Repost: Drooling Pumpkin Chemistry Lab for Halloween!

 

With Halloween just around the corner, I thought it was a good time to repost this description of a fun chemistry lab you might like to try.

In this Halloween chemistry lab, students create a jack-o-lantern that foams at the mouth! You can use the lab to address NGSS standard MS-PS1-2 as students observe properties of the reactant (hydrogen peroxide) and the bubbly products of the reaction.

I have used the "drooling pumpkin lab" with students in seventh and eighth grade. The class size has usually been about twenty-five students, and there has always been another adult in the room with me. This is helpful for managing materials and spills and to keep an eye on safety because sharp tools are required to carve the pumpkins. Students usually keep their behavior in check because they are excited to do the lab and know that safe behavior is a requirement for participation.

Students work at tables in pairs or small groups. They start by carving their pumpkin into a jack-o-lantern.

Before carving the pumpkins, be sure to put them onto a tray or paper to protect the tables because it gets messy! Suggest to students that positioning the jack-o-lantern's grin lower on the pumpkin will help the reactants flow out of its mouth. (After carving the pumpkins, you will have lots of seeds, so you could ask parents ahead of time if they would like to take some home to roast in the oven.) Depending on how much time you have with students, carving the pumpkins alone can take a full class period.

The reaction used to create the foam that oozes out of the jack-o-lantern's mouth is the decomposition of hydrogen peroxide, a liquid easily found in solution at pharmacies. Yeast is used as a catalyst in the reaction, so this is a good opportunity to teach students how a catalyst does not take part in the reaction but merely helps it happen. (I found a one-pound bag of yeast online and stored it in the freezer for many years.)

To activate the yeast, student groups mix a few tablespoons of yeast with a few tablespoons of lukewarm water in a small container and let it sit for about 5 minutes, forming a paste. Meanwhile, students pour about 1 cup of hydrogen peroxide solution into another small container and mix in a few drops of dish detergent. (I recommend using an unscented soap for students sensitive to smells.) The dish detergent will capture the bubbles produced by the decomposition of hydrogen peroxide, creating a foam.

Students lower the container of hydrogen peroxide solution with dish detergent into the jack-o-lantern, add the yeast paste, and stir. Soon, the reactants flow out of the pumpkin's mouth, causing it to drool! In some cases, positioning the container of hydrogen peroxide close to the jack-o-lantern's mouth can help students get this effect.

So, where did the bubbles come from? Yeast speeds up the decomposition of hydrogen peroxide into hydrogen and oxygen, and these gases are captured by the soap, creating the foam. Students can easily see that a chemical reaction has occurred!

If you are interested in other fun chemistry labs, you might like this blogpost on making "gel worms":

https://www.scientificcreative.com/2022/05/polymer-lab-gel-worms.html

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Valentine's Day Special: Sexual Selection and Widowbirds

 Photo by David Howard on Unsplash

Are you looking for a way to get the attention of your middle school science students? The funny topic of sexual selection can make for an entertaining lesson on Charles Darwin’s theory of natural selection. It certainly drives home the message that natural selection is all about reproductive fitness! 

You can use the concept of sexual selection to help teach Next Generation Science Standard (NGSS) MS-LS4-4: Construct an explanation based on evidence that describes how genetic variations of traits in a population increase some individuals’ probability of surviving and reproducing in a specific environment. Although you can cover sexual selection whenever you are learning about natural selection, it’s a fitting topic to teach right around Valentine’s Day.

Sometimes we see traits in nature that at first seem difficult to explain using the theory of natural selection and the concept of “survival of the fittest”. The traits don’t seem to serve any obvious purpose for helping the individual to survive. One example is the widowbird- aptly named, as you will see. The female looks normal enough, with brown, camouflaged coloring. The male widowbird, on the other hand, has an extraordinarily long tail. 

Photo by David Howard on Unsplash

How did that happen? Why would nature “select” a long, seemingly cumbersome tail like that? When I ask students what potential problems a long tail like that could cause, they have several ideas. The long tail might be heavy and make it hard for the bird to fly. A predator trying to catch the bird could grab it by the tail when it is trying to fly away. One student said that the tail looked “ugly”, but I guess that beauty is in the eye of the beholder…

One researcher who had a hunch about how natural selection could result in such extraordinarily long tail feathers decided to do a little experiment test his hypothesis. You and your students might question the ethics of this experiment, and it might seem like a bit of a mean trick, but what the researchers did was to clip tail feathers short on some birds and add them to the tails of other birds, making their tails ridiculously long. The male widowbirds were then followed to see how successful they were at winning over the females. Would you like to guess which male birds were most successful at attracting females? You've got it- the ones with the absurdly long tails! So, it was the ladies' fault- the females were selecting the tails!

