Chlorinated hair

When I signed up for triathlon training, I had to buy a pair of swim goggles so I didn't crash into things like the lane markers, the other people swimming around me, and the wall at the end of the pool. (Ouch.) While buying that little necessity, the sales staff talked me into buying some special chlorine-removing shampoo. Naturally I was curious about whether it was actually significantly different from my normal shampoo or if it was just marketing, which is the majority of the difference between most normal shampoos, so I bought the little sample size bottle to test it out.

Using it in place of my normal shampoo after the swim didn't seem to make a difference that I could notice, but then I did make sure to pre-soak myself in the pool showers before jumping in. Hair absorbs a remarkable amount of water, so getting it to absorb low-chlorine tap water before it hits the high-chlorine pool water will provide some partial protection right there.

I remember my grandfather's white hair turning green when I was a kid and we'd go to the public pool (which I found out as an adult is due to copper from the pipes, not the chlorination). I also remember how the pool smell would cling even after that post-swim rinse.

Anti-fizz

While in Europe on a work trip and grabbing a bite for lunch at a café, I grabbed a bottle of water on my way to pay without checking the label. Checking the label is important, because in Europe, "still" water and "sparkling" (carbonated) water are sold side by side—and I can't stand the taste of sparkling water. Halfway through eating lunch, I opened the water bottle to have a drink and it sprayed water all over my tray and my clothes.

I'd grabbed the wrong sort of water. Not only that, I'd obviously shaken it at some point.

Because I'd opened it, I couldn't return it for a bottle of still water, so I decided to de-sparkle the sparkling water, in the hopes that it would improve the taste. Fortunately, this requires no special equipment and can be done in a café, although it might draw some funny looks.

Natural distillation

I was out snowshoeing with a friend not long ago, and ate some snow because I was thirsty. My friend made a comment about the "distilled water" taste of snow, and I suddenly realized something that, really, I've known all along—snow effectively is distilled water.

Water distillation involves vaporizing impure water, then condensing the water vapour back to a liquid. In the case of snow, water vapour in the air freezes directly into snowflake form, making them pure—distilled—water.

Raindrops, on the other hand, while they also condense out of the water vapour in the air, absorb other vapours into the drop. There are some things that absorb more easily than others, SO₂ being one of the well known pollutant related compounds that absorbs easily into water, and which makes acid rain. It's a little harder (but not impossible) to dissolve other stuff into solids.

Inspired by: bacteria

Here's another one where nature meets engineering on a microscopic scale: tiny submarines small enough to swim through your blood vessels.

Oops, wrong link.

The submarines I'm actually talking about won't carry people, but once built they could be made to carry small doses of medicine, and directed to swim to a specific spot in your body.

The reason this merits a mention in the "nature meets engineering" category is that down at the 10\(\mu\)m scale (which is to say, 100 of these lined up end to end would only reach 1mm long) you can't just build a tiny motor and propeller and expect to have the submarine go anywhere, because at that scale, the physics of it just doesn't work. Instead, what they looked at was how creatures that are actually that small get around.

Boiling with salt

Getting back into chemistry after last week's fun little diversion into mechanics, I feel like doing some more math. I was looking for a recipe not long ago and ran across repeated mentions that one adds salt to water when boiling food in order to raise the temperature at which the water boils, thus cooking the food faster.

Boiling point elevation is a real thing, as is freezing point depression, and it's not hard to calculate.

The boiling point of pure water at sea level is 100^oC. In order to calculate the change in temperature, we need the following equation:

\[\Delta T = K_b m\]

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)

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.

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.

Fake snowflakes

You know how they say no two snowflakes are alike?

It turns out that they're so sensitive to the conditions they form in, and are also fragile in a turbulent area, that the odds of two snowflakes growing in precisely the same way and having the exact same collisions breaking pieces off as they go are pretty small.

There are, however, a few main shapes of snowflakes that all snowflakes follow.

Acid and oxygen

Acid rock drainage is one of the big environmental problems facing hard rock mines, because it keeps going for decades after the mine is closed and abandoned, poisoning everything downstream with the toxic metals leached from the rock. It's a natural process that occurs wherever rock is exposed to oxygen and water; metal sulphides are oxidized by the oxygen to dissolved metal and sulphuric acid. Exposed rock is eventually consumed until there is little to no unreacted metal or sulphide accessible to oxygen.

However, as the process requires oxygen, it couldn't happen until the earth's atmosphere actually had oxygen in it. I haven't yet found a definitive description of what exactly the earth's atmospheric composition was before the change, but the difference between chemistry with and without oxygen is pretty clear, as oxygen is highly reactive and tends to get into everything. For one, the acid rock drainage I mentioned above. Another indication is the type of iron minerals deposited—with or without oxygen, and how much oxygen. As iron combines very easily with oxygen, if you find an iron deposit without any oxygen there's a good chance no oxygen was available to it at the time it was formed.

How much does a cloud weigh?

I was chatting with a friend not long ago, and he mentioned that he sometimes pictured clouds as these malevolant, multi-ton monstrosities hovering overhead, just waiting to smash down on us tiny humans. And by the way, how much does a cloud actually weigh?

Clearly, this calls for some math: I decided to calculate how much a cloud actually massed.

I started out by finding a cloud that I could measure reasonably well.

Inspired by: water striders

Here's another small robot that illustrates a fundamental property of physics. Like the Waalbot I mentioned last week demonstrated van der Waals forces, this one demonstrates surface tension.

Above is a water strider. Notice the dimples in the water where each foot touches the surface of the water.

Snow eater

The Chinook wind is a warm dry wind that comes down from the Rocky Mountains into Alberta, and can turn a winter day into short-sleeve weather in the space of hours. But what heats up the air? It wasn’t that warm on the BC side of the rockies, before it crossed the mountain range. Well, I decided that I was going to calculate it. Let's see if this works.

Let’s say the air comes off the ocean at about 10 degrees Centigrade and 90% relative humidity, which isn't actually typical for a dreary Vancouver winter day—but that's because the Chinook is powered by the Pineapple Express, which is warm, wet air coming inland from Hawaii. It travels inland, raining on Vancouver as it goes, until it hits the coast mountain range, and is forced to rise.

You’ve probably noticed, if you’ve ever changed altitude quickly, that it gets colder the higher you are. Well, that wind from the ocean is going to do exactly that.

To do the math, we’ll look at a small piece of the wind, pretend it stays together to simplify things, and follow it over the mountains.