## October’s Halloween STEM Challenges, Part 2: Electrons, Batteries, LEDs, and Simple Circuits

### DAY 2

STUDENT’S NOTES FROM THE CIRCUIT PROGRAM

Student notes were taken to remember what they learned about simple circuits and their paper circuit project.

Simple Circuits with Meghan Thoreau, OSU Extension Educator, and Judy Walley, Teays Valley Chemistry Teacher. Full presentation link: go.osu.edu/simplecircuits

#### Why Understanding Simple Circuits is Important?

Basic circuit knowledge is important for many different disciplines, including engineering, physics, chemistry, and mathematics. It’s also useful knowledge around this time of year when you may need to repair a string of old holiday lights? Understanding and building simple circuits show us important concepts learned in school that can describe useful real-world systems, like devices we use every day, cell phones, light switches, Chromebooks, cars, etc.

The electric charge that flows through your house is called your electric circuit. This carries useful energy through your house that you can transform into other forms of energy to do various tasks. The US standard household circuit has an effective voltage that takes 120-volts. Volts represent the energy per unit charge. We discussed these basic building blocks of simple circuits in STEM Club this month. Our hands-on simple circuit design challenge uses 3-volt lithium batteries. Before jumping into our design challenges we’ll cover a few basic circuitry concepts and energy principles.

#### Conservation of Energy, First Law of Thermodynamics

The conservation of energy principle was discovered and published by Julius Robert von Mayer in 1842. Mayer was a German physicianchemist, and physicist and one of the founders of thermodynamics. However, there were many others working in the field that made significant contributions, such as, James Prescott JouleHermann von Helmholtz,  Alessandro Volta, and Benjamin Thomson.

The principle of conservation of energy is an effective tool in solving problems and understanding how different forms of energy directly impact our lives. There are also benefits to this principle. These include recycling of materials, lower energy costs for consumers, less pollution due to a reduction in the use of fossil fuels, and less harm to animals and the environment. We watched a short video, from Two Minute Classroom, that explained the basic concepts of how energy transforms itself into other forms and never truly disappears or is destroyed.

Below are 10 common types of energy:

#### Atoms and Electrons

Judy Walley led students through the basic concepts of atoms and electrons, because, without the flow of electrons, we have no electric circuit to work with.

Judy Walley explains the basic concepts of atoms and electrons as students formed a single circuit where electrons passed through them to power a sound buzzer.

Walley also explained the chemistry of a battery and how chemical reactions occur inside the battery that causes an imbalance or a build-up of electrons (-) on one side of the battery over the other, hence why one side or one terminal of the battery is negative (-) and the other positive (+). We also introduced the basic materials for our hands-on design challenges and explain how a battery works.

Screenshot from our virtual simple circuit presentation.

How a Battery Works

Batteries are important to everyday life. Batteries are essential to most electrical devices. They exist in our cars, cell phones, laptops, and other electronic appliances, and serve as critical backup sources of electricity in telecommunications, public transportation, and medical devices. A battery is essentially a container full of chemicals that produce electrons (-). Inside the battery itself, a chemical reaction produces the electrons.

The battery is a device that stores chemical energy and converts it to electrical energy. The chemical reactions in a battery involve the flow of electrons from one material (electrode) to another, through an external circuit. The flow of electrons provides an electric current that can be used to do work. In our case, students use copper tape to build a paper circuit to create light energy with an LED. Below depicts the inner wors of a battery.

Screenshot of how a battery works from our virtual simple circuit presentation.

The students learned that a battery has three main parts: an anode (-), cathode (+), and the electrolyte that separates the two terminal ends on the battery. We discussed the chemical reaction happening inside the battery that causes electrons (-) to build up on one side of the battery causing one end to be negatively charged (-) and the other end positively charged (+). This buildup causes an imbalance of electrons (-), that want to travel to the other side of the battery, but can’t move freely until a conductive circuit is completely looped for the electrons to travel through; in our case, the conduit is copper tape.

When a circuit is complete, or a loop created, the electrons will flow through the conductive paths racing to reach the other side of the battery terminal. When the electrons flow through the loop, the chemical energy inside the battery is transformed into electrical energy running through the circuit. When all electrons (-) make it to the other side, the battery stops working. All of the electric energy was transformed into other forms of energy.

Electrical energy allows us to do work by transforming energy into other forms. We use LEDs in our paper circuit design challenge because it’s a simple way to show how electric energy is transformed or converted into light energy. We could replace the LED with a simple motor and the motor would convert electrical energy into kinetic.

Screenshot of simple circuit components and electricity concepts from our virtual simple circuit presentation.

#### What’s a Diode?

Both LEDs and motors can easily be added to simple circuits. However, LEDs are somewhat more restrictive than motors, because LEDs are diodes. A diode only allows current to flow in one direction. From the cathode, (-) leg of the LED through the anode (+) leg. Note that the anode on a battery is negatively charged, but the anode on an LED is positively charged! The correct way to connect an LED legs to the battery terminals is positive to positive/anode to cathode and negative to negative/ cathode to anode. Study the image above if this is confusing. If the LED or battery is flipped in the wrong configuration then no current or electrons flow through the LED because the diode only allows for current to flow in one direction.

Image source: https://diotlabs.daraghbyrne.me/docs/controlling-outputs-motors/diodes/

A motor does not have a diode, therefore current can flow in either direction, and depending on how the motor is connected to the battery will decide what direction the motor turns left/right, or moves forwards/backward.

