Cool Blue Light Chemiluminescence Experiment

Sunday September 20, 2015

Glow sticks generate light with very little heat, just like the glow you see from fireflies, jellyfish, and a few species of fungi. Chemiluminescence means light that comes from a chemical reaction. When this happens in animals and plants, it’s called bioluminescence.


In a glow stick, when you bend it to activate it, you’re breaking a little glass tube inside which contains hydrogen peroxide (H2O2). The tube itself is filled with another chemical (phenyl oxalate ester and a fluorescent dye) that is kept separate from the H2O2, because as soon as they touch, they begin to react. The dye in the light stick is what gives the light its color.


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Special Science Teleclass: Chemistry

Monday December 8, 2014

This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I’ve included it here so you can participate and learn, too! (Click here if you’re looking for the more recent version that also includes Chemical Engineering.)


When you think of slime, do you imagine slugs, snails, and puppy kisses? Or does the science fiction film The Blob come to mind? Any way you picture it, slime is definitely slippery, slithery, and just plain icky — and a perfect forum for learning real science. But which ingredients work in making a truly slimy concoction, and why do they work? Let’s take a closer look…


Materials:


  • Sodium tetraborate (also called “Borax” – it’s a laundry whitener) – about 2 tablespoons
  • Clear glue or white glue (clear works better if you can find it) – about 1/2 cup
  • Yellow highlighter
  • Pliers or sharp razor (with adult help). (PREPARE: Use this to get the end off your highlighter before class starts so you can extract the ink-soaked felt inside. Leave the felt inside highlighter with the end loosely on (so it doesn’t dry out))
  • Resuable Instant Hand Warmer that contains sodium acetate (Brand Name: EZ Hand Warmer) – you’ll need two of these
  • Scissors
  • Glass half full of COLD water (PREPARE: put this in the fridge overnight)
  • Mixing bowl full of ice (PREPARE: leave in freezer)
  • Salt
  • Disposable aluminum pie place or foil-wrapped paper plate
  • Disposable cups for solutions (4-6)
  • Popsicle sticks for mixing (4-6)
  • Rubber gloves for your hands
  • Optional: If you want to see your experiments glow in the dark, you’ll need a fluorescent UV black light (about $10 from the pet store – look in cleaning supplies under “Urine-Off” for a fluorescent UV light). UV flashlights and UV LEDs will not work.
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Mystifying Superconductor Roller Coaster

Thursday November 24, 2011

When I was in 10th grade, my teammate and I designed what we thought was pretty clever: a superconductor roller coaster, which we imagined would float effortlessly above its magnetic track. Of course, our roller coaster was only designed on paper, because yttrium barium copper oxide ceramics had only just been discovered by top scientists.



Did you notice how it was smoking in the video? That’s because it was so cold! The usual problem with superconductors is that they need to be incredibly cold in order to exhibit superconductive properties.  Yttrium barium copper oxide (YBa2Cu3O7) was the first compound that used liquid nitrogen for cooling, making superconductors a lot less expensive to work with – you no longer needed a cryogenic lab in order to levitate objects above a magnet.



Recently, scientists have found a way to make an amazing superconductor by taking a single crystal sapphire wafer and coating it with a thin (~1µm thick) ceramic material (yttrium barium copper oxide). Normally, the ceramic layer has no interesting magnetic or electrical properties, but that’s when you’re looking at it at room temperature. If you cool this material below -185ºC (-301ºF), it turns out that the ceramic material becomes a superconductor, meaning that it conducts electricity without resistance, with no energy loss. Zero. That’s what makes it a ‘superconductor’.


To further understand superconductivity, it’s helpful to understand what normally happens to electricity as it flows through a wire. As you may know, energy cannot be created or destroyed, but can be changed from one form to another.


In the case of wires, some of the electrical energy is changed to heat energy. If you’ve ever touched a wire that had been in use for a while, and discovered it was hot, you’ve experienced this. The heat energy is a waste. It simply means that less electricity gets to its final destination.


