Spartan Luminol: Difference between revisions

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This space is intended to describe the demonstration that is here. Please use this space to describe in short the demonstration, making sure to mention here if it will require any additional safety equipment or how easily it can be adjusted for varied grade levels.
This is a classic Luminol demonstration with the addition of some MSU Spartan pride. The solutions should be prepared at least 8 hours in advance. However, they don't have a long shelf life, so don't rely on any solutions that are 3 months old or older.
Use this page as a base layout for editing the wiki. Feel free to copy the layout onto other pages, and to put the content as needed into the page.


== Materials ==
== Materials ==
Line 59: Line 58:


== Why This Works ==
== Why This Works ==
'''''COMING SOON'''''
 
<!-- ===Short Explanation===
===Short Explanation===
This is where you would provide a basic, easy-to-understand explanation of the demonstration. Try not to use too much "Science Jargon", and if needed add any explanation tips, like comparing the demo to something kids are familiar with.
''Chemilluminescence'' is when a chemical reaction produces light. The reaction does not have to emit heat, like when a reaction creates fire, but gives off light without being hot. For our reaction, we have a luminol solution mixing with a hydrogen peroxide solution. the hydrogen peroxide reacts with the luminol and causes it to release energy, which it does so by emitting light. If you were to touch the tubes while the reaction happened, they wouldn't be warm at all, even though they are glowing!
 
This kind of reaction is not very common in chemistry, but it is a reaction that we are all pretty familiar with. Glow sticks use a luminol reaction, by having the two solutions mix together in a small sealed tube. When you crack a glow stick, you are actually breaking a tiny glass tube inside the glow stick. This tube contains a hydrogen peroxide solution, which reacts with the glowing solution around it. Fireflies, or lightning bugs, also use chemilluminescence. When a firefly glows, it has a similar reaction happen inside of its abdomen, which causes a small burst of light. Fireflies create their lights in order to communicate, and each species of firefly uses a different flashing pattern!


===Full Explanation===
===Full Explanation===
This is where you will explain the demonstration in full, and provide all additional information that pertains to the demo. Unlike the short explanation above, this should be worded so someone who is familiar with the topics might understand it. If needed, you can provide equations and citations for additional sources of information on the topic. This is also where you will find some answers for trickier questions, such as "How does a plane fly upside-down?" for the Bernoulli's Principle demo. If you want to add a floating box for equations, copy the following:
''Chemilluminescence'' is when a reaction produces light without also being exothermic. The release of ''chemical'' energy in the reaction excites the electrons in the atoms and molecules, and they go to a higher energy level. The electrons then drop to a lower energy level, emitting a photon in the process. This type of reaction is uncommon, as most reactions that produce light do so by blackbody radiation. ''Blackbody Radiation'' is when the electrons in an atom or molecule are excited and go to a higher energy level due to ''thermal'' energy. When they drop back to a lower energy level, they produce light.


{| class="wikitable" style="color:black; background-color:#ddd; text-align: center; margin: auto"
The Luminol reaction goes through three major steps. When the solutions are first prepared, the sodium carbonate create a basic solution, and luminol reacts with it:
| This will give you
{| class="wikitable" style="color:black; background-color:#ddd; text-align: left; right-margin: auto"
| a floating box.
| Na<sub>2</sub>CO<sub>3</sub> + H<sub>2</sub>O
| '''→'''
| 2 Na<sup>+</sup> + 2 OH<sup>-</sup> + H<sub>2</sub>CO<sub>3</sub>
|-
|-
| The box will be
| C<sub>8</sub>H<sub>7</sub>O<sub>3</sub>N<sub>3</sub> + 2 OH<sup>-</sup>
| centered for you.
(Luminol)
| '''→'''
| C<sub>8</sub>H<sub>5</sub>O<sub>3</sub>N<sub>3</sub><sup>2-</sup> + 2 H<sub>2</sub>O
(Luminol Dianion)
|}
|}
It is worth noting that the sodium bicarbonate in solution acts to buffer the carbonic acid (H<sub>2</sub>CO<sub>3</sub>) being produced, keeping the solution basic.


