Posts in Category: investigations
popping popcorn
In a typical class or Friday night, I’ll pop popcorn and wonder: What happens to the stuff of the popcorn kernel as it is transformed into the morsel of popped corn that I can eat?
Those two “states” of the corn are really different. One I can eat easily, the other seems impossible and would break my teeth. So what happens to that stuff as it’s heated? In particular, does the stuff that’s there stay the same or does it change? I know that it’s different in some way, but how do I model the matter of this popcorn and where it goes (or stays)?
There are probably lots of great models and lots of great ways to think about this. As you do, you could use your model to predict if the kernel changes its mass as it is popped, or does it stay the same? And, if it does change, does it get more or less massive? And, regardless of what happens, what does that tell us? How do our models help explain what’s going on as popcorn is popped?
I documented this mini-investigation in a video:
Full video of my popcorn investigation.
I’m adding some space here so that there aren’t any spoilers. Below are a few screen grabs of the video that capture some key moments in my science and acting career.
Pointing out the kernel. It’s hard to see, because it’s small. That’s actually part of the challenge.
I thought I could weigh a single kernel to compare to after it popped. It’s really hopeless because the kernel is too small, and …
…wouldn’t it be a better idea anyway to have a bunch of kernels, in case some don’t pop or something else weird happens. Plus, this is easier to weigh.
The bucket by itself was 95 grams, but with the added kernels the total mass was 166 grams. So that means that the kernels by themselves were 71 grams, but it’s easy to just keep track of the popcorn in the bucket since that stays the same.
Live action! Pouring kernels into the air popper! (It’s probably important that I was using an air popper without any butter or oil.)
Popcorn! In the video, I speed up this part of the footage, which is kind of fun and convenient.
[Drumroll, suspense, etc.]
Final massing of the popped popcorn with the bucket. What happened?
A summary of our data.
Huh.
That’s a loss of a few grams. Doesn’t seem like much, but it’s pretty substantial in comparison to what we started with–about a 10% loss of stuff. So where did that go? It could be mistake, but this was monitored and it’s repeatable. We also talked about it being air in the kernels, or some kind of chemical reaction, or some loss of liquid water that could have been in the kernels. Or maybe something else.
There are a few things that could be helpful to know. For example, the density of air is something like 0.001 gram per cubic centimeter; and the density of water is about 1 gram per cubic centimeter. That helps us think about how much stuff we could lose of either of these and what we might expect that to look like.
This quick investigation was done with an air popper, but when I pop popcorn at home I do it over a stove and have a glass lid. This way I can see a little bit more of what’s going on. So, the other thing I could contribute is what it looks like when I pop popcorn. I recorded the video and put it on the internet, because I figured that was what the world needed:
Here’s few highlights from the video, just for posterity:
motion analysis: freefall
Adam went to the trouble of throwing a ball up into the air in his office. The ball not only went up; it came back down. Here’s video of the event:
(It’s also available on YouTube, here.)
You can study this motion in a variety of ways. In another video example, I suggest that you analyze the frames while using some kind of timing device. That could work here, especially if you can advance the video one frame at a time. Another way of doing this is with some video tracking software, such as JS Track, available online as a web based application. To use this, do the following, OR take a look at this video I made showing you the steps I use.
- Download the video that I’ve provided above; or, you can record your own!
- In JS Track, you’ll be prompted to upload the video file there. It’s best if the video is in mp4 format. That’s pretty natural for a lot of videos you record, but sometimes you’ll want to find a way to convert it by doing a quick search on the internet.
- Within JS Track, you can advance the video one frame at a time, starting with the first frame that’s of interest. I usually start with when the ball first leaves my hand. Then, you can leave a mark or point on your object (the red ball, in this case), and then the program will advance the video one frame. If you keep repeating this, you can get a collection of points.
- JS Track will then provide you with a bunch of position and time data, just like we created with rolling motion in class. It has a spreadsheet you can use if you download a copy and edit it for your own use, either in Google Sheets or Excel or something similar.
There’s more to talk about, but that’s exactly what the point of this assignment could be!
noticings and wonderings of scientists blowing bubbles
I dropped by the offices of scientists around my building here at Weber State University and asked them to blow bubbles and tell me about the things they notice and wonder. At the same time, I recorded video of these episodes on my phone. Here’s a quick 10-minute compilation of the things they did, noticed, and wondered.