This is why superconductivity is so cool (no pun intended.) By cooling things down to temperatures near absolute zero, which is as low as temperatures can get, you can create a phenomenon where electricity flows without having any of it converted to heat.


Why do superconductors float above magnets?

Scientists also figured out that superconductors and magnetic field really do not like each other. The Meissner effect happens when a superconductor expels all its magnetic fields from inside.


However, if you make your superconductor thin enough, you can get the magnetic field to penetrate in discrete quantities (this is real quantum physics now) called flux tubes (the blue lines that go through the disc).


Inside each of the magnetic flux tubes, the superconductivity is destroyed, but the superconductor tries to keep the magnetic tubes pinned in weak areas and any movement of the superconductor itself (like if you pushed it) causes the flux tubes to move, and this is what traps (or locks) the superconductor in midair.



If you’d like to experiment with superconductors yourself, check out this information.


‘Molecules’ Exercises

Sunday January 10, 2010

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.


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Answers to ‘Molecules’ Exercises

Sunday January 10, 2010

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!


Here’s printer-friendly versions of the exercises and answers for you to print out: Simply click here for printable questions and answers.


Answers:
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‘Chemical Kinetics’ Exercises

Sunday January 10, 2010

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.


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Answers to ‘Chemical Kinetics’ Exercises

Sunday January 10, 2010

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!


Here’s printer-friendly versions of the exercises and answers for you to print out: Simply click here for printable questions and answers.


Answers:
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How to Not Burn Your Eyeballs and Lose Your Fingers

Sunday January 10, 2010

Chemical Data & Safe Handling Information Sheet

What do I really need to know first? First of all, the chemicals in this set should be stored out of reach of pets and children. Grab the chemicals right now and stuff them in a safe place where accidents can’t happen. Do this NOW! When you’re done storing your chemicals out of reach, come back and download this Chemical Safety Sheet AND watch this video.



 


Click here to Download the Chemical Safety Information!

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Hidden Carbon Dioxide

Sunday January 10, 2010

If you’ve ever burped, you know that it’s a lot easier to do after chugging an entire soda. Now why is that?


Soda is loaded with gas bubbles — carbon dioxide (CO2), to be specific. And at standard temperature (68oF) and pressure (14.7 psi), carbon dioxide is a gas. However, if you burped in Antarctica in the wintertime, it would begin to freeze as soon as it left your lips. The freezing temperature of CO2 is -109oF, and Antarctic winters can get down to -140oF. You’ve actually seen this before, as dry ice (frozen burps!).


Carbon dioxide has no liquid state at low pressures (75 psi or lower), so it goes directly from a block of dry ice to a smoky gas (called sublimation). It’s also acidic and will turn cabbage juice indicator from blue to pink. CO2 is colorless and odorless, just like water, but it can make your mouth taste sour and cause your nose to feel as if it’s swarming with wasps if you breathe in too much of it (though we won’t get anywhere near that concentration with our experiments).


The triple point of CO2 (the point at which CO2 would be a solid, a liquid, and a gas all at the same time) is around five times the pressure of the atmosphere (75 psi) and around -70oF. (What would happen if you burped then?)


What sound does a fresh bottle of soda make when you first crack it open? PSSST! What is that sound? It’s the CO2 (carbon dioxide) bubbles escaping. What is the gas you exhale with every breath? Carbon dioxide. Hmmm … it seems as if your soda is already pre-burped. Interesting.


We’ll actually be doing a few different experiments, but they all center around producing burps (carbon dioxide gas). The first experiment is more detective work in finding out where the CO2 is hiding. With the materials we’ve listed (chalk, tile, limestone, marble, washing soda, baking soda, vinegar, lemon juice, etc. …) and a muffin tin, you can mix these together and find the bubbles that form, which are CO2. (Not all will produce a reaction.) You can also try flour, baking powder, powdered sugar, and cornstarch in place of the baking soda. Try these substitutes for the vinegar: water, lemon juice, orange juice, and oil.