Image source: https://www.robotroom.com/DPDT-Bidirectional-Motor-Switch.html

#### Electric Circuit Design Challenges

As a virtual group, we challenged ourselves with a few NearPod activities to reinforce our electricity concepts before beginning our hands-on paper circuit challenges. A paper circuit is a functioning electronic circuit built on a paper surface instead of a printed circuit board (PCB). Projects can range from greeting cards to origami, to traditional art such as paintings or drawings. STEM totes went home with the students and included paper circuit design challenges and supplies.

Supply List (we purchased all our supplies through Amazon)

• LED
• Conductive copper tape
• Plain card stock, or templates printed on card stock
• 3-V coin cell battery
• Tape (not included)
• Binder Clip

Other useful items: multicolor/print card stock, glue stick, scissors, pencils, markers

Teays Valley High school mentor, Julia Kudar, assisting elementary students with our paper circuits program.

## October’s Halloween STEM Challenges, Part 1: Science of Color, Vision, and Phosphorescent

We covered a lot of material last month. We thought we’d take advantage of the spooky mystery themes of Halloween and challenge our students to become science detectives, experimenting with hands-on activities involving chromatography, perception of vision, and phosphorescent slime chemistry. We also learned about atoms, electrons, batteries, LEDs, and simple circuits.

### Chromatography

The students became CSI lab technicians, tasked with solving a who-done-it pumpkin theft. All that was left at the scene of the crime was a letter demanding cookies! No fingerprints were found, but six suspects were brought in for questioning and all six had different black markers on their person. The marker evidence was tagged and brought to the CSI lab along with the random letter for further analysis. Marker samples were taken and a chromatography test was performed by our young lab technicians.

Chromatography is a laboratory technique for the separation of a mixture (more specifically separation of molecules) and in our case black marker ink molecules. The ink was dissolved in a water solution process of mobile to stationary phase, revealing distinct ink-finger prints for comparative analysis against an ink sample taken from the random note. The students discovered different ink molecules travel at different speeds, causing them to separate and reveal distinct color patterns that could help identify the pumpkin thief from the six suspects.

People don’t often pick up a marker or pen and think of molecules,  but ink and paints are made up of atoms and the molecules, like everything, follow rules. Ink and paints follow the standard CPK rule, which is a popular color convention for distinguishing atoms of different chemical elements in molecular modeling (named after the chemists Robert Corey, Linus Pauling, and Walter Koltun). Basically, certain elements are associated with different colors. For example,

• Hydrogen = White
• Oxygen = Red
• Chlorine = Green
• Nitrogen = Blue
• Carbon = Grey
• Sulphur = Yellow
• Phosphorus = Orange
• Other = Varies – mostly Dark Red/Pink/Maroon

Teays Valley High school mentor, Drew Dean, assists elementary students with our chromatography lab.

PERSISTENCE OF VISION

Persistence of vision refers to the optical illusion that occurs when visual perception of an object does not cease for some time after the rays of light proceeding from it have ceased to enter the eye. The discovery was first discussed in 1824 when an English-Swiss physicist named Peter Mark Roget presented a paper, “Explanation of an Optical Deception in the Appearance of the Spokes of a Wheel when seen through Vertical Apertures” to the Royal Society in London. Shortly after, in 1832, a Belgian physicist Joseph Plateau built a toy that took advantage of the optical illusion trick. (Photo below source: http://streamline.filmstruck.com/2012/01/07/the-persistence-of-persistence-of-vision/)

The toy made images move independently but overlapped them or when placed in a series made them look as if they were walking, running, juggling, dancing. This concept soon laid the foundation for early filmmaking. (Photo below source be: http://1125996089.rsc.cdn77.org/wp-content/uploads/2011/12/persistence-of-vision-transit.jpg)

The students learned how our eyes report basic imaginary back to the brain, or rather how our eyes perceive shapes, their motion, and their relative position from other objects. The students discovered that eyes are not simple windows to the world. Eyes do not see what is, but instead, see approximations.

PHOSPHORESCENT SLIME

The students learned how different objects glow in the dark. First, students learned that heat is a good emitter of light, such as a fire or an old-fashioned light bulb, but heat isn’t always required to make something appear to glow. For example, bedroom glow-in-the-dark stickers, glow sticks, or fireflies do not require heat. The stickers and even certain types of rocks, like the Bologna Stone, require several hours of light to charge them in order to later glow. But glow sticks and fireflies, do not require heat or light, but instead, deal with chemistry where two different elements are mixed together to make a ‘luminescent’ compound.

We talked about phosphorescence and the process in which energy absorbed by a substance is released slowly in the form of light. Unlike the relatively swift reactions in fluorescence, such as those seen in a common fluorescent tube, phosphorescent materials “store” absorbed energy for a longer time, as the processes required to re-emit energy occur less often.

Finally, we let the students become chemists and make their own phosphorescent slime for later glow in the dark fun after the compound was charged by light. The young chemists used measuring devices to concoct their spooky slime recipe.

Make another batch at home with your young chemist:

1. Add 20.0 mL of glue to cup
2. Add 15.0 mL of water to cup
3. STIR!
4. Drop of preferred food coloring
5. STIR!
6. Add a drop of glow in the dark phosphorescence paint
7. Add 12.0 mL of BORAX solution
8. STIR! It will be runny until you take it out of the cup and start to play with it.