Embedded Files
Overview
Sensors, like the Circuit Playground, allow us to understand and describe the world around us, including chemical reactions taking place. As chemical reactions occur, bonds are broken and formed, resulting the release of energy as thermal energy and absorption of energy, stored as chemical potential energy. Reactions which overall release energy are referred to as exothermic, while reactions which overall absorb energy are called endothermic. The amount of energy absorbed or released by a reaction is dependent on the relative bond energies of the reactants and products. To aid students in visualizing the transfer of energy during chemical reactions, sensors can be used in tandem with visual figures (reaction diagrams) to model the relationship between total bond energy and the thermal properties of a chemical reaction.
Grade Level & Content Area:
Secondary Science (9th-12th)
Chemistry
Learning Objectives:
Students will be able to:
Develop a code which changes the color of LED lights on a sensor depending on the temperature of a system to illustrate the release or absorption of energy by a chemical reaction.
Design an "explanatory card" which depicts the relationship between the color of their sensor and the absorption/release of energy by a chemical reaction.
Relate the colors they observed to a reaction energy diagram of the chemical reaction they investigated, to produce a complete model of how bond energies relate to the energy released/absorbed by chemical reactions.
Standards:
Montana Physical Science (9th-12th) Standard: Students will develop a model to illustrate that the release or absorption of energy from chemical reaction is dependent upon changes in total bond energy. HS-PS1-4.
Supplies:
White Card Stock Paper (1 page per student)
Sealable Plastic Sandwich Bags
Tape
Colorful Markers (Red/Orange/Yellow/Light Blue/Dark Blue)
Fine-tipped Pens
Scissors
Independent thermometer
Circuit Playground Sensor & Cord (1 of each per student)
Computer or Chromebook with USB port (1 per student)
Coding the Sensor:
Setting up:
1) Go to: https://makecode.adafruit.com/ and select +New Project.
2) Connect the Circuit Playground to your computer via the microUSB to USB cord provided.
3) Select the gear at the top right corner of your browser to reveal a dropdown menu. [Image 1]
4) From the dropdown menu, select "Pair Device," which will open a pop-up window, from which you can select the Circuit Playground. You may need to press the reset button on the device.
5) From the green "Loop" section of the code menu, drag and drop a "forever" block. [Image 2]
6) Insert, from the light blue "Logic" section of the code menu, an "if true then... else..." block. [Image 3]
7) Click the plus button at the bottom left of the "if true then... else..." block to add another "else" slot.
Coding for Temperatures Above Room Temperature:
8) Within the first "if true then..." section, insert a comparison code from the "Logic" section. [Image 4]
9) Within this comparison code, insert a circular "Input" chunk, titled "Temperature (ºC)." [Image 5]
10) Select the comparison dropdown menu, and set the "Temperature (ºC)" chunk to be greater than or equal to the other circular input section.
11) In the other circular input section, set the value equal to 1 degree above the room temperature indicated by the independent thermometer.
12) In the slot below where you input the comparison code, insert a chunk from the "Light menu" titled "show ring." [Image 6]
13) Click on the red part of the inner ring, and then click each circle in the outer ring to set them to red.
Your ring should now light up red when exposed to temperatures above the measured room temperature.
Coding for Temperatures Below Room Temperature:
14) Within the "else if..." section, insert a comparison code from the "Logic" section. [Image 7 & Image 4]
15) Within this comparison code, insert a circular "Input" chunk, titled "Temperature (ºC)." [Image 5]
16) Select the comparison dropdown menu, and set the "Temperature (ºC)" chunk to be less than or equal to the other circular input section.
17) In the other circular input section, set the value equal to 1 degree below the room temperature indicated by the independent thermometer.
18) In the slot below where you input the comparison code, insert a chunk from the "Light menu" titled "show ring" [Image 6]
19) Click on the blue part of the inner ring, and then click each circle in the outer ring to set them to blue.
Your ring should now light up blue when exposed to temperatures below the measured room temperature.