Materials:


  • baking soda
  • chalk
  • distilled white vinegar
  • washing soda
  • disposable cups and popsicle sticks
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Bouncy Ball

Sunday January 10, 2010

This is one of those 'chemistry magic show' type of experiments to wow your friends and family. Here's the scoop: you take a cup of clear liquid, add it to another cup of clear liquid, stir for ten seconds, and you'll see a color change, a state change from liquid to solid, and you can pull a rubber-like bouncy ball right out of the cup.

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Glowing Slime

Sunday January 10, 2010

When you think of slime, do you imagine slugs, snails, and puppy kisses? Or does the science fiction film The Blob come to mind? Any way you picture it, slime is definitely slippery, slithery, and just plain icky — and a perfect forum for learning real science.


But which ingredients work in making a truly slimy concoction, and why do they work? Let’s take a closer look…


Imagine a plate of spaghetti. The noodles slide around and don’t clump together, just like the long chains of molecules (called polymers) that make up slime. They slide around without getting tangled up. The pasta by itself (fresh from the boiling water) doesn’t hold together until you put the sauce on. Slime works the same way. Long, spaghetti-like chains of molecules don’t clump together until you add the sauce … until you add something to cross-link the molecule strands together.


The sodium-tetraborate-and-water mixture is the “spaghetti” (the long chain of molecules, also known as a polymer), and the “sauce” is the glue-water mixture (the cross-linking agent). You need both in order to create a slime worthy of Hollywood filmmakers.


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Turning Water into Wine

Sunday January 10, 2010

Phenolphthalein is a weak, colorless acid that changes color when it touches acidic (turns orange) or basic (turns pink/fuchsia) substances. People used to take it as a laxative (not recommended today, as ingesting high amounts may cause cancer). Use gloves when handling this chemical, as your skin  can absorb it on contact. I’ll show you how:


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Turning Water into Ink

Sunday January 10, 2010

You can use this as real ink by using it BEFORE you combine them together like this: dip a toothpick into the first solution (sodium ferrocyanide solution) and with the tip write onto a sheet of paper.


While the writing is drying, dip a piece of paper towel int other solution (ferric ammonium sulfate solution) and gently blot along where you wrote on the paper… and the color appears as blue ink. You can make your secret message disappear by wiping a paper towel dipped in a sodium carbonate solution.


You can also grow purple, gold, and red crystals with these chemicals… we’ll show you how!


Materials:


  • sodium ferrocyanide
  • ferric ammonium sulfate
  • 2 test tubes
  • distilled water
  • goggles and gloves
  • water
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Hot Liquids and Cool Solids

Sunday January 10, 2010

Dissolving calcium chloride is highly exothermic, meaning that it gives off a lot of heat when mixed with water (the water can reach up to 140oF, so watch your hands!). The energy released comes from the bond energy of the calcium chloride atoms, and is actually electromagnetic energy.


When you combine the calcium chloride and sodium carbonate solutions, you form the new chemicals sodium chloride (table salt) and calcium carbonate. Both of these new chemicals are solids and “fall out” of the solution, or precipitate. If you find that there is still liquid in the final solution, you didn’t have quite a saturation solution of one (or both) initial solutions.


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Elephant Toothpaste

Sunday January 10, 2010

I mixed up two different liquids (potassium iodide and a very strong solution of hydrogen peroxide) to get a foamy result at a live workshop I did recently. See what you think!


Note: because of the toxic nature of this experiment, it’s best to leave this one to the experts.



Nurses will put hydrogen peroxide on a cut to kill germs. It’s also used in rocket fuel as an oxidizer. The hydrogen peroxide in your grocery store is a weak 3% solution. The hydrogen peroxide used here is 10X stronger than the grocery store variety. The KI (potassium iodide) is the catalyst in the experiment which speeds up the decomposition of the hydrogen peroxide. This is an exothermic reaction (gives off heat).


