Why do hot
things smell
stronger?

The full narration of the video.

Cold leftovers barely smell. Heat them up, and the whole room knows. Last night's braised pork, straight from the fridge: you lean in and catch only a hint. Two minutes in the microwave, and you can smell it across the living room. Same pork, not a gram of spice added. So what exactly got added?

To smell something, a few of its molecules have to fly into your nose. These molecules are far too small to see. They hide in the meat and the sauce, packed together. And they never sit still. They jiggle and bump, all the time.

But escaping isn't easy: the molecules around it hold it back, like a bar set above its head. Think of it as the high jump. Only the ones that jump high enough clear the bar and fly off into the air. When the food is cold, nobody has much energy. Only a stray few make it over.

Heat it up, and the whole crowd jiggles harder and jumps higher. Suddenly far more of them clear the bar. More aroma molecules in the air means more reach your nose, and you think: that smells great. That leap over the bar has a name in physics class: evaporation.

Leave a bottle of alcohol open and in a few days it's lower. A puddle dries up in the sun. That's evaporation too. The bar is the pull of the molecules around it, and how high they jump is the temperature. The hotter it is, the faster things evaporate. Researchers served the same coffee at temperatures from about thirty to over sixty degrees, measuring what drifted up from the cup while tasters sipped.

Above forty degrees, noticeably more aroma molecules came off. Above fifty, some of the roasty ones rose the most. And the tasters agreed: the hotter cups tasted more roasted. Heat helps in one more way: hot air rises.

Open the microwave, and a puff of warm air carries the molecules up, right to your face, then slowly through the whole room. And each kind of molecule has its own bar height. Perfume and alcohol have a low bar, so they hit your nose even cold. Many of the meaty smells have a high bar, and need heat to get out.

The same goes for eating. Aromas float up from the back of your throat into your nose, and cold food sends up less, so it tastes flat. That's not the whole story. Your tongue tastes sweetness better when it's warm, and fresh off the stove, the heat is still making new aromas in the pan. It works the other way, too: the colder something is, the fainter it smells.

Iced coffee smells weaker than hot coffee. Chill a red wine too much, and its aroma goes quiet. So which do you reach for: iced coffee, or hot?