop] 
    ; checks if reactantB is gone, gives message to observer, and stops reaction.
  react ; calls sub-routine react.
  tick ; adds one tick.
end 

to react ; sub-routine which allows the reactants to create a product.
  ask one-of reactantAs ; asks one of the reactantAs to determine if it shares a space with a reactantB.
    [if any? reactantBs in-radius 1
    [set breed products ; if reactantA and reactantB share the same space, reactantA becomes the product with size 2.
      set size 2
     ask one-of reactantBs in-radius 1 [die]]]; at the same time as reactantA becomes the product, reactantB dies.
end 

; kellyryanscience@gmail.com

There is only one version of this model, created about 12 years ago by Kelly Ryan.

Attached files

File	Type	Description	Last updated
Conservation of Mass.png	preview	Preview for 'Conservation of Mass'	about 12 years ago, by Kelly Ryan	Download

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