MinutePhysics

Topics: Physics; Math
Explanation Quality: Better
Medium: Video
Type of Content: Educational

MinutePhysics is a YouTube channel focusing on - you guessed it -physics! All of the videos are time-lapsed drawings (it looks like they are down on a white board) with a voice over. The videos are never very long, usually three minutes or less. Two of my favorites are the video on quantum tunneling and the one on round triangles.

Because the videos are short, watching them is a fun way to learn a bit about a lot of different areas of physics. Last year, when the LHC discovered the Higgs Boson like particle, MinutePhysics made a few videos explaining what the Higgs Boson would do and why it was important. Some of the videos cover common physics misconceptions. Overall, I really like the way he both explains and illustrates his points. It really helps my understanding. And since the explanations and drawings often have a bit of humor, that makes me like them even more.

Basically, if I have nothing to do, I can go check out MinutePhysics and consistently be both entertained and educated. So go check it out!

Rising Heat

Hot and Cold

• blue or green colored ice
• red food coloring
• warm water
• large container

Make blue or green colored ice (see the beginning of Mixing Colors for an explanation). Fill the large container with warm water. Make sure the container is as still as possible (as in, not on a rickety folding table). Try to minimize it's movement throughout this activity. On one side drop in a few ice cubes, on the other side put in a few drops of red food coloring. Now observe.

The red is hot water and the green is cold.

You can talk about a few things with this activity. One is why the food coloring spreads out instead of just staying where you dropped it. This is because the molecules in water are always moving. Their movement knocks around the food coloring molecules and causes them to spread out. You may also notice that the red spreads out faster than the blue. This is partly because the blue starts out trapped in the ice, but also because the molecules in the hot water are moving faster. Heat is energy. If you have more energy, you move around more. The same is true for molecules. So the faster moving warm water molecules knock into the food coloring more than the slower moving cold water molecules, thus spreading the color around faster.

The main point of my explanation when I did this was about the layering of the colors (I had this as part of my weather themed activity set). If you don't disturb the water, eventually the red water will be in the top half of the container, and the blue water will be in the bottom half. This is because the blue food coloring is staying with the cool water, and the red with the warm water. The reason the different temperature waters separate is because of density. Density is mass/volume, or how much stuff there is in a certain amount of space. Hot water is less dense than cool water. My friend had a really good intuitive explanation as to why this is true:

Think of a bunch of kids sitting at a table. Right now that don't have much energy, so they stay where they are. Then you give them a bunch of energy. Now they are probably running all around the room, and only a few are still at the table. The kids represent the molecules in the fluid. The energy you give them is heat. The table is the space we're comparing. In the first case there are a lot of kids at the table, or a lot of stuff in the area, so it is pretty dense. In the second kids, only a few kids are at the table so there is less stuff in the area and the density is lower.

Learn More:
http://www.landa.com/docs/HotWatervsColdWater.pdf
http://www.mansfieldct.org/Schools/MMS/staff/hand/atomsheat.htm
http://phet.colorado.edu/en/simulation/density
 

Scientific American

Topics: Science (Biology, Chemistry, Physics, Linguistics, Computer, etc.); Engineering
Explanation Quality: Best
Medium: Print, Graphics
Type of Content: News

Scientific American is my favorite magazine. I've been subscribed for the past three years. I always get really excited when I see that it has arrived in the mail. Every month the have several feature articles on some new, recent topics. Occasionally, the article is themed and all the featured articles are related. For example, the September 2013 issue is all about food - looking at it from nutritional, ecological, and historical perspectives, among others.

They also have specific columns every month, such as the Science of Health and TechnoFiles. I really enjoy SA because it has a nice variety of articles, and I can learn things in fields that aren't my main interest. I also find it convenient that I can bring a magazine with me to read when I don't have internet.

It is also a very reliable source. I don't need to bring my usual skepticism when reading SA because the writers of the articles are (for the most part) scientists who were involved in the research. 

If you can't subscribe yourself, see if your library does. It is also worth checking out their website as they have some full articles there as well.

