# Could a can of cola stay cold for two days?

17 May 2016

## Question

After a cookout on Saturday, I left two cans of Coca-Cola in my bag. Around Monday morning which is almost two days later, when I left for school, the cans were still cold with moisture on it. My mom found the cans and thought that I had taken them out of the refrigerator and was planning to take them to school. We started arguing about how she believed I was lying and that it wasn't reasonable that would happen. The next day, she told me to put another can of Coca-Cola in the car and only leave it overnight to see what the result would be. Completely contrary to what I firmly believed it would feel like, it ended up being warm. Therefore, my mom put me on punishment and won't let me off until I find a reason that the can was cold. The temperatures on the Saturday were 53 degrees. The temperature on Saturday was 58 degrees. The temperature on Sunday night and early Monday morning when she saw the cold cans was 53 degrees. The temperature on the Monday night and early Tuesday morning where the warmer can was analyzed was 63 degrees. Can you explain why this could've happened. Please help me, I haven't been able to have any electronics except for the computer for 3 weeks now.

We asked Gerry Gilmore to help get Tacari out of trouble...

Gerry - Well the simple answer is that a can of cola, which you shouldn't be drinking for health reasons, will come to equilibrium in temperature with the environment very quickly indeed, because it's a very thin metal and it's just basically water and sugar on the inside, so it will quickly come to the ambient temperature. But that's irrelevant, the point is why does something feel cold? Something feels cold because it conducts heat away from your skin efficiently. So, on a cool-ish sort of day, if you touch a thin metal sheet it will feel cold to you.

Whether the second part of this was there was moisture on it (condensation), so therefore it was cold. Condensation has nothing to do with temperature, it's to do with humidity and so, if there was a cool-ish damp day, the cans could well feel damp and cold and that would just be their natural temperature.

Then there's the interesting follow-up of the car. Now, cars are interesting because cars over-cool at night time. That's because of their windows which radiate away more heat than is natural so cars get colder than their surroundings, which is why there's always ice on your car and not on the grass. But then they heat up more quickly than their surroundings as well. And so, if you went to check your can early in the morning in a car it would have been colder, and it would probably have frost on it, and he would have won the discussion, but doing it a little bit later means you lose.

So, the real answer is: a) by not having the cola for however long one was grounded and not having the other prohibitions, his health and general education has improved enormously. And secondly, there's three interesting bits of physics in that question which I hope have proved more interesting than the contents of can!