My guess is that the things you’ve observed and wondered are really similar to these scientists.
Special thanks to (in order of appearance):
- Dr. Kristin Rabosky, Department of Physics and Astronomy
- Dr. Bridget Hilbig, Department of Botany and Plant Ecology
- Dr. Brandon Burnett, Department of Chemistry and Biochemistry
- Dr. Elizabeth Balgord, Department of Earth and Environmental Sciences
- Dr. C. David Walters, Department of Mathematics
- (all at Weber State University, College of Science)
It’s no secret that I enjoy blowing bubbles and I’ve made good use of them in classes, workshops, and informal learning settings, as I describe here. In all of these, I’ve made the case that:
- Bubbles have way more to observe and question than you’d at first imagine. That’s true of most things. The more you look the more you realize there’s more to see, and you could spend a lifetime learning more.
- The things that these professional scientists see with their trained scientific eyes are usually the same kinds of things that teachers and kids see and wonder.
- These scientists look like real people because they are. They look like they are having fun, even if they aren’t always completely comfortable while I’m there asking them to try something new while I’m running the camera.
hair’s width
The width of a human hair is pretty small, so you probably don’t have a good way of measuring it directly. However, you can use other methods, and these are the same as how you might study materials and the arrangement of molecules that you can’t see directly. We use the diffraction of light around these small structures, and we end up measuring how the light interferes as it goes through our object.
In my case, I had to pluck one of my hairs from my head. I don’t normally pull out my own hair, but this is for physics and for my students. I affixed the hair at the opening of the laser:
When I turn the laser on, you can see that it goes through and around the hair:
Here are some details about my laser for those who may be doing this calculation along with me.
Normally, this green laser would make a very precise dot, as Gus the cat is observing here:
However, with the hair in the path of the coherent green light, a diffraction pattern was formed. I lined things up so that the hair was running horizontally across the aperture of the laser, making the diffraction pattern align vertically. The staircase made a good place to set this all up, and one of my favorite books was a good prop for lining up the laser so that the pattern could be displayed on the wall above the stairs.
The diffraction pattern on the wall was in a good place for me to look at and measure it closely:
The central maximum is at the 50cm mark on this meter stick, with minima extending on either side. The projection of this pattern is 360 cm away from the aperture of the laser where the hair is taped. Here’s my schematic:
Based on all of this, how can you calculate the width of my hair?
turkey cooking times
Over the last few years, I’ve asked students and friends to send me their turkey cooking data. In particular, I ask for the time and temperature of the cooking, along with the weight of the turkey. I also add a place for extra notes, like how the turkey was prepared, if it was cooked in something besides an oven (e.g., a deep fryer or smoker), if it was stuff, covered, or otherwise modified.
This is imperfect, because everyone has all kinds of variations and conditions and measurement imperfections. But here’s a collection of data, mostly from 2020, but also from a few years past:
I’ll explain some details:
- I used most of the data I was given. Some submissions had numbers that were in the wrong units or just typos. I didn’t rule out too much, but if there was something that approximated the surface temperature of the sun or would have taken 4 years or would have killed an entire family, I discarded it. There weren’t too many in this camp, though. Fortunately. There probably are still some errors in here, because, well: science, meet real world conditions. 5th graders deal with this in science fair, so we might as well be brave enough to face it here.
- There are different methods of cooking all mixed together, and the people who used stuffing are mixed in with the non-stuffing people. That definitely causes scatter. But as I stare at this I think it’s less of an issue than I’d thought at first. It helps to have a lot of data.
- And there are different cooking temperatures. I highlighted the low temperatures (under 300 degress F) as blue, and the high temperatures (400+ degrees F) as red. And you see where they generally fall: red dots, with more thermal energy around the turkey, take less time than the general trend, and the blue dots, with less energy around the turkey, take more time than the trend.
- Most important, in spite of all all those weirdities, you can see there’s a definite trend: Bigger turkeys take longer to cook, but not in a linear fashion. My friend and very good physicist, Colin Inglefield, gave an entire physics seminar on this very thing several years ago, and now I have empirical data to help him out. If you’re interested, the Exploratorium walks through a nice explanation of this non-linear relationship, here:
https://www.exploratorium.edu/food/perfect-turkey
Thanks to all of you who contributed data and/or asked others to submit data. I’ll continue to do this and potentially update this page as results pour in each year.
drinking bird
I often host a lab where we study the Drinking Bird in its native habitat. But, in case you don’t have a chance to be in my lab and you don’t have your own drinking bird, here’s some video you can analyze. The bird goes through two of its cycles in this clip, and I repeat those cycles at high speed so you can see things in a different way.