== Demonstration ==
When the two solutions are mixed, the hydroxide decomposition is catalyzed in a two step reaction by the Copper salt anion:
{| class="wikitable" style="color:black; background-color:#ddd; text-align: left; right-margin: auto"
| 2 H<sub>2</sub>O<sub>2</sub> + (2 SO<sub>4</sub><sup>2-</sup>) or (2 Cl<sup>-</sup>)
| '''→'''
| 2 H<sub>2</sub>O + (2 SO<sub>3</sub><sup>-</sup> + 2 O<sub>2</sub>) or (2 ClO<sup>-</sup>)
|-
| 2 H<sub>2</sub>O<sub>2</sub> + (2 SO<sub>3</sub><sup>-</sup>) or (2 ClO<sup>-</sup>)
| '''→'''
| 2 H<sub>2</sub>O + (2 SO<sub>4</sub><sup>2-</sup>) or (2 Cl<sup>-</sup> + 2 O<sub>2</sub>)
|}


Use approximately equal amounts of A1 and A2. If taking out into the audience, make sure the solution is stoppered! To run the Spartan S, you need to put one tube into A1 bottle, one tube into A2 bottle (make sure the tubes are clean before you do this, you can run them with water beforehand to make sure). Then, but the stopper on top of a LARGE filter flask and pull a vacuum. WATCH the filter flask to make sure it doesn't get too full of solution. BEFORE you turn off the vacuum, pull out the tubes from A1 and A2, otherwise you will get backwash and it will ruin the rest of your solutions. Put both tubes in a solution of water and pull water through the S to clean it, then pull air.
The O<sub>2</sub> produced then reacts with the luminol dianion, replacing the Nitrogen and producing light:
 
{| class="wikitable" style="color:black; background-color:#ddd; text-align: left; right-margin: auto"
== What to Say ==
| C<sub>8</sub>H<sub>5</sub>O<sub>3</sub>N<sub>3</sub><sup>2-</sup> + O<sub>2</sub>
 
| '''→'''
If presented along with several other chemical demonstrations, you may wish to begin by highlighting the novelty of chemiluminesence. Ask the audience what types of things chemical reactions can do. Ask them what types of things they have seen reactions do earlier in your performance, if applicable. They might tell you that reactions can produce heat, as in elephant toothpaste, or eat away at things, as in rip-the-can. Well, chemical reactions can also produce light!
| C<sub>8</sub>H<sub>5</sub>O<sub>5</sub>N<sup>2-</sup> + N<sub>2</sub> + Light
 
|}
For very young audiences: "Chemiluminescence is a very special type of chemical reaction that produces lots of light. In this case, we are combining a chemical called luminol with one called hydrogen peroxide. Hydrogen peroxide is just the stuff you keep in your bathroom to clean cuts! When you mix these two chemicals, with a few other helper chemicals, the hydrogen peroxide gives energy to the luminol - it makes it excited. It's kind of like how eating a lot of candy gives you energy and makes you bounce around! Luminol is a chemiluminescent chemical, which just means that it likes to get rid of this extra energy by glowing - it makes light!"
 
This demonstration scales well to more advanced audiences. For high schoolers who may be familiar with the Bohr model, explain how electronic transitions produce photons (see the Why It Is) section and briefly describe why only very special reactions are chemiluminescent.
 
== Why It Is ==
 
Chemiluminescence is a rare effect. Most light we see in nature is produced by very hot objects. For instance, the sun and incandescent light bulbs are both very hot objects that emit light through a process called blackbody radiation. In blackbody radiation, thermal energy excites electrons in atoms or molecules to higher energy levels, which then fall back into lower energy levels and use the energy difference to release a photon of light.
 
Chemiluminescence causes involves transitions causing photons to be released, but the mechanism is very different than blackbody radiation. Rather than heat (thermal energy), chemical reactions provide the energy for electrons to reach higher energy levels in the molecules of a chemiluminescent solution. In this case, the chemical reaction involves the luminol being oxidized by the hydrogen peroxide. A variety of different reactions with luminol can be used, producing different color emission (see Reference 1).
 
