Cooling Bottles With ice Water

my friend and I work at a restaurant and we give the customers a big bottle of cold water for the table. We have these big bins that we keep the bottles cold in (and they are already cold since we pull them out of a fridge). I always just put ice in the bin and then the bottles. She argues with me that I have to put water in there as well. I feel that when you add water to it it melts the ice faster hence making the water warm faster. I even did a little experiment where I took 2 glasses and filled one with just ice and the other with ice and water. The one with the just ice had more ice in it then the one with ice and water. I know if you want to cool a warm bottle fast it is best to do ice and water (add salt for even faster). But I feel when you add the water to the ice yes it will feel colder....but very quickly the ice will melt and the water will warm. When you have just the ice it will take longer for the ice to melt so the bottles are kept cold longer.....plus the ice melts anyway creating that ice and water effect.... soooo.....any input on this argument?
- Joanna (age 41)
Baltimore, MD

Joanna- It sounds like you've figured it out. You've even done the experiment!

Here's a little explanation for our readers and for your friend. If the bottles need to be warmed up quickly, the water would help conduct heat away from them, just as you say. Adding salt causes the ice to melt faster, which pulls heat even more rapidly from the surroundings. Adding water to the ice won't hurt if the water is already at the freezing point, 0°C (32°F). If, however, you use warmer water, such as room-temperature water straight from the tap, it will by itself melt some of the ice. As you say, that will reduce the length of time that the ice will be around to keep things cold. It makes more sense for you to just to use plain ice.

Mike W.

(published on 06/10/2013)