The Bombardier Beetle And Its Crazy Chemical Cannon | Deep Look

Biology is freaky weird.

The bombardier beetle is terrifying. It's got three chemicals that are kept separate within its body until it mixes them which releases a ton of energy, heating and pressurizing the mixture into a boiling liquid that the beetle can squirt out of its...um...probably not its butt, but I'm not an entomologist 

The Hidden Danger Inside Every Candle

This is this third time I've posted a video about this demonstration, one I still haven't done in my own classroom.

I don't know that the action lab does a better job explaining things, but he certainly does a better job filming the flaming cloud from up close.

Mpemba effect

Yesterday I mentioned the real phenomenon of ice droplets freezing from near boiling before hitting the ground if thrown up into really cold air.

Today, some videos of that happening along with the scientific explanation of the Mpemba Effect.

The above video is one of the prettiest I've ever seen of the effect, though there are others - after the jump - that explain the science better.

Ice Spiral Math

Let's be honest, we should all be more skeptical about videos that we see online.

Yes, there are some really cool videos online. Some of them are real, honest videos of things that actually happened.

Others, however, are bullpucky like the above video of a young woman supposedly pouring boiling water out of an electric kettle and the water freezing into a free-standing spiral before it hits the ground.

This is mocking - or maybe just playing off of a real effect in which boiling water - if thrown into ridiculously cold (like -30 F) air - can freeze before hitting the ground. It does require the water to be nearly aerosolized into really tiny droplets, drastically increasing the surface area allowing for much faster cooling...more on that tomorrow (ooh, a teaser!)

As I said, we should be skeptical. I don't know, however, that we all need to take that skepticism to such mathematical, analytical depths to publicly debunk such videos.

But thants, learnwithsherlock.

Paraffin Wax Autoignition

I've posted a couple of videos of this demonstration before, but this one does a better job explaining how to do the demo than those others did.

As always, let's be careful out there, folks.

Dip your hand in molten lead without being burned!

"Don't try this at home," isn't enough of a warning for this.

Adam Savage recently answered a question about this video asking whether it was as surreal an experience as it seemed.

Adam said, 'yes', it was and went on to explain why it works, why they were understandably afraid of it, and how they slightly cheated by wetting their hands first.

There's a lot of explanation about the leidenfrost effect and how it protected their hands (and hot dogs), but the short version is that if the surface is hot enough relative to the liquid, enough of the liquid can instantly boil, creating a cushion of boiling gas between the liquid and the solid surface, sort of protecting the two from each other.

That's all well and good - as well as an explanation of how walking on hot coals works - but I'm still not sure I'd trust myself with the molten lead.

What is Fire?

Fire is awesome.

That's a simple enough answer, isn't it?

This video - with its oddly-voiced, slightly-speech-impedimented (or maybe just a British accent), and weird narrator - explains a bit of the history of elements and then goes through the parts that really make up the fire: fuel, gas, light, heat.

In the end, the answer to the video's titular question is this: Fire is actually the visible side effect of what happens when matter undergoes a change of state by means of a chemical reaction. (at 1:15 in the video)

Fundamentals of Science: Heat versus Temperature

Heat and temperature are not the same thing.

Man, if I could get 100% of my students to understand that distinction, I would feel like my themochemistry units were fairly successful.

Yeah, there are other details here and there, but really, that's a pretty big idea right there. Heat and temperature are not the same thing.

Serious Eats just put out a cookbook under their The Food Lab label, and one of the introductory chapters - specifically the one dealing with this heat/temperature distinction - is available for free online.

They, of course, focus on what that distinction means for cooking...

The article goes through the methods of heat transfer: radiation, convection, and conduction.

They also discuss some differences in cooking vessel material, specific heat and heat capacity, and relevant reference temps (for freezing, boiling, and germ killing). Plus they describe an experiment to show the difference in energy transfer rates between water convection (a pot of cold water heating to boiling) and air convection (a 200 Fahrenheit oven), both of which are tested with your hand and a thermometer.

From the article's finale...

To sum up:

• At a given temperature, denser materials generally contain more energy, and so heavier pans will cook food faster. (Conversely, it takes more energy to raise denser materials to a certain temperature.)
• At a given temperature, materials with a higher specific heat capacity will contain more energy. (Conversely, the higher the specific heat capacity of a material, the more energy it takes to bring it to a certain temperature.)