So why don't all exothermic (energy-releasing) reactions produce chemiluminescence? Certain factors must be satisfied. The exothermic reaction must produce a molecule for which excited states can be occupied - not all molecules have these. Moreover, the probability for the molecule to be produced in this excited state must be greater than the probability of it to be produced in the ground state. Finally, the molecule in the resultant solution must be disposed to releasing photons via electronic transitions and must do so at a high rate to produce an easily-visible amount of light. The specific conditions of these characteristics is quite complicated.
 
Do not confunse chemiluminescence with phosphoresence or fluorescence. In those other processes, light is only emitted following the absorption of light. Phosphorescent or fluorescent reactions do not "glow in the dark," they must be illuminated by photons to then produce photons.
 
== Real Life Examples ==


Fireflies have enzymes that act on a luciferin substrate to produce their chemiluminescent effect. Many other types of organism, including some bacteria and algea, have similar abilities.
Although the peroxide decomposition produces a small amount of heat, it isn't enough to generate the light at the end. The light produced is from the replacement of nitrogen with oxygen, which leaves extra chemical energy in the luminol dianion and excites the electrons on the oxygen. when the electrons release this energy, they release it as light.


Lightning is also a chemiluminescent effect. It is an electrical discharge in the atmosphere that excites electrons in the gas molecules in air, which then fall back down and produce photons. Lightning also dissassociates diatomic nitrogen and oxygen, which can then release photons when they recombine.
This reaction can be found in nature, such as with fireflies using luciferin and the enzyme luciferase to produce light in their abdomens. This reaction is also commonly used as a novelty with glowsticks. Inside a glowstick is a small glass cylinder which contains a peroxide solution. when you bend a glowstick, you break this cylinder and let the peroxide react with the solution around it, producing light!


-->
== Additional Information ==
== Additional Information ==


* This demonstration pairs well the [[Fluorescence]] demonstration.
* This demonstration pairs well the [[Fluorescent Liquids]] demonstration, as a way to compare the effects.

Latest revision as of 18:01, 18 August 2016

Chemistry, Biology: Chemilluminescence
Grade Range: Elementary School, Middle School, High School
Format: Stage

This is a classic Luminol demonstration with the addition of some MSU Spartan pride. The solutions should be prepared at least 8 hours in advance. However, they don't have a long shelf life, so don't rely on any solutions that are 3 months old or older.

Materials

  • 2000 mL Vacuum Flask with Tube Cork
  • Vacuum Pump
  • Spartan "S" Board
  • 500 mL Bottle (for Water)
Solution A
  • Luminol
  • Sodium Carbonate
  • Sodium Bicarbonate
  • Ammonium Carbonate monohydrate
  • Copper (II) Sulfate OR Copper (II) Chloride
  • Water
  • 1000mL Brown Bottle or similar
Solution B
  • Hydrogen Peroxide
  • Water
  • 1000mL Brown Bottle or similar

Safety Precautions

Please read the Dry Chemical and Liquid Chemical sections of the Demonstration Safety page before performing this demonstration.

This demonstration requires: Safety Glasses, Gloves

Demonstration

Preparation

Solution A: Mix the following chemicals into 500 mL of DI water in order, stirring constantly. Do not add the next chemical until the one prior is fully dissolved. Mix these chemicals either within a dark bottle or in a room with the lights dimmed, as some of them are light sensitive.

  • 4.0g Sodium Carbonate
  • 0.2g Luminol (3-aminophthalhydrazide)
  • 24g Sodium Bicarbonate
  • 0.5g Ammonium Carbonate Monohydrate
  • 0.4g Copper (II) Sulfate OR 0.25g Copper (II) Chloride

Once all of the chemicals are in solution, add 500mL of DI water to dilute fully. Store in an airtight brown bottle or similar, and label with the Demonstration name, Solution A, and date, as well as your initials.

Solution B: Dilute 5mL of the 30% Hydrogen Peroxide with 1L of DI water. Store in an airtight brown bottle or similar, and label with the Demonstration name, Solution B, and date, as well as your initials.