What is Fire?

Sunday January 10, 2010

What state of matter is fire? Is it a liquid? I get that question a LOT, so let me clarify. The ancient scientists (Greek, Chinese… you name it) thought fire was a fundamental element. Earth, Air Water, and Fire (sometimes Space was added, and the Chinese actually omitted Air and substituted Wood and Metal instead) were thought to be the basic building blocks of everything, and named it an element. And it’s not a bad start, especially if you don’t have a microscope or access to the internet.


Today’s definition of an element comes from peeking inside the nucleus of an atom and counting up the protons. In a flame, there are lots of different molecules from NO, NO2, NO3, CO, CO2, O2, C… to name a few. So fire can’t be an element, because it’s made up of other elements. So, what is it?


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Decomposing Hydrogen Peroxide

Sunday January 10, 2010

h2o2This experiment below is for advanced students. If you’ve ever wondered why hydrogen peroxide comes in dark bottles, it’s because the liquid reacts with sunlight to decompose from H2O2 (hydrogen peroxide) into H2O (water) and O2 (oxygen). If you uncap the bottle and wait long enough, you’ll eventually get a container of water (although this takes a LOOONG time to get all of the H2O2 transformed.)


Here’s a way to speed up the process and decompose it right before your eyes. For younger kids, you can modify this advanced-level experiment so it doesn’t involve flames. Here’s what you do:


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Taking the Salt out of the Ocean

Sunday January 10, 2010

This experiment is for advanced students.Have you ever taken a gulp of the ocean? Seawater can be extremely salty! There are large quantities of salt dissolved into the water as it rolled across the land and into the sea. Drinking ocean water will actually make you thirstier (think of eating a lot of pretzels). So what can you do if you’re deserted on an island with only your chemistry set?


Let me show you how to take the salt out of water with this easy setup.


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Can Fish Drown?

Sunday January 10, 2010

If you’ve ever owned a fish tank, you know that you need a filter with a pump. Other than cleaning out the fish poop, why else do you need a filter? (Hint: think about a glass of water next to your bed. Does it taste different the next day?)


There are tiny air bubbles trapped inside the water, and you can see this when you boil a pot of water on the stove. The experimental setup shown in the video illustrates how a completely sealed tube of water can be heated… and then bubbles come out one end BEFORE the water reaches a boiling point. The tiny bubbles smoosh together to form a larger bubble, showing you that air is dissolved in the water.


Materials:


  • test tube clamp
  • test tube
  • lighter (with adult help)
  • alcohol burner or votive candle
  • right-angle glass tube inserted into a single-hole stopper
  • regular tap water
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Acids & Bases

Sunday January 10, 2010

If you had a choice between a glass of lemon juice or apple juice, most folks would pick the sweeter one – apple. Did you know that apples are loaded with malic acid, and are actually considered to be acidic? It’s just that there is so much more sugar in an apple than a lemon that your taste buds can be fooled. Here’s a scientific way (which is much more reliable) to tell how acidic something is.


Acids are sour tasting (like a lemon), bases are bitter (like unsweetened cocoa powder). Substances in the middle are more neutral, like water. Scientists use the pH (power of hydrogen, or potential hydrogen) scale to measure how acidic or basic something is. Hydrochloric acid registers at a 1, sodium hydroxide (drain cleaner) is a 14. Water is about a 7. pH levels tell you how acidic or alkaline (basic) something is, like dirt. If your soil is too acidic, your plants won’t attract enough hydrogen, and too alkaline attracts too many hydrogen ions. The right balance is usually somewhere in the middle (called ‘pH neutral’). Some plants change color depending on the level of acidity in the soil – hydrangeas turn pink in acidic soil and blue in alkaline soil.