Coding for Room Temperature:
20) In the final "else..." slot, insert a chunk from the "Light menu" titled "show ring" [Image 6]
21) Click on the white part of the inner ring, and then click each circle in the outer ring to set them to white.
Your ring should now light up white when exposed to temperatures within 1º of room temperature.
Testing your code:
To test if your code works, adjust the thermometer slider in the top right corner of box which contains an image of your sensor. As you move through the temperature ranges, you should see the simulated lights on the sensor
Image 1: Gear and dropdown menu
Image 2: Green forever block from "Loops"
Image 3: "If true then... else..." block from "Logic"
Image 4: Comparison chunk from "Logic"
Image 5: "Temperature in ºC" chunk from "Input"
Image 6: "Show ring" chunk from "Light"
Image 7: "Else if..." slot for low temp. code
Image 8: Thermometer for testing code
Creating the Explanatory Card:
1) On one piece of white card stock paper, outline the Circuit Playground twice, with enough room between each circle to fit your designs. [Image 1]
2) Around one circle, sketch an image associated with heat (e.g. a flame) that extends the upper half of the circle. [Image 2]
3) Around the other circle, sketch an image associated with cold that extends the lower half od the circle. For example, a snowflake or icicle. [Image 3]
Make sure your designs are not bigger than your plastic bags!
4) Using the scissors, cut out the two shapes that were drawn around the Circuit Playground outlines. [Image 4]
5) Color in your designs with warm colors for the image associated with heat, and cool colors for the image associated with cold.
6) Apply tape to the front side of the image associated with heat, and try to stay within the outline of the Circuit Playground. This will allow you to attach your cold image to your heat image to create a single backing for the sensor. [Image 5]
7) Write a mnemonic, or other phrase, which helps you remember the difference between endothermic and exothermic reactions. The mnemonic for exothermic reactions should be on the warm colored image, which will strengthen the association between the red LEDs and the flow of heat out of the reaction. Inversely, the mnemonic for endothermic reactions should be written on the image associated with cold, which will strengthen the association between the blue LEDs and the flow of heat into the reaction. [Image 6]
Example: Heat ENters the reaction = ENdothermic. Heat EXits the reaction = EXothermic.
8) Secure the cool colored image to the warm colored image by pressing the cool colored image on top of the tape that is secured to the front of the warm colored image. You have now created an explanatory backing card for the sensor.
9) Apply tape to the front of the explanatory card. This is how the sensor will be attached. [Image 7]
10) Firmly press the sensor against the tape on the front of the explanatory card.
11) Place the whole set-- sensor and explanatory card-- into a plastic bag and seal the bag well. Your sensor can now be placed into solution to detect changes in temperature. [Image 8]
Image 1: Tracing the sensor
Image 2: Creating the "hot" design
Image 3: Creating the "cold" design
Image 4: Cutting out the designs
Image 5: Coloring and Taping
Image 6: Writing a nmemonic
Image 7: Assembling the explanatory card
Image 8: Assembling and sealing the complete set
Expanding the Lesson:
Once the Circuit Playground sensor has been coded, the explanatory card has been designed, and the complete set has been assembled and sealed in a plastic bag, the sensor can now be used to detect and indicate the changes in temperature of chemical reactions.
Students can be provided with the supplies for two chemical reactions (one exothermic and one endothermic), whose reagents are at room temperature. The students will run the reactions with their sensors submerged in solution, and observe whether the temperature of the reaction increases or decreases as it proceeds. Based on their observations and the mnemonic on their explanatory card, the students will identify if the reaction was endothermic or exothermic. Finally, students will match the reaction diagrams with the associated chemical reactions, using their conclusion about the thermal properties of the chemical reactions based on their observations generated with the Circuit Playground sensor. By pairing the sensor data/code with the reaction diagrams (which indicate the bond energies of the reactants and products), students will produce a model that illustrates the relationship between total bond energy and heat absorbed or released by a chemical reaction.
Final Product
Below Room Temp.
Below Room Temp.
The LEDs are illuminated blue.
At Room Temperature
At Room Temperature
The LEDs are illuminated white.
Above Room Temp.
Above Room Temp.
The LEDs are illuminated red.
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