Presentation
  1. Set up the Spartan "S" board, and connect the single ended tube to the tube cork. Put the tube cork on the vacuum flask, and connect it to the vacuum pump.
  2. Show the audience the two solutions, and ask them if they have seen fireflies before. Can anyone guess how a firefly lights up? Explain that there is a chemical reaction, much like the one that will happen between the two solutions you have.
  3. Put the double ended tube into the two solutions. Explain that the two chemicals will react when they mix and produce light. Ask for a countdown, and at the end flip the switch on the vacuum pump.
  4. Watch as the solutions are pulled through the tubing and start to glow! The vacuum pump will pull the solutions pretty quickly, so make sure to watch the bottles for when they run out.
  5. After explaining the demonstration, put both of the ends on the double ended tube into the water bottle. Vacuum the water through the tubing to clean it, and then let the vacuum run for a minute to pull air through and dry the tubing. The end solution can be poured safely down a drain.

Why This Works

Short Explanation

Chemilluminescence is when a chemical reaction produces light. The reaction does not have to emit heat, like when a reaction creates fire, but gives off light without being hot. For our reaction, we have a luminol solution mixing with a hydrogen peroxide solution. the hydrogen peroxide reacts with the luminol and causes it to release energy, which it does so by emitting light. If you were to touch the tubes while the reaction happened, they wouldn't be warm at all, even though they are glowing!

This kind of reaction is not very common in chemistry, but it is a reaction that we are all pretty familiar with. Glow sticks use a luminol reaction, by having the two solutions mix together in a small sealed tube. When you crack a glow stick, you are actually breaking a tiny glass tube inside the glow stick. This tube contains a hydrogen peroxide solution, which reacts with the glowing solution around it. Fireflies, or lightning bugs, also use chemilluminescence. When a firefly glows, it has a similar reaction happen inside of its abdomen, which causes a small burst of light. Fireflies create their lights in order to communicate, and each species of firefly uses a different flashing pattern!

Full Explanation

Chemilluminescence is when a reaction produces light without also being exothermic. The release of chemical energy in the reaction excites the electrons in the atoms and molecules, and they go to a higher energy level. The electrons then drop to a lower energy level, emitting a photon in the process. This type of reaction is uncommon, as most reactions that produce light do so by blackbody radiation. Blackbody Radiation is when the electrons in an atom or molecule are excited and go to a higher energy level due to thermal energy. When they drop back to a lower energy level, they produce light.

The Luminol reaction goes through three major steps. When the solutions are first prepared, the sodium carbonate create a basic solution, and luminol reacts with it:

Na2CO3 + H2O → 2 Na+ + 2 OH- + H2CO3
C8H7O3N3 + 2 OH-

(Luminol)

→ C8H5O3N32- + 2 H2O

(Luminol Dianion)

It is worth noting that the sodium bicarbonate in solution acts to buffer the carbonic acid (H2CO3) being produced, keeping the solution basic.

When the two solutions are mixed, the hydroxide decomposition is catalyzed in a two step reaction by the Copper salt anion:

2 H2O2 + (2 SO42-) or (2 Cl-) → 2 H2O + (2 SO3- + 2 O2) or (2 ClO-)
2 H2O2 + (2 SO3-) or (2 ClO-) → 2 H2O + (2 SO42-) or (2 Cl- + 2 O2)

The O2 produced then reacts with the luminol dianion, replacing the Nitrogen and producing light:

C8H5O3N32- + O2 → C8H5O5N2- + N2 + Light

Although the peroxide decomposition produces a small amount of heat, it isn't enough to generate the light at the end. The light produced is from the replacement of nitrogen with oxygen, which leaves extra chemical energy in the luminol dianion and excites the electrons on the oxygen. when the electrons release this energy, they release it as light.

This reaction can be found in nature, such as with fireflies using luciferin and the enzyme luciferase to produce light in their abdomens. This reaction is also commonly used as a novelty with glowsticks. Inside a glowstick is a small glass cylinder which contains a peroxide solution. when you bend a glowstick, you break this cylinder and let the peroxide react with the solution around it, producing light!

Additional Information

  • This demonstration pairs well the Fluorescent Liquids demonstration, as a way to compare the effects.
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