Surface tension

Here's a little random bit of fun for today: kitchen games with surface tension.

One of the things that changing surface tension does is determine how stable bubbles are. So, let's change the surface tension of boiling water with some common household items.

If you set a pot of water on the stove to boil, the lid will rattle when it gets going, and that's about the extent of it. The bubbles pop quickly and aren't very stable.

If, on the other hand, you set a pot of water with some white rice in it on the stove to boil (and forget to turn it down to low the instant it starts to boil) it'll foam up and boil over and make a great big mess of your stove. If you're one of the other three people left in the world who both cooks rice and hasn't got a rice cooker, you've probably had this happen to you at least once.

A while ago I noticed something interesting: there are certain additives you can put in a pot of white rice that changes the surface tension yet again, so it goes back to not boiling over. My favourite of these additives is ground coriander seed, stirred in while the water is still cold. Also, it makes for some really tasty rice. Garlic powder also helps: while the water still foams, it doesn't grow as tall and boil over as quickly.

Weird water

Water, despite the fact that it's incredibly common, is actually a pretty strange compound. Some of its stranger properties make it particularly useful for life, such as the way it switches from getting denser as it gets colder (normal) to getting less dense as it gets colder (not normal) below 4^oC.

A recently discovered and even more recently characterized weirdness of water is that on the nano scale and on hydrophobic surfaces, water spontaneously flows in instead of being expelled the way one would expect based on the usual reaction of water to hydrophobic materials: (blue in the image below)

What did I learn?

Some random stuff I've learned from my field work: some of this is really blindingly obvious in retrospect, but which I didn't learn in university and thus didn't think of until I ran into it, sometimes embarrassingly face first and sometimes by trying to use an existing bad design.

> Operations and maintenance don't like crawling on their hands and knees on gravel to get at equipment that needs maintenance.

I told you some of these would be blindingly obvious. I have seen limited access to not only equipment for maintenance, but also to valves that need to be used on a regular basis. I have also personally needed to work a valve several times per day where I had to thread my hand between several tubes just to reach it. Fortunately I have skinny hands, and none of the tubes were hot.

What did you learn?

While I was at the National Academies Press website downloading stuff for a previous post, I ran across a title in their catalogue that caught my eye:

Surrounded by Science

Since it was free, and it was about everyday science everywhere and teaching people about science, I downloaded it. Because, you know, Science!

I was nodding right from the first two paragraphs of the preface. Do you remember going to some museum, or aquarium, or other educational and fun location, get interested, have a fun time, then at the end of it get asked by your teachers or parents, "what did you learn?"

And then drawing a blank.

The funny thing is, the first thing I thought of when I read that was actually back in university, when halfway through any given class the professor would announce the date of the midterm: my first thought was usually to wonder what he could possibly test us on, we hadn't hardly learned anything.

I don't know if the book answers the question of how to help kids answer the question "what did you learn?" (I haven't finished reading it yet) but it certainly tries to answer the question of how to help people learn and absorb and integrate science more effectively.

Personally I think instead of asking what they learned, you should ask your kid what were some of the cool things they saw. They'll probably surprise you with the amount of stuff they learned. (I saw a deer with fangs at a museum once. That was seriously weird.)

Magnetic soap

This video demonstrates a nifty advance in surfactant science: unfortunately I can't include it here, so you have to click on supporting information then the .mpg video file link to see it.

What is shown on the right, sticking to the metallic disk being lowered into the liquid, is magnetic soap. (On the left is normal, non-magnetic soap.) The little yellow blob that lifted with the magnet-on-a-stick through the clear liquid and then fell when the magnet was lifted right out of the liquid, is the soap itself.

Three different non-magnetic surfactants were made magnetic by reacting them with ferric chloride, a common industrial chemical.

A solution of ferric chloride by itself also reacts very slightly to magnets, but it finds most of its use as a coagulant, not as a soap.

Violent separation

In keeping with my original plan for this blog, I am now going to teach myself something new.

Here is something I have known about and occasionally seen since I was a kid, and know the name of, but hadn't seen it in operation and didn't actually know how it worked until I decided to write this post and figure it out:

It works exactly the same way as this thing, which I saw for the first time as an adult:

Recycling water

It may be something we don't like to think about, but one of the things the astronauts have to do while in orbit will be coming more and more to Earth. Fresh water is limited, and getting more so with time. Water conservation helps, but it may not be enough in the future.

Whether they are dependent on well water or surface water, many cities have to worry about having enough water to last through the dry season as the water levels drop. Water restrictions are common in some areas; where I grew up, part of the summer routine was that you couldn't water your lawn whenever you wanted, but only on certain days. Sometimes there was an outright ban on watering lawns if the river level was too low.

At the same time, the volume of water leaving a city's wastewater treatment plant is a substantial part of what the city brought in to start with, and grows with population more than the season.

As wastewater treatment technology improves, the sewage plant's discharge gets cleaner and cleaner, so why not use it as feed for our clean water treatment system?

Airplane-induced snow

An airplane made that hole.

Not by just flying through it and swirling the visible cloud out of the way, that makes a different pattern which doesn't last nearly as long.

It turns out that in certain conditions, airplanes can actually induce rain or snow in a localized region of a cloud, and the precipitation is what clears the hole - the water droplets that make up the cloud fall because of the airplane.

Happy new year

Well, I haven't been at this for a full year, but it's been an interesting seven months so far. I've definitely spent a lot more time keeping up with the science news by trying to post something every week. I'm also glad I didn't set out to try to post more than one a week!

I think I'll stick with the Monday post schedule, even if sometimes I have to post something light. I'm also going to try to do more chemistry type stuff; it surprised me how much time I spent outside of chemical engineering and related fields. I also want to do more posts calculating random things, because the ones I've done so far were a lot of fun for me.

Let's see how the next year goes...

Platinum and power

One of the classes I took in university was on electrochemistry and fuel cells. It was very interesting, but was also a reality check on the hype of hydrogen fuel cells vs. the reality. One item in particular that stood out for me was that the catalyst required for efficient, low temperature hydrogen fuel cell operation was platinum. While platinum isn't the most expensive metal out there, gold having passed it in price not too long ago, it's way up there. As I recall, the raw platinum required to make a fuel cell cost a significant fraction of the cost of a normal car, and that was before they processed it into a useful catalyst. Since then, they've improved the structure here and there and reduced the amount of platinum required bit by bit, but it's still a lot.

Not long ago, however, some researchers in Finland figured out a way to reduce the amount of platinum by more than half.