Princeton Journal Watch

Topics: Science
Explanation Quality: Best
Medium: Text
Type of Content: Research, News

Princeton Journal Watch is a blog about research conducted at - you guessed it - Princeton University. Each post gives a description of a recently published research article. They seem to come from all the (science) departments of the university. It is a good way to see what new discoveries are happening. The other great thing about it is that all the posts are written so that a layperson can read them. In other words, even if you don't have background in the topic, you will still understand what the research was about. A lot of the things are really interesting. To get an idea of the type of stuff they have, they last few posts they wrote (at the time of my writing this) are: "Princeton Researchers Use Mobile Phones to Measure Happiness"; "How Will Crops Fare Under Climate Change? Depends on How You Ask"; and "A Faster Vessel for Charting the Brain". All the posts link to an abstract of the article. The only downside is you (usually) can't read the full article without buying it. But I don't mind, because I don't have the background to understand the actual articles anyway. So overall, it's a good place to go for some easy to understand information on complex topics.

States of Matter

These four occur naturally:

Solid: has a fixed shape and volume. The composite particles are very close together and don't move much. Solids can be crystalline or amorphous. Crystalline solids are very ordered. The atoms inside form a repeating structure. Examples are snowflakes and amethyst. There are also amorphous solids. The atoms are very disordered. An example is glass.

Liquid: has a fixed volume, but not a fixed shape. It will fit the container it is in. The composite particles are still close, but they can move around each other more. Examples are water and paint.

Gas: neither a fixed volume nor a fixed shape. It will fill any container you put it in. The particles can be close or very far apart, depending on how much pressure they are under. Examples are water vapor (steam) and oxygen.

Plasma: an ionized gas, full of electrons and ions. Neither a fixed volume nor a fixed shape. Read more about it here. Some examples include lightning and the sun.

Clockwise from top left this shows solid, liquid, plasma, and gas.

However, there are also other things that don't quite fit into any of these categories.

Open Learning Initiative

Topics: Assorted
Explanation Quality: Best
Medium: Text, Practice Exercises
Type of Content: Teaching Material

Open Learning Initiative (OLI) is part of Carnegie Mellon University (CMU). It offers free online courses that anyone can take. While there are only 18 at the moment, they still cover a variety of topics.

There are a couple of things about OLI that I really like. One is simply the style of the courses. They are written in a very accessible way. They are all self-paced. It starts out with a syllabus, and then a brief section with suggestions on how to most effectively use the online course.

The course is mainly composed of written explanations, sort of like those you would find in a textbook. At the beginning of each section is a description of what you will learn in that section. There are little exercises you can do to see if you understand the material (that's the "Did I Get This?" box in the picture). Most of the courses are introductory level, designed to be taken if you have little or no prior experience (or if you haven't thought about the subject in a long, long time).

I have personally been working my way through the Statistics course and the American English speech class. Although I'm only taking the Speech class for fun (technically I'm taking them both for fun, but I do seriously want to learn statistics, I just haven't been able to take a real class at school yet), I find it pretty interesting. To help show the correct way to pronounce things it offers audio files to listen to and diagrams to illustrate what is happening with your mouth and throat. The statistics class is more like a typical math class, with explanations and problems.

This is not a good website if you only need to look up a quick explanation for your chemistry homework. It is a good website if you want to seriously learn about a subject, if you are taking a class in it but your teacher is really bad at explaining so you want another resource you can use simultaneously, or if you found a new subject you think is interesting but you don't even know what you don't know and so have no idea where to start. If any of those sound like you (or even if they don't) it is worth checking out.

Working with Homefront

For the past month or so I have been going down to a summer camp for underprivileged kids to run science activities. It's a really nice place. They spend the morning working on academic things (one day I saw some kids playing math basketball!), and in the afternoon they do more typical summer camp activities like arts and crafts. So I got to come in as a "bonus" academic activity. I took took the kids in smaller groups.

Fun with Glurch

Every time I went I got a different age group.  I first had the teens, then 5th and 6th graders, 3rd and 4th graders, and then the kindergarten through 2nd graders. The first four times I went, I did pretty much the same activity set I did with my other afterschool program. The experiments were matter themed - first we did chromatography and talked about what molecules are and the fact that they move around. Next, we made Glurch and discussed its different properties, and why each one ended up slightly different (because I don't have time to accurately measure the ingredients, so it's all estimating). With the Oobleck, we could talk about states of matter. The straws didn't really relate to the matter theme, but we used them to teach about sound. And it was a nice, not too messy way to wrap up.