This graph shows the success of the male widowbirds with and without altered tails:

Widowbird Graph

Using the graph, I ask students to answer these questions:

1. Approximately, what is the average number of active nests of widowbirds that had their tail shortened? 

2. Approximately, what is the average number of active nests for the birds that had their tails lengthened?

3. Approximately, what are the averages for the normal and control groups?

4. Do you see a correlation between tail length and the number of nests a male bird has?

5. Can you think of another explanation for this finding, aside from sexual selection, for longer tail feathers?

6. What might you conclude is a possible explanation for why the widowbird has evolved such long tail feathers?

This short BBC video clip from Planet Earth II, narrated by David Attenborogh, shows male widowbirds in action as they strut their stuff for females:

BBC Earth: Male Widowbird Display

The video gives a clue about the purpose that long tail serves: showing off for the females. Natural selection is about survival of the fittest, but fitness is really a measure of an individual's reproductive success. An individual with lots of offspring will pass on its traits to all of its babies. This is how a trait becomes more common in a population. In the case of sexual selection, there can be a snowball effect as females that prefer a certain trait, such as a longer tail, pass on this preference to female offspring, and male offspring inherit the trait. Over time, the trait can become more and more pronounced. Was there originally some benefit to having a slightly longer tail? Students often say that maybe it helped with balance in flying. There are different theories about how the whole thing got started.

The story of the long-tailed widowbird (aptly named?) can make for an entertaining Valentine's Day story to share with students.

For more information on the study of the widowbird's long tail, follow this link:

https://static.nsta.org/case_study_docs/case_studies/widowbirds.pdf

Sexual selection is not limited to birds. Here's a video that students like showing the display of a male peacock spider:

Peacock Spider Courtship Video

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It's Tide Pool Season in California!

 

As we get closer to winter, the low tides become especially low, so this is an excellent time for viewing ocean life in tide pools. It's a time of year I always look forward to! 

Tide pooling season begins in the fall and continues through the winter and into early spring. It is at these times when you can catch a negative tide during the daytime. If you want to plan a trip, it is helpful to first consult a tide chart like this one for San Diego:

Tide Chart for San Diego

A ranger at Cabrillo National Monument said that any tide at or below 0.7 feet is good for viewing sea life, and the lower the tide, the better.

A trip to the tide pools is always a favorite among students. It feels great to get out to the ocean, and there are always so many things to explore and discover.

California Sea Hare

California Sea Hare Eggs

Tide pooling is a nice activity to do with your family, too!

If you plan to explore to explore tide pools with a school group and live in the San Diego area, Cabrillo National Monument offers some great ranger-lead programs for K-12 students. Their programs are free, and many are aligned with the Next Generation Science Standards (NGSS). 

With middle school students, I have participated in the Science Sampler and the Climate Kids programs, both for grades 5 - 12. The Science Sampler program engages students in practicing data collection on populations of organisms living in tide pools, modeling the way in which biologists collect this data at Cabrillo National Monument. The Climate Kids program addresses the affects of climate change, specifically ocean acidification, on sea life. 

Another benefit of a ranger-lead experience is having an expert help you spot hard-to-find creatures such as nudibranchs, sea hares, and on rare occasions, an octopus.

Spanish Shawl Nudibranch

If you are interested in learning more about the science programs offered at Cabrillo National Monument, follow this link:

Cabrillo National Monument Science Programs

Whether you explore tide pools independently or with a ranger, here are some things you might like to have with you:

* Closed-toe shoes with good traction (old sneakers)

* Pants that can be rolled up and warm layers on your upper body

* Sun protection (hat, sunscreen)

* Towel(s)

* Change of socks, shoes, and clothing (just in case you slip in the water)

* A Ziplock bag for your cell phone, if you bring one (not advised for students)

When wading in the tide pools, keep your eyes out for big waves, and avoid turning your back to them. Walk between the rocks rather than stepping on them. If you step on rocks to avoid walking in the water, you could easily slip on algae and really get yourself wet!

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Why Do Leaves Change Color in the Fall?

 

Why do leaves change color in the fall? This is the question I posed to my ten-year-old daughter when we took a short trip to Maine this month. I gave her the assignment of doing some research on the topic and writing a response. When I read what she had written, I thought that she had done very well with her explanation. I told her that we should share it with others, who might enjoy learning from what she had written. She suggested I post it on my blog, so here it is! The following piece and the photo of foliage above were done by her.

