I always keep in mind when I teach that it’s great if kids make scientific discoveries during the course of a year. I have found that, usually, direct instruction is best, followed by hands-on activities and review. It’s difficult to discover something specific. It’s better for them to develop good questions and then to try and answer those questions on their own using guided instruction.
It is important to bear in mind that entire civilizations failed to discover the idea of zero as a place-holder for operations such as addition and division. If the Romans couldn’t develop an effective method of division over the course of eight centuries, it seems unrealistic to expect children to discover a great deal on their own.
I finished my solar panel project this week. I’ve been working on it on and off for the past two years and it’s finally done. The only thing I need to complete is to put the clear acrylic panel on top to protect the cells.
Here are my previous posts on building the solar panel. Part 1 gives information on the parts I bought to build the 18 volt, 60 watt PV solar panel. Part 2 describes my frustration of learning to solder the cells and the time needed to do this well. Part 3 describes my attempt to solder the tab wire to the negative part of the cell and how I’m going to wire the cells to produce the correct voltage. This last post will summarize the task of completing the solar panel before school starts and what my future plans are with solar power panels.
It took me a couple of days to complete all the soldering. I got better at it as I went along and only broke a few cells. Luckily I bought enough and I still have about ten left. The hardest part was dealing with corrosion that built up on the tip of the soldering pen and getting an even flow of solder to flow onto the three positive connections on the back of the cell. I had to scrap a few cells because of poor solder connections.
This week I gave a demonstration of the egg in the bottle to my classes. This is a favorite demo and I always enjoy doing it. This is a good demo when learning about pressure. To start, burn a piece of paper and put it into the bottle and quickly put the hard boiled egg on top. As the fire goes out, the pressure inside goes down and the higher pressure on the outside pushes the egg in.
Here is a link to my last science lab- the hexaflexagon, which we did last week and you can see the video to learn how to construct and add content to the hexaflexagon.
I have seen this egg demo using a small water balloon and it works the same. To get the egg out, you can try to blow into the bottle which has never worked for me. I usually use an Alka Seltzer and water to pop the egg out. I have also used putting the bottle under hot water to warm the air inside the bottle to expand and push egg back out.
Extensions and discussion
It’s difficult for students to visualize a change in pressure until they see this demonstration. Some of the students have experience going under the water and experiencing increased pressure in their ears, and that helps to understand the concept. For the egg here, it’s the pressure difference that pushes the egg in.
Also, be careful to explain that the lack of oxygen alone doesn’t “suck” the egg in. After I question the students, I explain how the egg goes in and then have them explain to their lab partner. At the end of the class, I have them write their explanation on paper about the egg demo and hand it in so I can check for any misunderstanding.
Making and encoding the video
Here is my latest video on the egg in the bottle video. Again, I used iMovie and since the demo is short, I used a movie trailer. This worked out well as the audio has music and the audio from the classroom was very chaotic. I encoded the flv video as the highest level, which gave me a file size of about 39 meg.
This week we built hexaflexagons in class and added science content on each of the four sides. I thought since the water cycle has four main vocabulary terms, it would be creative to put one vocabulary word on each of the four sides. We also used this for the layers of the atmosphere. Hexaflexagons have four sides and can be constructed with only one piece of paper.
This activity builds enthusiasm for learning science and is a good hands-on activity– much like the great bag of science. See the video gallery for all the science videos here.
History of the hexaflexagon
I first learned about hexaflexagon from Martin Gardner when I was in college. In his book, Mathematical Puzzles and Diversions, Gardner shows a few different ways to construct a flexagon and hexaflexagon. Even though Gardner wrote about the hexaflexagons, others are given credit for their discovery. A graduate student named Authur Stone, while at Princeton University, created the first flexagon by playing around with some paper in math class.
This is a fun activity to do when you have four of something. I also did this with another science class with the layers of the atmosphere.
Here is the video on how to construct your own hexaflexagon. I made this video with iMovie and did a voiceover to give directions on how to construct the hexaflexagon. I exported with mpeg-4 as a Quicktime movie and encoded to flash using iSkysoft Video Converter.
How to fold the hexaflexagon
Start with a piece of paper with the length twice as long as the width. From there, follow my video instructions to complete your own hexaflexagon. Students can add content before or after it’s done. We have made both small and very large hexaflexagons in class over the last few years. Using colored markers is easier that colored pencils as the markers don’t press in on the paper. Remember, the better you make the creases, the easier the hexaflexagon will turn. Watch the video for directions.
This week my classes researched and made a volcano to demonstrate to the class. The project involved making a volcano resume and building the volcano. They were to present to the class about the volcano and demonstrate how the volcano works. I only let them use baking soda and vinegar because of safety reasons. They can add some soap and a few drops of food coloring to the volcano which will give a realistic look of the lava.
Careful with other solutions demonstrating the volcano
Don’t let them use Mentos and soda to demonstrate the volcano project as this will create a large mess in the classroom and will attract bugs and insects. The Mentos and soda should be done outside on another project. I don’t think using them for the volcano project is a good idea. See my other science videos on the video gallery page here.
Keep the class volcano projects moving along
To help keep thinks moving along, I employ a few strategies for the classroom.
I keep an index card of each group with their names and class period for each volcano project.
I use the index cards to show the order of who is going first and the next six groups.
When the group project is ready to present, I staple the index card to their grade sheet. This helps keep track of what they did and helps me find the location of this group on the video.
I always require 10 points in the presentation for cleanup of the volcano, ensuring that they learn to help clean up.
I made a grade sheet for each group using this rubric from Science Scope. Use it and change it for your need and let me know how it worked for you. Tweet
Last week we did the great bag of science demo in class. In this video, I get in the bag and a vacuum is used to take out the air. The greater pressure on the outside squeezes the person inside. How much air pressure? Well it’s 14.7 psi. That doesn’t sound like much, but is sure feels strong.
I did this activity with all my students and it was a long day yet lots of fun.
If you have any extensions, comments, or ideas let me know in the comments.
I gave a demonstration of dry ice to my students last week. Here is a video showing what the graduated cylinder looked like at the end of the day. I put a few drops of red food coloring in the water and then put a few pieces of dry ice in the water.
I have this drinking bird on my desk and the kids can’t stop watching it. It keeps drinking the water all day long. As long as I keep adding water to the beaker, the bird will keep drinking. It’s not really drinking the water, just dipping its beak in the water. The water evaporates and cools the beak, thus the liquid moves up.
The temperature decrease causes some of the dichloromethane vapor in the head to condense.
The lower temperature and condensation together cause the pressure to drop in the head (ideal gas law).
The pressure differential between the head and base causes the liquid to be pushed up from the base.
As liquid flows into the head, the bird becomes top heavy and tips over during its oscillations.
When the bird tips over, the bottom end of the neck tube rises above the surface of the liquid.
A bubble of vapor rises up the tube through this gap, displacing liquid as it goes.
Liquid flows back to the bottom bulb (the toy is designed so that when it has tipped over the neck’s tilt allows this), and vapor pressure equalizes between the top and bottom bulbs
The weight of the liquid in the bottom bulb restores the bird to its vertical position
My classes finished the Mars Habitats last week. Everything turned out super. Here is a small video of the final day. Click here to visit my school web site and see a more detailed video.
Here is the rocket launcher that I use for my science class. We build rockets from 2 liter bottles of soda. You can see this rocket launcher in action on the school web site here. If you have any questions, let me know in the comments.
