Holiday How-to: Chocolate Leaves

My mom was a chemistry and home-ec teacher, so I grew up in a home where ingredients were carefully measured and food items were attractively arranged. While I got to help out in the kitchen as much as I wanted, I always liked being in the kitchen around the holidays. There were always new tricks or special touches added to dishes and along with these came short science lessons on why we were doing things that particular way.

One of my favorite things to help with in the kitchen were chocolate leaves. When done correctly, these are perfect little molds of the living leaf, just like the perfect molds and casts in the Morian Hall of Paleontology.

A chocolate leaf is made by smearing melted chocolate onto a leaf and putting it into the fridge to harden. Sounds easy, right? It is pretty easy. Read on!


Activity: Chocolate Leaves


Leaves (*See note in step 1.)

Chocolate candy melts

Parchment or wax paper

A cookie sheet or plate for your leaves to rest on as they cool


1. Pick your leaves. I like to use slightly waxy leaves so you don’t have to worry about fuzzy bits in your chocolate. NOTE: Learn about the plant you are picking leaves from before you decide to use them. Many household plants are decorative but poisonous.  Oleander is a great example of a plant that is pretty but poisonous. If you hate botany or don’t know about the Internet, getting pre-packaged basil or mint from the grocery store is a safe way to go. These leaves will be a little less firm, so you will need to be more careful with them.

2. Don’t pick leaves from poisonous plants. Seriously.

3. Wash your leaves with soap and water, rinse them thoroughly and then dry them completely. The chocolate won’t stick to wet leaves, so don’t rush this step. You will only be frustrated.

4. Put wax or parchment paper on a cookie sheet or plate. You want this to be something that will fit in the fridge with no problems.

5. Get out your candy melts. The melts come in a hundred colors. We are using chocolate colored ones in this tutorial. There will be instructions on the package on how to melt the specific brand of melts you purchased. In general, you will put the melts in a microwave safe bowl and microwave them a few seconds at a time stirring as you go. Don’t overheat the melts. They get gross and there is no coming back from that.

6. When you have everything melted and creamy, hold the leaf by its stem. I like pinching it between my thumb and index finger and then using my middle and ring finger to support the leaf. Do what feels comfortable to you.

7. Dip your stirring spoon into the chocolate. Use the BACK of the spoon to spread the chocolate on the leaf. Make sure the chocolate is thick enough that it won’t break when you try to peel it. Place the leaves on the parchment as you work, and don’t let them touch.


8. The side of the leaf you use is up to you. If you are using mint and you put the chocolate on the back of the leaf, you will have some crazy patterns.  If you want something more subtle, use the front of the leaf. Coat the leaf almost to the edges. If you go too far, you will get ugly edges that are hard to peel. But don’t worry! Those leaves are the best to eat.

9. Put the tray of leaves in the fridge and wait a few minutes.


10. When the chocolate is set, peel the leave off the chocolate. You should have a perfect little mold of your original leaf. This may take a little practice. Work quickly as you have something designed to melt with heat in your hot little hands.

11. Done! You can store the leaves in the fridge until you are ready to use them. If the leaves got soft when you were working with them, put them back in the fridge to firm them up. Once they are firm, you can toss them in a plastic container.


Okay! So what’s the science here?

The word “chocolate” comes from the Nahuatl word Xocolatl for “bitter water,” referring to its original incarnation as a hot, spiced beverage in the Mayan and Aztec traditions. Traditionally, chocolate is a mixture of cacao powder, cocoa butter, and a sweetener. To make chocolate palatable and stable, we now mix milk solids, added flavors, modifiers, and preservatives.

Those candy melts? NOT CHOCOLATE! In this example, they are sort of chocolate colored, so they have that going for them, but they also come in a bunch of colors that are not known to nature so… not chocolate. They are mostly made of sugar and vegetable fats – not cocoa butter – and depending on the brand, they may throw in a little wax for better melting. Mmmmm… wax.

The advantage to the melts over the regular chocolate is that they do have the wax and the vegetable oil in them, which makes melting easier since the chocolate doesn’t need to be tempered. It hardens pretty quickly and sticks to whatever you dip in it, so it makes a great coating for cake pops or whatever crazy things show up on Pinterest this month.

Want to get super nerdy about your chocolate?  (I assume you do…) MIT has these tidbits available.

What’s in typical chocolate?

  • 10-20% cacao
  • 8-16% milk solids
  • 32-60% sugar
  • 10-20% cocoa butter
  • 2% theobromine and polyphenols

Cocoa Butter Chemistry

Fats and oils are organic molecules made up of three fatty acids chemically linked by an ester bond to glycerol. Fats are solid at room temperature, while oils are liquid.