The leaves change color in the fall because the leaves start producing less chlorophyll. If you are wondering, chlorophyll is a chemical that makes leaves green. Chlorophyll is responsible for photosynthesis, when plants take in water and carbon dioxide and use sunlight to make sugar to feed themselves. In the fall, there is less sunlight, which means less photosynthesis for the plants and less need for chlorophyll. When this happens, the trees prepare to go dormant in the winter. Without chlorophyll, the green leaves start turning into red, orange, yellow, and brown leaves. As the chlorophyll breaks down, the carotenoids, orange-yellow and brown pigments, and anthocyanin, red and purple pigments, are revealed and/or created. (Most anthocyanin is created in the fall.) That is why sometimes the leaves are not solid colors, but a mix of colors because the carotenoids and the anthocyanin are slowly being revealed and/or created while the chlorophyll breaks down.

I hope that you enjoyed reading my daughter's work and perhaps learned something, too!

If you are interested in other blogposts related to science topics we explored while on vacation, here are a couple of links:

Snow Science: Freezing and Melting Points the Same?!

Slime: Vacation Fun with Polymers!

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Drooling Pumpkin Chemistry Lab for Halloween

 

In this Halloween chemistry lab, students create a jack-o-lantern that foams at the mouth! You can use the lab to address NGSS standard MS-PS1-2 as students observe properties of the reactant (hydrogen peroxide) and the bubbly products of the reaction.

I have used the "drooling pumpkin lab" with students in seventh and eighth grade. The class size has usually been about twenty-five students, and there has always been another adult in the room with me. This is helpful for managing materials and spills and to keep an eye on safety because sharp tools are required to carve the pumpkins. Students usually keep their behavior in check because they are excited to do the lab and know that safe behavior is a requirement for participation.

Students work at tables in pairs or small groups. They start by carving their pumpkin into a jack-o-lantern.

Before carving the pumpkins, be sure to put them onto a tray or paper to protect the tables because it gets messy! Suggest to students that positioning the jack-o-lantern's grin lower on the pumpkin will help the reactants flow out of its mouth. (After carving the pumpkins, you will have lots of seeds, so you could ask parents ahead of time if they would like to take some home to roast in the oven.) Depending on how much time you have with students, carving the pumpkins alone can take a full class period.

The reaction used to create the foam that oozes out of the jack-o-lantern's mouth is the decomposition of hydrogen peroxide, a liquid easily found in solution at pharmacies. Yeast is used as a catalyst in the reaction, so this is a good opportunity to teach students how a catalyst does not take part in the reaction but merely helps it happen. (I found a one-pound bag of yeast online and stored it in the freezer for many years.)

To activate the yeast, student groups mix a few tablespoons of yeast with a few tablespoons of lukewarm water in a small container and let it sit for about 5 minutes, forming a paste. Meanwhile, students pour about 1 cup of hydrogen peroxide solution into another small container and mix in a few drops of dish detergent. (I recommend using an unscented soap for students sensitive to smells.) The dish detergent will capture the bubbles produced by the decomposition of hydrogen peroxide, creating a foam.

Students lower the container of hydrogen peroxide solution with dish detergent into the jack-o-lantern, add the yeast paste, and stir. Soon, the reactants flow out of the pumpkin's mouth, causing it to drool! In some cases, positioning the container of hydrogen peroxide close to the jack-o-lantern's mouth can help students get this effect.

So, where did the bubbles come from? Yeast speeds up the decomposition of hydrogen peroxide into hydrogen and oxygen, and these gases are captured by the soap, creating the foam. Students can easily see that a chemical reaction has occurred!

If you are interested in other fun chemistry labs, you might like this blogpost on making "gel worms":

https://www.scientificcreative.com/2022/05/polymer-lab-gel-worms.html

I hope that you found this blog post valuable. If you are interested in joining my email list, please follow this link:

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Snow Science: Freezing and Melting Points the Same?!

 Updated December 23, 2022

We were hoping for snow when we went to Maine over winter break. We were lucky to not only get snow, but sticky snow, which is perfect for making snowmen! (My daughter repeatedly reminds me that we actually made snowwomen!)

As the snow started to fall, the temperature was hovering around 32 degrees Fahrenheit, the freezing point of water. We tried to see snow crystals, or snowflakes, as they fell, but the crystals were partially melted and clumpy. The weather provided a natural lesson about changes of state- in this case, freezing and melting.

I shared with my daughter that the freezing and melting points of water are the same (technically, there are small observed differences). 

