Kitchen Scientists Tackle the Chocolate Mug Cake

After an extended holiday absence, we're back with our Science Saturday experiments! We've been a little slow getting back into the swing of things. Our cold weather is adding to the lethargy...so we figured we'd try a nice WARM experiment today.

How about combining two of my very favorite things: science and chocolate? Where could we possibly go wrong with that? We did the first part in what will probably be a many part series on kitchen chemistry for kids: the science behind baking and cooking and food.

Today’s experiment focused on the role of proteins in baking. To do this, we made Chocolate Mug desserts. The Chocolate Mug Cake recipe includes an egg, and the brownie recipe does not. We were going to make both formulations and compare their textures. It was such fun to mix the chocolate batters and pour them into mugs, but seriously, people. We were doing some important scientific experimentation here.

When the Chocolate Mug Cake went into the microwave, the kids watched as it slowly puffed up and rose in an eerie column above the rim of the mug. That’s when we discussed the main points of our kitchen chemistry for kids.

“See our cake getting big and poufy?” I asked the kids. “That’s the gas bubbles getting hot and growing bigger, making the dough squish out. Then think about the eggs. Eggs are full of protein. When the protein is cooked, it changes the shape. [This is a process called denaturing.] The protein becomes kind of like beams in a building to hold up the cake. Then the flour is kind of like sheetrock or cement to go over the beams and complete the structure of the building. Without the strong proteins, a light and fluffy building wouldn’t be able to go quite so high."

I got nods of agreement, especially from Jayman who is fascinated by construction sites and seemed to understand about building beams and cement. Just for comparison, we made a Chocolate Mug Brownie, which doesn’t include an egg. We compared textures – the cake was spongy and airy while the brownie was very dense and squishy.

And, of course, the very best part of our kitchen chemistry for kids came last. We got to eat the lovely chocolatey experiments we’d concocted. They were both pretty yummy, although the cake was better than the brownie, in our opinion! I need to do a little more tinkering with the recipes to get them just right. 

I’m thinking if there were a few more units like this in high school chemistry, we’d have a lot more scientists running around! It was a very delicious day of kitchen chemistry for kids. 

Just as a side note: If you try this at home with your kids, don’t expect the final result to be exactly like a cake or brownie you’d bake in the oven. The texture of both products is somewhat different—but it’s instant gratification for a sudden chocolate craving. Not bad for a humble mug.

Chocolate mug cake:

¼ cup flour

¼ cup sugar

2 Tbsp. cocoa powder

2 Tbsp. beaten egg

3 Tbsp. milk

3 Tbsp. vegetable oil (you might also try a mixture of oil and applesauce, for a lower-fat result)

3 Tbsp chocolate chips

Mix everything and place batter into a large mug that has been sprayed with cooking spray. Microwave on high for 1 minute, then check with a toothpick. Cook in intervals of 2

0 seconds until done. If you leave the cake just slightly underbaked (where a toothpick comes out a little goopy), it will continue baking as it cools. Don’t overbake or it will be tough! Allow cake to cool for several minutes in the mug, then turn out onto a plate. Enjoy immediately!

Chocolate mug brownie:

¼ cup flour

¼ cup sugar

2 Tbsp. cocoa powder

2 Tbsp. vegetable oil

4 tsp. water

3 Tbsp chocolate chips, if desired

Assemble and mix as above, pouring batter into a sprayed mug. Microwave on high for 1 minute then check. Cook in intervals of 15 seconds until done, if necessary. Brownie will lose its shininess and exhibit cracks in the top when done. Allow to cool slightly and enjoy.

Christmas Crystals

This project was actually a week in the making. You see, I was teaching kids about crystals. They take a while to grow, so we’ve been watching this experiment all week long and talking about our observations. But the result – beautiful Christmassy rock candy – is worth waiting for.

To begin, I asked Jay to build a cube out of his snap-together blocks. He quickly obliged.

“Today we’re going to pretend that these blocks are a crystal. A crystal is a bunch of atoms or molecules joined together to make a solid cube. It looks like these blocks,” I told the kids.

I put a few sugar crystals in my hand and showed the kids. “Can you look very closely at these tiny crystals? They’re shiny and hard and kinda square or rectangular.” The kids examined and touched the sugar crystals for a while.