HyperPhysics

Topics: Physics, Math
Explanation Quality: Best
Medium: Text
Type of Content: Teaching Material

HyperPhysics is an interactive concept map. You can either search a specific topic, or just find it by following the path. One thing I really like about it is that if in the explanation of a concept, if they use a word for another concept you don't understand, you can follow the link from that word to an explanation of that idea. I find this really convenient.

None of the explanations are very long. They are in nice, manageable chunks. The information is also trustworthy, as it comes from Georgia State University. In general, information that comes from university websites is accurate.

There is also a small side branch of HyperPhysics called HyperMath. It is not as complete of a resource as HyperPhysics is, but can still be useful.

National Night Out

National Night Out is a (presumably national) event held the first Tuesday in August to promote anti-crime organizations and the like. But they also have other community members run booths, and in my town I got to be one of them!

My set-up was pretty similar to that of the local fair I did a few months ago. I was having the kids make Glurch, but I also had a bowl of Oobleck out as a demo they could touch.

Some statistics:
I brought a total of 26 oz of glue, and by the end I had used 18 oz.
I had about 75 kids come by to make something (I only had 25 cups left from a pack of 100).
The colors in order of popularity were blue, green, pink/red, yellow. I actually ran out of blue food coloring.

Here's the sign I put on my booth.

One of the glue bottles was of clear glue. I think I actually preferred it to the white glue, at least in terms of looks. The resulting Glurch seemed a bit stickier and goopier, but I ran out of the stuff before I could really see if that was the case. So sometime soon I want to compare the two (with accurately measured proportions!) and see if there are any differences.

My one big problem with doing the Glurch is that I don't actually measure the amounts out. The cup is filled up to a certain line, but then the water and borax are just kind of thrown in. This makes the proportions slightly different in every batch and leads to some being better than others.

Additionally, with the Oobleck you have to mix it occasionally, because I've found that the water and cornstarch tend to separate.

Unfortunately, this time I forgot the recipie cards. Which is a shame because some people asked me how to make it at home. But I did bring plastic snack bags for them to put their finished Glurch into.

ViHart

Topics: Math, Music
Explanation Quality: Good
Medium: Video
Type of Content: Recreational

ViHart is a self-proclaimed "mathemusician". She makes lots of short, fun videos discussing math and sometimes music. While these are in some sense "educational" they are not going to help you review something from math class. In fact, the set-up for many videos is the doodles you can make while bored in class.

This isn't to say they aren't a worthwhile watch. I love hexaflexagons - I have quite a collection floating around. ViHart shows more of the fun side of mathematics, which is something you don't get to see in school unless you're pretty lucky.

How Much Water Fits On a Penny?

Materials:

• penny
• eyedropper or pipette (if you don't have one this article explains how to make one)
• water
• other liquids
• soap

Make a chart like this (or feel free to copy this one and print it):

Liquid	Predicted # of drops	Actual # of drops
1.
2.
3.
4.
5.
6.
7.

My supplies

For each liquid, you are going to use your eyedropper to carefully drop the liquid onto the penny until it spills over. Record the number of drops that fit. Try and make a prediction before you do it each time.

You can use any and all liquids you want (assuming they are non-toxic obviously). However, make sure you try this with both normal tap water and soapy water. And be sure to wash and dry your penny between each new liquid (and rinse off your dropping device as well).

What's Happening?

The atoms/molecules in a substance are all attracted to each other through intermolecular forces (IMFs). This can be because the molecules are polar (meaning one side is slightly more positive than the other) such as with water. Or it can be because the molecules are big enough that the electrons moving around can induce positive and negative poles. Whatever the reason, when the IMF is between molecules in the same substance, it is called cohesion. So all the molecules on the inside of the liquid are attracted to all the molecules around them. However the molecules on the surface of the liquid don't have any molecules above them to be attracted to, so they are more attracted to the molecules on the inside. This forms a "film" on the surface and keeps the liquid together in a drop.