EdX

Topics: All (Business, Sciences, Philosophy, Economics, Engineering, History, Law, Humanities, etc.)
Explanation Quality: Best
Medium: Video, Text, Powerpoint, Interactive exercises, Problem Sets
Type of Content: Educational

EdX is a collection of free Massive Open Online Courses (MOOC's). If you've never heard of them, MOOC's are courses (normally college courses) that anyone, anywhere can take as long as they have access to the internet. Carnegie Mellon University's Open Learning Initiative is another example of them. However, there are a few key differences. One is that edX currently offers a total of 50 courses from13 different schools. If a course has already finished running, many still allow you to look through the lectures and notes. Most courses will give you a certificate of mastery upon completion. Overall, these are more like taking a real college course, just online.

A screenshot from my Quantum Mechanics class

I am currently signed up for a class on quantum mechanics from The University of California, Berkeley. It runs for 10 weeks. 8 of those weeks are classes, one is a midterm, and one is a final. Every Saturday the material for the next week is released. This is two video lectures (though each is broken up into smaller segments), a copy of the course notes, and a set of homework problems. If you want credit for the homework, it has to be completed by the next Sunday. You can audit any course and simply watch the videos and read the notes, but if you want a certificate, you need to get at least a certain grade. In my course this is an 80%.

There are several other helpful features. The discussion forum is really helpful if you don't understand something. There are also TA's who occasionally post hints or other useful information. In other courses, there can be interactive labs. For example, some chemistry courses have a molecule editor which allows you to "create" molecules in order to answer questions, or just get a feel for how things work.

So far, I really love this site. If you want to learn a new subject, this is definitely a good place to check out. Not all of the courses are entry level though. Each will state its prerequisites on its main page. For example, my course requires knowledge of linear algebra to complete. But it is still worthwhile to check around, even if you don't have anything in particular you want to learn. You map find something that surprises you.

Icy Fun

These activities all involve ice and color to help cool down the last few days of summer.

Some green ice.

Mixing Colors (for young children)

• food coloring
• water
• ice trays (or small containers to freeze the water in)
• bowls/cups (preferably light colored or clear)

You need to make ice cubes in several different colors. To this, first add a few drops of food coloring to some water, mix it, then pour it in the ice tray and freeze it. I assume if you don't mix it, the food coloring won't be evenly distributed, but I haven't actually tried. That might be another experiment you can tie in - seeing how the ice looks when the food coloring wasn't mixed. Have at least the primary colors, but use more if you want!

Then pair up different colors in different bowls. As the ice cubes melt, the colors will start to mix. See if the kids can guess ahead of time which colors will form. Once you've done it with just pairs of colors, try it with three different colored ice cubes.

Rainbow Tunnels

• food coloring (or other form of liquid color)
• salt
• water
• large-ish containers

Freeze several BIG ice cubes using the large containers. If you want your ice cubes to have more interesting shapes, you can fill a balloon or plastic baggie with water and freeze that. You will probably have to leave them overnight. When you actually want to start the activity, do it outside or in a large box - somewhere you won't mind things getting all wet.

Image from artsandcreativity.blogspot.com

 In several small dishes, put a bit of water, salt and food coloring. Set yourself up with a nice variety of colors. Now the fun begins! Start pouring the colors onto the ice. Don't pour too much at once, an eyedropper or even a spoon would be helpful. Also BE CAREFUL. Salt lowers the freezing point of ice, so the ice gets colder . If you have salt on your skin and then put ice on it, you can get a minor form of frostbite. So I would not recommend touching these ice cubes or the salt water colors with your bare hands. It is the salt lowering the melting point that makes this work (it is also what allows you to make your own ice cream). When you add salt the ice immediately around it starts to melt. The salt then slowly melts a tunnel through the ice. If you do this outside, not only will the warmth help melt the ice cubes faster, the light makes the ice cubes look really cool (no pun intended).

Learn more:
http://antoine.frostburg.edu/chem/senese/101/solutions/faq/why-salt-cools-icewater.shtml
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch15/colligative.php
http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/meltpt.html#c1