Next, we put 1 cup of water into a pot and put it on a hot stove. We added a cup of sugar to the water. The kids watched as the sugar crystals dissolved into the water. “When we put the sugar into the water, the crystals break up,” I told the kids. We broke apart Jay’s blocks that had made a cube.

Then I asked Jay to rebuild his block cube. He took a block in one hand and started to connect it to another block. “Stop!” I said. “See that single block you’re holding in your hand? That’s what you need to start building your crystal, right? The same thing will happen with the sugar. Now that we’ve broken apart the crystals, they need something to help put them back together. They need what’s called a “seed” that they can grow from.”

We took a short dowel, dipped it into the sugar water and then rolled it in more granulated sugar. Those crystals will be the seeds from which the rock candy crystals will grow. We set that aside to dry.

Next, we added two more cups of sugar to our sugar mixture – three cups total to one cup of water. We stirred after each cup was added until the solution became clear again. Heating the solution gently helps the sugar crystals break apart and go into solution. But don’t boil the solution for more than a minute if necessary – it will start to turn into hard candy.

Finally, we had a saturated solution. That means we’d dissolved as much sugar as the water could hold and it was starting to re-crystallize. We turned off the heat and set the sugar solution aside to cool for about 20 minutes. I added a few drops of food coloring and some essential oil flavorings. We made a batch of red cinnamon candy for my spicy Allie and a batch of green wintergreen candy for my smooth Jay and a batch of yellow lemon candy for Emmie.

Once the solution was cool and crystals were beginning to form on the surface, I poured the solution into clean pint-sized glass jars. We took our dowels that had been rolled in sugar and placed a clothespin horizontally across the stick about ¼ of the way up. The clothespin will rest on the lip of the jar and hold the stick upright in the sugar solution without letting it touch the sides or bottom of the jar.

The dowels went into the jar and we began our vigil. Slowly, over the course of a week, we watched the sugar crystals begin to form on our dowels. Every day or two, I’d pull the stick out and break up the crystals that had formed on the surface of the solution. Those crystals would sometimes stick to the dowel and make beautiful jagged peaks.

Finally, when the crystals have reached the desired size, we removed the dowel. I let it drip into the jar for a minute or two, then laid it on a paper towel to dry.

Voila! Beautiful Christmas rock candy and a fun science project all about crystals. The kids were fascinated to see these intricate, shiny stones appearing out of nowhere from a liquid solution! 

Glorious Goo and Polymers Too!

Our Science Saturday project today turned out to be one of my favorites so far: it was all about polymers.

Actually, this was one of my favorite units when I taught college chemistry, too. Polymers are awesome. I wanted to come up with some ideas to make polymers fun for kids.

We began our activity with simple pop blocks. You know those giant beads that pop together? I let the kids string beads together like giant trains. As my babies played, I was teaching kids science.

 

“Polymer means 'many parts,'” I told them. “Just like the blocks you’re putting together. Polymers are giant molecules with lots of pieces.”

I turned to Jay. “What kinds of pieces are on a train?”

He thought very seriously for a few seconds. “Well, there could be boxcars and flatcars and oil tankers and engines and cabooses.”

“Could you make lots of different trains with all those pieces? Maybe some that have ALL boxcars and some that have oil cars and flatcars?”

And just like that, our Polymers for Kids lesson took shape. The kids were envisioning polymers as giant trains with all sorts of different cars. Meanwhile, they were building long strings of beads to represent polymers. Some strings were all the same color, and some were rainbow colored.

Once we go the polymer strings built, we moved on to the experiment part. We were actually going to make and play with some real polymers.

For this part, we just needed cornstarch, water, and food coloring (which is optional). We mixed together about 2 cups of cornstarch and 1 cup of water. It made a bowl full of a substance that’s neither quite a liquid nor a solid—but some of both. The polymers that make up the cornstarch have some very fun properties.

If you jam your fingers into the bowl, it will feel like a solid wall. That’s because the long polymer strings are too large to move out of the way quickly. However, if you slowly lower your fingers into the bowl, it will feel like a thick liquid because the polymer chains shift away from your fingers.

It was wild. Even hubby and I were playing with our bowl of homemade polymer goo. We made a mess of epic proportions, but because it’s just cornstarch and water, it cleaned up quickly with a damp paper towel.

If you're looking for a simple activity that is wildly fun, super easy, and incredibly cheap, this is your pay dirt. And from the looks on my babies’ faces when they stuck their fingers into a bowl of crazy goop, they feel the same way.