Cocoa butter fats are made up predominantly by three major fatty acid molecules: Palmitic Acid, Stearic acid, and Oleic acid.

Oleic acid is unsaturated (has a double bond on its carbon chain), making it kinked and unable to pack well with other molecules. Because of this, a greater portion of oleic acid in the fat results in a lower melting temperature for the cocoa butter.

Chocolate makers can adjust the amounts of each fatty acid to produce a chocolate that melts only in the mouth, giving it a superior quality.

Tempering chocolate

The cocoa butter in chocolate can have several different crystal structures (three-dimensional patterns in which the fat molecules pack). There are six known chocolate crystal forms, or polymorphs. You can obtain each form by varying the fatty acid ratios and the temperature at which the chocolate is tempered (cooled).

Only a few of the polymorphs are considered good for gourmet chocolate because they give the right blend of snap (when you bite into the chocolate) and melting (when it warms up in your mouth). Melting is especially important because it controls how well the chocolate disperses and releases flavor onto your tongue.

Whether you will be constructing culinary masterpieces this fall or sitting back and enjoying the kitchen creations of others, we hope you have a happy holiday with you and yours!  (And when you’ve had a little too much togetherness, we will be open on Friday…)

Go ahead. Take your toddler to the museum!

by Victoria Smith

When my children were younger, and I was hip to the toddler scene, I would schedule play dates at all the usual places: I’d push the stroller to the park, load up the red wagon for the zoo, and slip Cheerios to fussy babies during story time at the library. The Houston Museum of Natural Science was also on the top of my list, and I was surprised other moms thought their kids were too young to appreciate it.


“Oh, no! He’s after us!”

The museum is fantastic for small kids! It’s got air conditioning, wide spaces to navigate, and if you have a two-year old who will only eat peanut butter sandwiches cut in squares, not triangles, you are welcome to bring your own food.

And of course, DINOSAURS! They’re huge, they’re exciting and they have pointy teeth (at least the carnivores do). Even if you don’t have a toddler who can identify every prehistoric creature and pronounce the names better than most college graduates, every kid loves dinosaurs. (Thank you, Dr. Scott the Paleontologist!) In the Morian Hall of Paleontology, the dinosaurs are mounted in active poses, bringing these ancient creatures to life for young visitors. The displays tell a story, and the murals illustrate it.


It’s the Circle of Life, baby.

Speaking of stories, my youngest daughter’s favorite story is the lion chasing the zebra in the Hall of African Wildlife.  Even though she knows how it’s going to end for that poor zebra, every time she asks, “Mommy, tell me the story of the lion and the zebra.” It’s not only a great chance throw in a few Mufasa quotes, but it’s also great to discuss how nature doesn’t waste anything because after the predators come the scavengers. I usually manage to work in a moral lesson about the selfish leopard who won’t share, too. There are interdisciplinary opportunities at every turn!


Let me know when the wonderment is over, so Momma can sit down!

The Cockrell Butterfly Center is one of our favorite spots to visit, and perhaps even my favorite place in the museum, period. Yes, the awe and delight in a young child’s face is a daily miracle, but they’ve got cushioned benches and free wi-fi! When you’re through with the center, there’s a beehive-themed play area with puzzles and blocks, and most importantly, it’s enclosed!


My daughter at age four, as an assistant in a chemistry demonstration…

If you want your daughters (and sons, of course) to grow up to interested in science, it’s never too early to start. Let them know that science is fun and not scary. The museum has dedicated tour guides who specialize in making the exhibits come alive for young children, and docents who offer many hands-on experiences. Kids can touch real fossils, feel if minerals are rough or smooth, and guess if an animal was an herbivore or carnivore while holding an actual tooth! It’s all there, at their eye-level.  


…and at age eight, taking on a brain dissection at Xplorations summer camp.

So now that the big kids are back in school, it’s a great time to plan a visit to the museum. If you’re lucky like me, you can convince their grandparents that even though your one-year-old can’t talk, he really wants a membership for his birthday, and not another toy to clutter the playroom.

Editor’s note: Victoria is the Executive Assistant to the President of the Houston Museum of Natural Science.

Einstein Scavenger Hunt: Guess That Hall!

Editor’s note: This post was created by HMNS Concierge and Discovery Guide Corey Green.

Einstein at HMNS


Our good friend Einstein came to visit the museum and went through many of our exhibit halls. Can you name the halls he’s pictured in? (Click the pictures for answers!)

Einstein at HMNS Einstein at HMNS Einstein at HMNS Einstein at HMNS Einstein at HMNS Einstein at HMNS Einstein at HMNS Einstein at HMNS

 Want to go on a scavenger hunt with your very own Einstein? Good news! You can get him at the Museum Store!



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!