There are many different kinds of acids: citric acid (in a lemon), tartaric acid (in white wine), malic acid (in apples), acetic acid (in vinegar), and phosphoric acid (in cola drinks). The battery acid in your car is a particularly nasty acid called sulfuric acid that will eat through your skin and bones. Hydrochloric acid is found in your stomach to help digest food, and nitric acid is used to make dyes in fabrics as well as fertilizer compounds.


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Fruit Battery

Sunday January 10, 2010

This experiment shows how a battery works using electrochemistry. The copper electrons are chemically reacting with the lemon juice, which is a weak acid, to form copper ions (cathode, or positive electrode) and bubbles of hydrogen.


These copper ions interact with the zinc electrode (negative electrode, or anode) to form zinc ions. The difference in electrical charge (potential) on these two plates causes a voltage.


Materials:


  • one zinc and copper strip
  • two alligator wires
  • digital multimeter
  • one fresh large lemon or other fruit
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Cobalt Colors

Sunday January 10, 2010

Cobalt chloride (CoCl2) has a dramatic color change when combined with water, making it a great water indicator. A concentrated solution of cobalt chloride is red at room temperature, blue when heated, and pale-to-clear when frozen. The cobalt chloride we’re using is actually cobalt chloride hexahydrate, which means that each CoCl2 molecule also has six water molecules (6H2O) stuck to it.


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Electroplating

Sunday January 10, 2010

If you don’t have equipment lying around for this experiment, wait until you complete Unit 10 (Electricity) and then come back to complete this experiment. It’s definitely worth it!


Electroplating was first figured out by Michael Faraday. The copper dissolves and shoots over to the key and gets stuck as a thin layer onto the metal key. During this process, hydrogen bubbles up and is released as a gas. People use this technique to add material to undersized parts, for place a protective layer of material on objects, to add aesthetic qualities to an object.


Materials:


  • one shiny metal key
  • 2 alligator clips
  • 9V battery clip
  • copper sulfate (MSDS)
  • one copper strip or shiny copper penny
  • one empty pickle jar
  • 9V battery
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Bread Chemistry

Sunday January 10, 2010

I have tried for years to make whole wheat bread from scratch, but my loaves usually wound up as hockey pucks or door stops. Although my house always smelled great, my family could never choke down the crumbs of my latest creation. That’s when I enrolled in a bread-making class. Guess what I found out?
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Iodine Rainbow

Sunday January 10, 2010

This is the experiment that your audience will remember from your chemistry magic show. Here’s what happens – you call up six ‘helpers’ and hand each a seemingly empty test tube. Into each test tube, pour a little of the main gold-colored solution, say a few magic words, and their test tubes turn clear, black, pink, gold, yellow, and white. With a flourish, ask them to all pour their solutions back into yours and the final solution turns from inky black to clear. Voila!


I first saw a similar experiment when I was a kid, and I remembered it all the way through college, where I asked my professor how I could duplicate the experiment on my own. I was told that the chemicals used in that particular experiment were way too dangerous, and no substitute experiment was possible, especially for the color reversal at the end. I was determined to figure out an alternative. After two weeks of nothing but chemistry and experiment testing, I finally nailed it – and the best part is, you have most of these chemicals at the grocery store. (And the best part is, I can share it with you as I’ve eliminated the nasty chemicals so you don’t have to worry about losing an eyeball or a finger.)


NOTE: This experiment requires adult help, as it uses chemicals that are toxic if randomly mixed together.  Follow the instructions carefully, and do not mix random chemicals together.


Are you ready to mix up your own rainbow?


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Chemical Matrix of Acids & Bases

Sunday January 10, 2010

If you love the idea of mixing up chemicals and dream of having your own mad science lab one day, this one is for you. You are going to mix up each solid with each liquid in a chemical matrix.


In a university class, one of the first things you learn in chemistry is the difference between physical and chemical changes. An example of a physical change happens when you change the shape of an object, like wadding up a piece of paper. If you light the paper wad on fire, you now have a chemical change. You are rearranging the atoms that used to be the molecules that made up the paper into other molecules, such as carbon monoxide, carbon dioxide, ash, and so forth.


How can you tell if you have a chemical change? If something changes color, gives off light (such as the light sticks used around Halloween), or absorbs heat (gets cold) or produces heat (gets warm), it’s a chemical change.


What about physical changes? Some examples of physical changes include tearing cloth, rolling dough, stretching rubber bands, eating a banana, or blowing bubbles.


About this experiment: Your solutions will turn red, orange, yellow, green, blue, purple, hot, cold, bubbling, foaming, rock hard, oozy, and slimy, and they’ll crystallize and gel — depending on what you put in and how much!


This is the one set of chemicals that you can mix together without worrying about any lethal gases.  I do recommend doing this OUTSIDE, as the alcohol and peroxide vapors can irritate you. Always have goggles on and gloves on your hands, and a hose handy in case of spills. Although these chemicals are not harmful to your skin, they can cause your skin to dry out and itch. Wear gloves (latex or similar) and eye protection (safety goggles), and if you’re not sure about an experiment or chemical, just don’t do it. (Skip the peroxide and cold pack if you have small kids.)


Materials:
• sodium tetraborate (borax, a laundry whitener)
• sodium bicarbonate (baking soda)
• sodium carbonate (washing soda)
• calcium chloride (also known as “DriEz” or “Ice Melt”)
• ammonium nitrate (single-use disposable cold pack)
• isopropyl rubbing alcohol
• hydrogen peroxide
• acetic acid (distilled white vinegar)
• water
• liquid dish soap (add to water)
• muffin tin or disposable cups
• popsicle sticks for stirring and mixing
• tablecloths (one for the table, another for the floor)
• head of red cabbage (indicator)


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What happens to helium when you chill it?

Sunday January 10, 2010

When you chill helium, nothing changes until it gets extremely cold. It remains a gas until it reaches a temperature below 5 Kelvin (-267.960 Celsius, -450.3280 Fahrenheit) at a pressure of 2.24 atm (227kPa).


1908 Heike Onnes cooled helium to below 5 Kelvin. At this temperature helium turns into a liquid. He could not solidify it by cooling it further because helium does not have a triple point temperature where solid, liquid, and gas phases are in equilibrium with one another. In 1906, solid helium was created by subjecting helium to a pressure of 25 atmospheres at a temperature below 1K.


At temperatures close to absolute zero, helium does not exhibit any viscosity. This makes helium, under those conditions, something called a superfluid.


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Iodine Clock Reaction

Sunday January 10, 2010

First discovered in 1886 by Hans Heinrich Landolt, the iodine clock reaction is one of the best classical chemical kinetics experiments. Here’s what to expect:  Two clear solutions are mixed. At first there is no visible reaction, but after a short time, the liquid suddenly turns dark blue.


Usually, this reaction uses a solution of hydrogen peroxide with sulfuric acid, but you can substitute a weaker (and safer) acid that works just as well:  acetic acid (distilled white vinegar). The second solution contains potassium iodide, sodium thiosulfate (crystals), and starch (we’re using a starch packing peanut, but you can also use plain old cornstarch). Combine one with the other to get the overall reaction, but note that there are actually two reactions happening simultaneously.


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What do I do with Ammonium Chloride?

Sunday January 10, 2010

So this is probably the last chemical in your set you haven’t used… I had to really dig into my ‘bag of tricks’ to find something suitable for you to practice with.


Ammonium chloride is found near volcanoes and coal mines, as glue for plywood, in hair shampoo, in the electronics industry in solder, and also is fed to cows. It’s not typically experimented with in the chemistry lab, but since it’s in your set, I thought we’d play with it and see if you can figure out a few of its properties.


Use gloves and goggles when handling ammonium chloride, and make sure you have a fire extinguisher and a grown up handy!


