Topic
Heat
13 articles
Chemistry
Why can’t you un-fry an egg?
Melt butter and it sets again when it cools. Heat an egg white and it turns from clear jelly to white rubber and stays there forever. Nothing was added, nothing escaped, and in 2015 a laboratory in Australia partly reversed it anyway.
Chemistry
Why does blowing kill a candle but feed a fire?
One breath ends a birthday candle. The same breath, aimed at a campfire, makes it roar. Nothing about your lungs changed in between, so the difference has to be hiding inside the two fires.
Chemistry
Why can hot water freeze faster than cold?
A schoolboy making ice cream noticed that his warm mix froze before everybody else’s cold mix, and got laughed at for saying so. Sixty years later the argument is still running, which makes this a rare thing — a question you can genuinely still lose.
Technology
Why does your phone die in the cold?
You go outside with a healthy battery and the screen is black within twenty minutes. Bring the same phone indoors, plug in nothing at all, and most of that battery comes back. Nothing was ever spent.
Physics
Why does metal feel colder than wood?
A metal chair leg and a wooden tabletop stand in the same room, in the same air, at the same temperature. Touch them one after the other and your hand insists that one of them is freezing. Your hand is not lying — but it is not measuring what you think it is.
Physics
Why does a desert get so cold at night?
Sand that could blister a bare foot in the afternoon can be chilly enough for a coat by midnight. All that heat goes somewhere, and where it goes is not where most people guess.
Astronomy
Why is Venus hotter than Mercury, when Mercury is closer to the Sun?
Mercury sits nearer the Sun than any other planet, so it ought to win. It does not, and the planet that beats it is almost twice as far out. Distance turns out to be the least interesting part of the story.
Chemistry
Why does a cake need baking powder?
Leave it out and the cake comes out flat and heavy, and nothing else in the bowl has changed. So what is half a teaspoon of white powder doing that a pound of flour, sugar, butter and eggs cannot?
Physics
Why is the back of the fridge warm?
Reach around the back of a refrigerator and the metal is warm. The one machine in the house whose whole job is making things cold turns out to be heating your kitchen, and the reason is sealed inside a pipe.
Chemistry
Why does toast taste different from bread?
Nothing goes into the toaster except a slice of bread, and the slice comes out lighter than it went in. So where does the smell of toast come from?
Physics
How does sunscreen stop a sunburn?
Rub it in and you can still see your skin, still feel the sun, still get warm. Nothing looks blocked at all. So what has that invisible film actually done?
Chemistry
Why does popcorn pop?
A pan of hard yellow beads goes quiet, then starts firing. Nothing is added to it and no kernel gains a single gram. So where does all that white come from?
Technology
Why does a lightbulb blow the moment you switch it on?
Bulbs almost never quit while they are quietly glowing. They wait for the flick of a switch, then go with a flash and a small tink. Something about that first instant is rougher on the wire than a whole evening of burning.