Since water is polar, and therefore has high IMFs, its surface tension is relatively high. So more water should be able to fit on the penny before the surface film "breaks" and the water spills everywhere.

Image courtesy of factfixx.com

Here's my data chart:

Liquid	# of drops
1.       Water	24
2.       Water	26
3.       Soapy water	23
4.       Milk	22
5.       Salt water	14

Huh... not what I expected at all! Except for the salt water, the number of drops is pretty similar in each. So either the explanation I just gave was wrong, or something happened in the experiment that I didn't account for. Even though the number of drops was the same, I definitely felt suspicious because the blob of soapy water on the penny just didn't look as big as the one from normal water had been. I also felt like the size of the drops were smaller. So since I was using a syringe with volume measurements marked on the side, I filled the syringe up to 1 mL each time and after I had finished dropping on the penny, I continued counting drops until I had emptied the syringe.

So here's my new data table:

Liquid	# of drops	# drops in 1 mL	Ratio
1.       Water	24	23	1.0
2.       Water	26	19	1.4
3.       Soapy water	23	46	0.50
4.       Milk	22	27	0.81
5.       Salt water	14	22	0.64

Now the results make a little more sense. And it does make sense that the drops would be smaller - they have less surface tension to hold them together. I find it interesting though that none of the websites that reminded me of this activity (this isn't the first time I've done this, I actually distinctly remember doing the penny water drops experiment in 3rd grade) mentioned this fact. It might have just been the syringe I used. If anyone else tries this, I'd be interested in hearing how it worked out.

Learn more:
http://hyperphysics.phy-astr.gsu.edu/hbase/surten.html#c4
http://www.chem.purdue.edu/gchelp/liquids/tension.html 

Khan Academy

Topics: Math, Science, Economics, Computer Science, Humanities
Explanation Quality: Better
Medium: Video, Practice Problems
Type of Content: Teaching Material

Many of you have probably already heard of Khan Academy. It is a website offering short videos and practice problems in a variety of subjects. It was originally created to help the creator tutor his cousin over the internet. The videos feature someone (in many it is the founder Sal) giving a short (under 20 minute) explanation while writing it out on the video screen.

There are videos in economics, math, history, and the sciences. There are only practice problems in chemistry and math, but the difficulty ranges from telling time to calculus. I find the practice problems very helpful. The videos are good too. He attempts to explain each thing in several ways, and does examples in the videos. I have one minor problem with them: I often watch videos to review something from class or to compile all the bits I have learned from different sources. So parts of the video are new things/things I didn't understand, and parts I already know. I end up not wanting to watch the parts I already understand, but I don't want to skip forward in case he mentions something else new. But as I said, this isn't really a big problem.

If you make an account, watching videos and doing problems earns you points and achievements which is a fun additional motivator. They also show stats of how much you have been working on skills or watching videos. Personally, I love things that chart my progress.

If you are a parent/teacher/helpful older sibling, you can monitor your child/student/younger sibling's progress. I have my little sister's account registered as a child account under mine so I can make sure she is still doing work over the summer. When I see that she hasn't done her tasks for the day (she is supposed to learn one skill of her choosing every day to make sure she is doing something educational with her time) I can then react appropriately. But don't worry, you don't need a coach or mentor to use this site. It is good for anyone who wants to learn something.

Brilliant

Topics: Math, Physics, Computer Science
Explanation Quality: Good
Medium: Problems, Text
Type of Content: Recreational, Practice Problems

Brilliant.org is one of my favorite math websites. It offers a a new set of problems every week in a variety of topics. Before you start doing problems in a certain topic, you do a few problems to determine your level. The site then places  you appropriately and you can get started with this week's problem set. You level up if you consistently do well.

What I like about it is that the problems are interesting. You don't immediately know how to go about solving something. I always end up with a few problems I can't figure out. At the end of the week, you can view solutions to all the problems. You can also offer your own solutions and help out others who didn't get it.

While the main section of the site has olympiad type problems, there is also a practice section where you can choose to work on specific techniques. It is helpful for reviewing topics from school. It also actually explains methods of solving the problems, instead of just throwing you in there. I personally don't use that section as much, because I have more fun with the main problem sets. There are also smaller weekly problem sets in physics and computer science. I expect the sections to expand in the near future but for now the bulk of the site is math.

So head on over and have some fun!