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Unit 8: Chemistry (Chemical Kinetics) Video

Sunday January 10, 2010

Why study chemistry? Baking is chemistry. Cars use chemistry to zip down the street. Your body converts food into energy using chemistry. Everything you see, touch, taste, and smell is a chemical.


Studying chemistry is like peeking under the hood of a racecar – you know you put gas in and it goes, but that’s all you can tell from the outside. Chemistry gets you into the inner workings on the molecular level. Are you ready? This video will get you started on the right foot for your study into chemical kinetics:


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Unit 8: Chemistry (Molecules) Video

Sunday January 10, 2010

Soon you’ll be able to explain everyday things, like why baking soda and vinegar bubble, why only certain chemicals grow crystals, what fire really is made of, how to transform copper into gold, and how to make cold light. Once you wrap your head around these basic chemistry ideas (like acids, polymers, and kinetics), you can make better choices about the products you use everyday like pain relievers, cold compresses, and getting a loaf of bread to rise. Are your ready? This video will get you started with your lesson in molecules:


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Rusty Balloon

Friday January 1, 2010

Mars is coated with iron oxide, which not only covers the surface but is also present in the rocks made by the volcanoes on Mars.


Today you get to perform a chemistry experiment that investigates the different kinds of rust and shows that given the right conditions, anything containing iron will eventually break down and corrode. When iron rusts, it’s actually going through a chemical reaction: Steel (iron) + Water (oxygen) + Air (oxygen) = Rust
Materials


  • Four empty water bottles
  • Four balloons
  • Water
  • Steel wool
  • Vinegar
  • Water
  • Salt
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Dinosaur Toothpaste

Friday January 1, 2010

Hydrogen peroxide is used to fuel rockets, airplanes, and other vehicle engines. Chemistry teachers everywhere use it to demonstrate the power of a catalyst.

To speed up a reaction without altering the chemistry of the reaction involves adding a catalyst. A catalyst changes the rate of reaction but doesn’t get involved in the overall chemical changes.

For example, leaving a bottle of hydrogen peroxide outside in the sunlight will cause the hydrogen peroxide to decompose. However, this process takes a long time, and if you don’t want to wait, you can simply toss in a lump of charcoal to speed things along.

The carbon is a catalyst in the reaction, and the overall effect is that instead of taking two months to generate a balloon full of oxygen, it now only takes five minutes. The amount of charcoal you have at the end of the reaction is exactly the same as before it started.

A catalyst can also slow down a reaction. A catalytic promoter increases the activity, and a catalytic poison (also known as a negative catalyst, or inhibitor) decreases the activity of a reaction. Catalysts offer a different way for the reactants to become products, and sometimes this means the catalyst reacts during the chemical reaction to form intermediates. Since the catalyst is completely regenerated before the reaction is finished, it’s considered ‘not used’ in the overall reaction.

In this experiment, you'll see that there's a lot of oxygen hiding inside the peroxide - enough to really make things interesting and move around! You'll also find out what happens to soap when you bubble oxygen through it. Are you ready?

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Electrolysis

Saturday October 10, 2009

This experiment is just for advanced students. If you guessed that this has to do with electricity and chemistry, you’re right! But you might wonder how they work together. Back in 1800, William Nicholson and Johann Ritter were the first ones to split water into hydrogen and oxygen using electrolysis. (Soon afterward, Ritter went on to figure out electroplating.) They added energy in the form of an electric current into a cup of water and captured the bubbles forming into two separate cups, one for hydrogen and other for oxygen.

This experiment is not an easy one, so feel free to skip it if you need to. You don’t need to do this to get the concepts of this lesson but it’s such a neat and classical experiment (my students love it) so you can give it a try if you want to. The reason I like this is because what you are really doing in this experiment is ripping molecules apart and then later crashing them back together.

Have fun and please follow the directions carefully. This could be dangerous if you’re not careful. The image shown here is using graphite from two pencils sharpened on both ends, but the instructions below use wire.  Feel free to try both to see which types of electrodes provide the best results.

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