Cincy Science: Asphalt that melts like butter? The 'fried egg on sidewalk' trick? When hot is hot!

CINCINNATI - Ever ask, "What is that?" Or, "Why is that?" In our "Cincy Science" feature, we talk with people who can answer those questions: The folks who do science in Cincinnati and the Tri-State.

When temperatures soar, it impacts our everyday lives. To get some insight into the effect of searing heat and how to be aware of potential repercussions, we consulted University of Cincinnati distinguished professor of chemistry, Bruce Ault.

Q&A: Just how hot...?

1. So from a chemistry perspective I guess excessive heat impacts a number of substances outdoors, say for instance asphalt?

I know exactly what you mean. It applies here as well, but when I grew up as a kid in the California desert, when asphalt gets hot it gets really soft, so soft the kickstand on my bike would simply sink into it. That’s exactly what’s happening, it’s not like an ice cube that’s melts at a definite temperature.

It’s more like a stick of butter if we leave out, it will melt over a range of temperatures. Asphalt does the same thing because it’s a mixture of chemicals, but it gets softer and goes into a liquid like or nearly liquid like state that can have ramifications for things that are parked on it or driving on it.

2. What about it being hot enough to fry an egg on the sidewalk, is that actually possible?

It’s possible, but that’s difficult. The other thing I should have said about asphalt is it’s black and things that are black absorb all wave lengths of radiation - so that radiation from the sun is what’s causing the heat. Something that is black (and since I drive a black car I feel it there also) but black surfaces in particular absorb all of the sun’s energy and heat up faster than things that are white that reflect the sun’s radiation. So if you’re going to fry and egg, I would much rather do it on asphalt or it would be much easier than to fry it on concrete.

3. When you brought up reflective surfaces, it made me think of a story from London last year where developers built a reflective skyscraper that was actually melting cars . Is that unusual?

I remember reading about that and I had never heard of anything like that before. I believe it from a scientific point of view, but I never would have guessed it and clearly the architects didn’t have it figured out. One of kids' science fair projects is often to make a solar cooker, and a solar cooker basically is a black box; black because it holds the heat and then some sort of lens to focus the sun’s energy in a single spot.

From what I understand, the building was doing very much the same thing. The reflective surface was tending to act like a lens, focusing the sun’s radiation on a fairly narrow point in space and that point in space got very, very hot. Hot enough to melt a car.

4. If excessive heat melts asphalt and reflective solar rays melt cars, I’m guessing too much heat isn’t good for the human body?

It’s a little out of my realm, but clearly it can affect biological function, because there’s a narrow temperature range which a biological organism can function effectively.

We have built in heat removal mechanisms, sweating being the primary one, but those are only effective up to a particular degree. And certainly in this part of the world where’s there high humidity our ability to sweat and to cool our body through evaporation from sweat is limited because you can’t evaporate water as quickly when the humidity is high. Where I grew up in the desert, where it was very hot most of the time, it was very dry so sweat was actually a very effective cooling mechanism.

5. Growing up in the desert, did you ever encounter temperatures too hot for airplanes to take off?

Of the major airports, I would say Phoenix and maybe Las Vegas come to mind. Those are the areas when your temperature is up in the 110 or 120 range, so you don’t get enough lift to be able to take off. As air expands density decreases, which is why hot air rises and cold air sinks.

6. Can you think of any other type of impact excessive heat may have on our everyday lives?

One of the repercussions is the overloading of electrical grids, which comes simply from the fact when it gets excessively hot we all turn on our air conditioners and we run them hard and heavy all to stay cool and we’re doing it at the same time. That really loads or in some cases overloads them in some cases.

Q&A: In Cincinnati, Duke Energy spokesperson Sally Thelen explained the grid is well prepared to take on the summer heat.

1. How does Duke Energy prepare for a potentially excessively hot summer?

The critical most important thing that we do to maintain the reliability of our clients is we do off peak maintenance at our plants, on our infrastructure. So in the spring and the fall typically when you’re not experiencing you’re extreme hot or extreme cold temperatures, we’re able to get out there and make necessary repairs, upgrades, changes and make sure the grid is working as optimally as possible for us as well as our equipment.


Is there any possibility of black outs or brown outs from overloading the grid?

No. We’ve got a very robust system here. We also have programs in place that enable us to shed load in the event we get into a high usage pattern.

And we have demand response programs for people like Power Manager for people’s homes that cycle off their air compressor for example on their air conditioning unit, just a few minutes every half hour. Typically it doesn’t even make a home owner aware in terms of the temperature change in their home because it’s so subtle and so brief. But it’s a way for us to help relieve a little bit of the load on the grid. We do that residential customers, we also have a similar service for our business and industrial customers. So we have mechanisms in place in the event we need to quickly shed load, we certainly have a robust plan in place that we would be able to meet the demand.

3. So the program saves customer's money?

It’s not going to make you rich, but it certainly is a way to help maintain the viability of the grid. I will give you a little bit of extra spending money in your pocket: $25 to $35 when it's used, plus an initial activation credit. It’s a great program that activates no more than 10 times in a season, so it’s been something we don’t usually max out the number that are activated, but it’s a nice thing for us to have in the event we need to use it.

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