How is it possible that freezing and melting, which are opposites, happen at the same temperature?

This didn't make sense to her. I asked her whether water would be ice or liquid water just below the freezing/melting point. It would be ice! What about just above the freezing point? It would be liquid water! She realized that the freezing/melting point is the threshold between these two states of matter.

The snow we used for making our snowwoman and snowgirl had the perfect mix of solid and liquid water to create a sticky snow. We started with a small snowball and rolled it on the snow-covered ground. It grew very quickly!

We piled the giant snowballs on top of one another, and added some embellishments that we found around the yard.

We were lucky to have the sticky snow we hoped for on this trip. Maybe on a future trip, we will experience the fluffy powder snow that's perfect for sledding!

Here is a video from the Fleet Science Center that discusses simple snowflake science and gives directions for making six-pointed paper snowflakes. I used it with my middle school students for a relaxed activity just before winter break. I think it would also work well with grades 3 - 5.

Fleet2Go: How to Make Paper Snowflakes

I also used this video on snowflake science with my middle school students:

The Science of Snowflakes

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Caga Tió- The Catalan Christmas Pooping Log!

Updated December 23, 2022

Keeping students engaged in the days before Winter Vacation is quite a challenge for a teacher, but for Caga Tió, it's effortless! When I told my middle school students about Caga Tió and asked whether they would like to care for him in our classroom as part of Spanish class, they were all in! 

Early in my teaching career, I spent a year in Barcelona, where I taught English and lived with two Catalan roommates. My roommate Quim described a Christmas tradition of wrapping a log in a blanket to keep it warm, giving it food and water, and then, on Christmas morning, hitting it with a stick to make it "poop" turrón (almond candy). For a long time, I didn't believe him and thought he was trying to fool his American friend. One day, he insisted I come quickly to see what was on TV, and sure enough, there was a black-and-white video of children singing and beating a log with a stick. It was true!

The Caga Tió, or "poop log", I used in my classroom was one given to me by a friend. It's a simple little log with two sticks attached to look like legs and a face drawn on the front:

I wrapped it in a large throw blanket- large enough for hiding the nuts and turrón later on. Before we welcomed Caga Tió into our classroom at the beginning of December, my students assured me that they would take good care of Caga Tió by keeping it safe and warm, feeding it little pieces of food, and bringing it water. There were a few seventh graders who took on most of this- it was very sweet! 

We kept Caga Tió close to my classroom nook in a corner of the room that was visible yet a little less accessible in order to avoid any possible rough handling. My students asked if I had a little cup for water, and I found one in my science closet. Students filled the cup daily, and I gradually emptied it throughout the day when they weren't looking. I did the same with the food they left, which was mostly fruit.

On the last day of Spanish class before Winter Break, I taught students a simplified version of the Caga Tió song, one that my friend had taught me. The song is not in Spanish but in Catalan, a language spoken in the state of Catalonia. (You can find the traditional Caga Tió, or Tió de Nadal, song on Youtube) It was a good opportunity to tell students that Catalonia has its own distinct language and culture.

Before passing out sticks to my students, I reminded them that the sticks were, of course, not for sword fighting or hitting each other but for gently hitting Caga Tió. For Spanish class, I had a smaller class size of about 12 students, making this activity more manageable. Although my class sizes are usually around 25 students, during Spanish class, half the students are in P.E., while the other half is with me. 

Caga Tió was set on a desk, and students walked around him together in a circle, hitting him with their sticks and singing the Caga Tió song. Then they heated their sticks in a fire- made by my wonderful teaching assistant Nicole- before returning to hit Caga Tió and sing to him again.

When we thought students had sung enough for Caga Tió to work his magic, we lifted the blanket. It worked! He pooped!

  

I first offered almonds to students and then worked at cutting the turrón into pieces. (I have found turrón in the Little Italy neighborhood in my city of San Diego, and you can also buy it online.) There are two types of turrón- hard and soft. The hard turrón, or turrón duro, is difficult to cut into pieces but doable with a good knife. For students with allergies to almonds and/or eggs, I had alternative candies under the blanket marked with their names on sticky notes. 

Having Caga Tió in our classroom in December gave students something to look forward to in coming to school, and I had the chance to have a little fun with them!

If you would like to know more about Caga Tió, you can read this NPR article:

A Catalan Log That Poops Nougats At Christmas

This video includes the Caga Tió song and a description of the tradition:

Caga Tio or Tio de Nadal Comes to the United Kingdom

For any students out there who do not believe in Tió, here is video proof that he can eat and drink:

Tió menjant 

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