A drinking bird is very simple, which makes its actions that much more interesting, I think. What do you notice? What do you wonder about? Can you trace out cause-and-effect rules in the bird and its motion? Can you create a model for how it’s working? In particular, how can something just move (and there are a few different motions in this bird) when it isn’t hooked up to anything else?
Appendix:
In case you need more footage of the drinking bird for longer amounts of time, I have about an hour and 15 minutes of video, both in real time and at 10x speed:
liquid motion
What makes up matter? We can’t see it directly, but observing some details might help us imagine what’s going on at a deeper level.
I have two glass bottles of water that I drop red dye into. All the water came out of my faucet, but the two bottles behave differently. What do you notice? What do you think might be happening? How do you picture or model the water and dye interacting? How could you investigate this on your own? What would you try?
sound tubes
Different musical instruments work because they play the note you want to hear. This seems obvious, but it’s no small thing to make something play exactly the right note, and leave out all of the other noise. How do they do this?
Instruments are made from lots of different stuffs and geometries. Some things, like violins and guitars, use tight strings to create their notes. Tuning forks and the reeds of a harmonica use vibrations of solid materials with specific lengths. Other instruments, such as organs and clarinets, produce the notes in a tube of air. That’s the kind of instrument I’m playing with here, except my tube is a simple piece of pipe.
You might not have a tuning fork to create this phenomenon, but is there something else you could do to make a tube sing? What other instruments could you create? What do you think the sound waves in the tube look like?
upward liquids
A lot of people don’t believe me when I tell them this, but I truly don’t understand how water crawls up a paper towel or string or piece of cloth. How does it get the energy to do this when it’s just sitting there; and the towel is also seemingly passive in the whole affair?
I’m a physicist and I work with many like-minded scientists. When I ask them about this phenomenon, they realize that it’s not all that simple, but probably it has something to do with electric forces in the towel and interactions with the water. I’m sure that this is part of the answer. But even so, I’m happy to admit that I don’t really understand it.
So, I assign the problem to my students and ask them to start to investigate different features of liquid absorption. They think of much better investigations than I would, and when we share these we start to come up with more ideas. To get them started, I’ve created this timelapse video of water moving up a cloth:
I thought my idea to speed up the video and include a clock in the frame was clever. I’m proud of that old-school technique.
What do you notice? What wonders strike you? What investigations could this spur? This is just the beginning.
Here’s what the scene looked like the following morning:
And then, later that morning, I detached the cloth and set the loose end on the table. It was originally dry, but then this puddle started to form:
Epilogue
In my classes, I see lots of really great examples of how this phenomenon can be turned into a research project with lots of different variables. Researchers create all sorts of different investigation designs with interesting variables and creative methods. This time-lapse video that Micah created gives a good impression of one of the hundreds of ways the climbing fluids can be studied, and it’s fun to see the process overviewed in just a couple minutes:
elevator physics
I like to send people into elevators with scales that they can stand on while traveling up and down. It’s a great exercise because they get to see some physics that they are actively a part of. At the same time, it becomes a nice conversation piece as different, surprised observers come in and out of the elevator we’ve turned into a laboratory.
I spent some time myself on the scale on an elevator, and I made a point of recording a round trip from the bottom floor to the top and back again.
I think it’s really important for you to know that this scale, like many, is a little sticky and is probably only trustworthy within a pound or so. That is, I think anything that between 158 to 162 pounds is really the same. Keep that in mind as you watch.
You can watch the video as many times as you’d like and look for connections between the motions of the elevator and the readings on the scale. What patterns do you see? What do you think the cause and effect relationships are? In other words, what makes the scale reading change; and what does not cause the scale to change from its normal reading?
This might inspire other experiments you can do on elevators. Does it matter if the person is bigger or smaller? If the elevator is faster or slower? What if you were on a roller coaster or other ride that might move you in more drastic ways? Can you model how the pushes and pulls on the rider would change?
Epilogue:
I made a new video, this one without captions but a smoother responding scale. I think it could be useful for another round of observations, or even as a place to start: