Ever wonder how fireworks… work wonders?

The Fourth of July just isn’t the same without pyrotechnics. And while the inevitable giant fireball from Dad lighting up the grill may be exciting in the moment, I’m actually referring to the giant chemistry demonstration we watch at night.


Fireworks are basically a bunch of combustion reactions, which are rapid chemical reactions involving oxygen gas (O2) combining with another substance. These combustion reactions are exothermic, which means energy is released during the reaction in the form of heat, light, and sound.

A firecracker explosion is essentially one large combustion reaction involving black powder or gunpowder, which is made up of potassium nitrate (KNO3), charcoal, and sulfur. Potassium nitrate will provide oxygen to the reaction, while charcoal and sulfur will act as fuel. This reaction produces a lot of gas and heat in very little time, and all of that gas produced needs a place to go. When too much of it builds up in an enclosed space and the pressure becomes too great, you get an explosion.

The basic components of a firework are a fuse, tiny explosives called stars, and a burst charge that triggers the explosion. Precise timing is also helpful.


First, you need an entirely separate explosion to get the firecracker up into the air. Typically to get the whole package airborne, you need what’s called a mortar, a long tube that directs the firecracker onward and upward away from bystanders. This explosion needs to be very controlled so you don’t set off the second firecracker inside, yet strong enough to get the whole package off the ground. A malfunction can have disastrous consequences. You can search for “fireworks fails” on YouTube for some disaster action.

When you light a firework, it’s not just one fuse; it’s two: the fuse that sends the firework up, and a time-delay fuse that is longer and burns more slowly, allowing the firecracker to gain some altitude before the second reaction begins. If the fuse is too short and the firecracker doesn’t fly high enough before exploding, it can get noisy (not to mention dangerous.)


Once the time-delay fuse expires, the stars begin to explode. A burst charge will explode and expel the stars, spreading them out. The stars themselves may have different chemical components within, but the basic idea is still a combustion reaction. There is some sort of fuel reacting with oxygen and producing a lot of gas and heat.


All those colors you see come from burning metals, which produce different wavelengths of light when heated. I don’t know how many of you have tried to burn metal before, but I can tell you from experience, it’s not easy.

We model this particular combustion reaction in one of our ConocoPhillips Science On Stage Outreach programs! Since lighting a firecracker in a school is a terrible idea, in Cool Chemistry, we use a fuel and some granular chloride salts in a beaker. When I light the fuel, I am beginning a combustion reaction that releases a lot of heat and will burn the metal salts.


The red/pink flame is from the metal lithium, sometimes used in batteries. You’ll notice that in this photo, there is a large Nalgene beaker covering the beaker that used to be full of green flames. That Nalgene beaker is airtight and cuts off the flow of air in and out of the beaker. When this happens, no new oxygen is allowed to enter; once the combustion reaction has used all of the oxygen inside the beaker, the flame will be put out.

Our beaker simulation doesn’t produce the loud bang we often associate with fireworks because it is open to the air around it. The boom heard is actually all of the gas building up inside of the firecracker being expelled all at once, moving faster than the speed of sound, just like the pop heard when a balloon bursts.

One prevalent legend says fireworks were invented accidentally by a Chinese cook some 2,000 years ago, and the basic concept has remained the same over the years. If anything, precise timing of explosions in fireworks shows has made the spectacle all the more enjoyable.

So grab some apple pie, pull out a lawn chair, relax and enjoy the world’s most famous combustion reaction, celebrating America’s birthday in style!

Bring the wonders of the Houston Museum of Natural Science straight to you with HMNS Outreach! To book a presentation of Cool Chemistry, email outreach@hmns.org or call (713) 639-4758!

Educator How-To: Crystals, Geometry and Chemistry

Math is beautiful and inescapable. Especially in nature, patterns and equations just keep showing up.  The path of an orbiting planet, the growth of a nautilus, arrangements of leaves on a stem, the efficient packing of a honeycomb; we can find rules and algorithms and make predictions from them.

Crystals, with their obediently repeating structure, are an elegant manifestation of the ‘rules.’  To be a crystal, your building blocks (atoms, molecules, or ions) must follow patterns over and over and over and over and over.  Atoms, being predictable, simply do what their chemical properties and the conditions (temperature, pressure, etc.) indicate.  So what exactly does it take to go from a mess of elements and compounds to this example from the Crystals of India exhibit at HMNS Sugar Land?

If you’ve ever tried making rock candy from sugar water or ornaments from borax solution, then you have some idea what it entails: something dissolved that is capable of making crystals has to slowly come out of solution – usually the longer you give it, the bigger it can grow and the slower it grows, the more perfect the crystals.

Freezing water into ice also gives you crystals; they just don’t stick around and let you handle them conveniently at room temperature. Water and solutions in water aren’t the only way to get crystals; molten rock cooling (slowly) can also give crystals, but that’s a little tricky for home experimentation.

So time is your friend for crystal growth, pressure is a factor, and it needs to be easier for atoms to attach to the forming crystal than to stay in solution.  Having a solution that is saturated or supersaturated so it can barely hold all of the dissolved material helps. It also helps to have places for the crystals to start forming; a tiny ‘seed’ crystal or sometimes even just a rough spot on a surface can provide the nucleation sites to kick off crystal growth. Are there other ways crystals and the things we consider ‘gems’ can form? Yes!

For those of us with shorter attention spans, a cool way so see the process is with crystallizing hand warmers – a pouch holds a saturated solution of sodium acetate. When you flex a metal disk inside the pouch, you kick off a chain of crystallization and end up with solid material (and released heat energy).  Because the process is so fast in the hand warmer, the individual crystals are very small and jumbled up (polycrystalline); oriented in all different directions, and as a mass they are opaque (light is refracting all over the place) and relatively dull rather than shiny and smooth as slower-forming large crystal faces can be.  The structure of most metals is also polycrystalline, and things like plastic and glass (even the kinds misleadingly labeled “crystal!”) are amorphous.

The external crystal shapes we see are related to the internal structure – there are a lot of different ways atoms can pack together.

Practically, there will always be some disruption in a crystal structure, no matter how perfect it may appear, which allows for some very cool effects – crystals “twinning,” impurities that alter the color; the reason ruby and sapphire (both corundum crystals) appear different.

Crystals aren’t always pretty! Sometimes we want to prevent crystallization to avoid things like kidney stones, but crystals are useful for all kinds of things; optical equipment and lasers, X-ray crystallography to figure out structures of proteins (and once upon a time, DNA), and silicon chips used in electronic devices. 

Whether you prefer your crystals practical or decorative, they are amazing!

Can’t get enough crystals? Check out the Crystals of India exhibit at HMNS Sugar Land (free for members!)



STEM & GEMS: Chemical Engineer Stevie Showalter Talks Nerdy To Us

Editor’s Note: As part of our annual GEMS (Girls Exploring Math and Science) program, we conduct interviews with women who have pursued careers in science, technology, engineering, or math. This week, we’re featuring Stevie Showalter, ALLEX Program Participant for Air Liquide.

Nerd Alert

HMNS: How old were you when you first become interested in science/technology/engineering and/or math?
It was literally second grade when I first learned the word chemistry. Then I was hooked. I wanted to be a chemist until high school when my parents and teachers swayed me to chemical engineering.

HMNS: Was there a specific person or event that inspired you when you were younger?
I had two really awesome chemistry/science teachers and two really awesome math teachers that pushed me to do my best and learn as much as I could.

HMNS: What was your favorite project when you were in school?
I always LOVED science fair season! I didn’t do it in high school because it wasn’t offered, but in 8th grade I advanced to the regional level with my project. My project was the efficiencies of different light bulbs (incandescent, fluorescent, black light) by measuring the temperature they gave off.

HMNS: What is your current job? How does this relate to science/technology/engineering/math?
Currently I work as an engineer for Air Liquide in their rotational training program. My last rotation I worked at a primary production plant making liquid and gaseous nitrogen, oxygen, and argon by separating those elements from the air through cryogenic distillation. My rotation now is all about maintenance and reliability. I currently evaluate all the ‘mini’ plants (I guess you could say) that we have at customer sites to see how we can increase their productivity.

HMNS: What’s the best part of your job?
The fact that our product reaches soooooo many people. You may not know it, but our carbon dioxide is in Pepsi and Coke. Our oxygen is the supply at many hospitals. Our nitrogen helps make different products like tires, rubber, car seats, and so many other things!

HMNS: What do you like to do in your spare time?
Read, go on bike rides, try new things and travel!

HMNS: What advice would you give to girls interested in pursuing a STEM career?
Just keep going! It’s fun and exciting and so satisfying to see your math and science in action!

HMNS: Why do you think it’s important for girls to have access to an event like GEMS?
To encourage them to pursue their geeky interests! It’s ok to be a nerd sometimes! Nerds and geeks run the world! (It’s ok that I say this, because I’m quite a nerd/geek)


Chemistry Demonstrations: This Eureka Moment is brought to you by HMNS Volunteers

Editor’s note: Today’s post was written by Tom Szlucha, a volunteer docent here at the Museum.

“EUREKA!” In his excitement, Archimedes runs down the street, naked and dripping wet from his bath. In this legend, he makes a discovery as he immerses himself in the bathtub and notices the water rise. 

It is this observation that leads to the solution to a problem that had been bothering him for some time.The king needs to know if the crown recently delivered by the goldsmith is pure gold or some cheap alloy — and Archimedes has found a way to determine what the crown’s made of!

