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The Perfect Amount of Ice to Keep Your Drinks Cold

by Kristin Conard Jul 6, 2011
It’s summer in the northern hemisphere, which often means lots of time outdoors – picnics, barbecues, and backyard or beach parties. And if you want to pop open a cold drink at any of these events, what do you need? Ice.

Over at WIRED, Rhett Allain has come up with the perfect amount of ice to keep your drinks at the ideal temperature. Because if you’re going to have the party, you may as well do it right.

But since it’s WIRED and the article written by an associate professor of physics, it isn’t a hit and miss, I think that looks about right guess on what you’ll need. Allain developed a scientific formula for your summer ice consumption needs. He (and readers) could just skip to the punch line, but that would take away from what I think are pretty impressive calculations (though probably wouldn’t be to any physics students) that took place to arrive at that answer.

He does the detailed calculating with some basic assumptions:

• Suppose you get n drinks and these start at room temperature. Let me say room temperature is 22 °C (about 72 °F)
• You start with ice and drinks. The ice is just at 0 °C.
• The cans are filled with water. I am actually surprised that canned water isn’t more popular. Why water? This is so I can use the specific heat capacity of water.
• How much water? Well, the standard size is 12 fl. This would be 355 ml or 355 grams of water.
• The can is aluminum and about 15 grams.
• The cooler has no mass. Yes, it is one of those massless coolers that you can get from the store. Also, the amount of energy transfer while the drinks are cooling is small.

From there, he uses constants, variables, graphs, formulas, specific heat, latent heat, etc. to come up with the answer: a 10 pound bag for a 12-pack in a worst case scenario of all the ice melting.

All his figures are just to determine the amount for drinks in cans. Determining the right amount for bottles would take a whole other set of figures.

Having drinks cold seems like it could be an indulgence in many places; if drinking water or water for crops and livestock is scarce, then using water to make ice to keep drinks cold is a luxury. But on the scale of ice and luxury, popping down to the supermarket for your 10 pound bag, like I would, is apparently still quite ordinary. There are lines of luxury ice like Névé or Gläce, where a single cube can cost $5, designed not, I suppose, to be used in coolers.

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