I am writing this at the request of a friend who insisted it would be of interest.

Really?

Well here goes.

In high school, I had a wonderful science teacher who explained heat transfers to us. To illustrate, he said that in the old days – he grew up on a farm – on cold nights the vegetables and jars in the cold root cellar could freeze.

To prevent this, they used to put a large tub of (cold) water in the cellar. The next morning, the water would be frozen but the vegetables wouldn’t.

“Why?”he asked.

“Because the water absorbs the cold,” we said.

He replied, “Don’t think about cold – cold is the absence of heat. Think about heat. The heat of the water (even though it’s cold water) warms the cellar air the vegetables, preventing them from freezing. As a result, it loses heat and freezes.”

It was a lot easier to think of it that way. That was lesson one.

Lesson two came was another instructive episode. I was microwaving some frozen vegetables. After a minute or two I took them out. They were just thawed but still stone cold. Why? Was the microwave not working?

No, in fact I’d come face to face with something called the “latent heat of fusion.” If I’d measured their temperature after microwaving, even though they were not frozen, their temperature would still be around 0C or 32F. The energy of the microwaves had just gone into melting them, not heating them.

Now here’s the thing. Whenever something goes from frozen to liquid, the “latent heat of fusion” means that as you add heat, as you reach the melting point, the temperature of the substance does not go up. It actually absorbs the heat like a sponge.

So where does the heat go? Well, it’s going into breaking the bonds between water molecules that make a substance solid. They’re rigid and have a lower energy while the bonds that make up a liquid are squiggly and higher energy. So the heat is going into changing the solid rigid bonds to squiggly ones which takes energy – but the energy does not raise the temperature of the liquid it goes intro breaking those bonds. In reverse, think of a liquid as having a huge reservoir of energy that is absorbed as it melts and is released as it turns into a solid.

Which takes us back to the tub of cold water in the cellar – that’s what happened. Even if the water was at zero degrees C, when it was put into the cellar, as it froze it released energy and then turned from liquid water at zero to frozen water (ice) at zero degrees, but only after releasing a lot of energy that kept the vegetables in the cellar from freezing. The latent heat of fusion.

Here’s a factoid: it takes almost as much energy – 80 calories – to melt one gram of ice, vs 73 to take it to 73 degrees Celsius (the recommended temperature for cooking chicken). so to defrost it take as much energy as it takes to roast it!

That’s why you shouldn’t eat snow to quench thirst – it will suck heat from your body, and also why it takes so long to melt snow.

Ok how does this lead to chickens? Well when I’m defrosting a chicken I always put it in the fridge for several days.

My wife asked me – why? You could just as easily defrost it in a sink full of water.

I said, because it’s basically a heat sponge. As it goes from frozen to thawed, it’s sucking up heat in the fridge though the chicken is not getting warmer. That means the fridge uses less energy to keep everything else in it cold. You basically are saving as much energy as it takes to roast the chicken. So given time, I get a nicely thawed chicken, ready for roasting while the fridge gets to take a breather. It’s like putting ice in a cooler – it cools everything else down.

It’s also why when it snows out, the air warms up. As raindrops in the high atmosphere crystallize to make snowflakes, they release heat.

What, you think I’m a nerd?

Guilty as charged.