This example of scientific discovery is based on the very simple observation of the water being displaced as a mass is lowered into it. Archimedes is obviously very excited by his discovery (maybe a bit too excited).

The ConocoPhillips “Hands-On” Demonstration Lab in the new Welch Hall of Chemistry stimulates this same sense of scientific discovery in visitors to HMNS (no bathtub for us though). Chemistry docents conduct hands-on experiments in this lab — experiments that teach, inspire and, most of all, are fun.


Now, back to Archimedes…According to the legend, he has to determine if the density of the metal in the crown is pure gold or a cheap alloy of gold.

He develops a very simple experiment to see if a density difference exists between the crown and gold. He places the crown on one side of a balance beam. On the opposite side, he places gold until the scale is balanced.

Then, he lowers the apparatus into a tub of water. If the balance tips to one side because the materials exhibit different buoyancy, then there is a difference in density — which would mean that a gold alloy was used to make the crown.

The principles of density and buoyancy involved in the Archimedes experiment are included in many of our chemistry demonstrations. The demonstrations are given by a group of dedicated HMNS chemistry docents. They come from a variety of backgrounds: chemists, engineers, educators, college students, and others. They have the enjoyment of making these fun, simple, and safe demonstrations that teach and instill an interest in physical science. In return, they are rewarded for their time and effort by seeing children smile with excitement as they make their own “Eureka!” discoveries.

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Tom Szlucha using the “pass-through” to set up

The theater area for these demonstrations is new and improved, a literal “step up” from the work cart that used to be parked in the old Chemistry Hall on the first floor. Downstairs, the new theater has a raised stage with large worktables in front and behind the presenter, allowing for multiple experimental setups. There are pass-through cabinets behind the rear table that facilitate the movement of materials from the preparation and a storage room located behind the stage.

Tom Szlucha in the prep room

Tom Szlucha in the prep room

The audience is seated on rows of black, rubber-coated cubes under the illumination of air molecules hanging from the ceiling. These molecules are different colors, proportionally representing the mixture of nitrogen, oxygen, and trace gases in the Earth’s atmosphere. The suspended molecules make a perfect transition into experiments associated with gases. The demonstration area is enhanced with a well-tuned wireless sound system, making the presenter easily heard by the seated audience.

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There are a variety of experiments performed here, most using simple household materials. Almost every school kid knows how to make a “volcanic eruption” by mixing baking soda with vinegar. But did you know that this acid/base reaction is endothermic, meaning that it absorbs energy, thus creating a cooling effect? A product of this chemical reaction is carbon dioxide gas. Since carbon dioxide is denser (i.e., heavier) than air, it can be poured to extinguish a flame. This stunt can come off as a magic trick—there is no liquid involved as you pour the invisible gas and extinguish the candle flame. Other practical lessons are taught through simple experiments, answering questions such as why do we wash our hands with soap; how do scientists measure the strength of acids and bases; and what does a baby diaper have in common with Jell-O?

Chemistry docents have plenty of opportunities to interact with the audience by soliciting help with these experiments. Participants learn about material density when they make hard-boiled eggs float on salt water and sink in plain water. They help show that Diet Coke is less dense than regular Coke. But why? The explanation is somewhat shocking. The average twelve-ounce can of sugar-sweetened soda contains about forty grams of refined sugar. That’s about three heaping tablespoons of sugar!

Participants also make a rubber “Superball” out of white glue and a simple ingredient found in the laundry isle of the grocery store. This polymerization process utilizes the boron atom in Twenty Mule Team Borax to cross-link the chains of polymers found in casein-based white glue. This experiment helps to teach visitors about some of the characteristics of polymers.

Chemistry Superball

Audiences entertained at the ConocoPhillips Hands-On Chemistry Demonstration Lab range from large school groups to families and individuals spending the day at the museum. The demonstrator has to be somewhat flexible, modifying their routine for the audience that is present. Having multiple tables with large surfaces allows for a number of different experiments to be set up and ready to go. Some experiments may be more suited to a particular age group, so the presenter can pick and choose, thus customizing each show to the specific audience.

If you are interested in joining in the fun by becoming an HMNS volunteer, please visit the HMNS web site to learn more or fill out the short registration form by clicking here.

The Volunteer Office will invite you to come to the museum for a short “get-acquainted” interview and will provide information about upcoming orientation programs. You don’t need to be an expert already, just interested in science! Our fun and comprehensive program will teach you everything you need to know to feel confident working with visitors and students in the HMNS exhibition halls. You’ll get to meet smart and interesting people, learn about a variety of scientific subjects, and become an integral part of one of the nation’s most-visited museums! We look forward to meeting you soon!