In Spain recently, in temperatures around 34掳C, the ice cubes in my drink took far longer to melt compared with at home, where it is much colder. Why the difference?
Guy Cox
Sydney, Australia
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The rate at which ice cubes melt depends on the temperature of the drink, not the ambient temperature. In my experience, Spanish cafes and bars keep their drinks very cold, which obviously makes sense when it is 34掳C (93掳F).
In England, on the other hand, drinks and mixers are often not refrigerated at all and just rely on ice cubes to cool them. No wonder the ice melts faster.
David Bortin
Whittier, California, US
We all know, of course, that the rain in Spain falls mainly on the plain 鈥� where it dissolves a lot of minerals, resulting in 鈥渉ard water鈥� coming to Spain鈥檚 taps. Does hard water make hard ice?
But seriously, the questioner鈥檚 observation isn鈥檛 from a well- controlled experiment; there are too many unspecified variables.
Ice forms from water at around 0掳C (32掳F), but that doesn鈥檛 mean that ice cubes are necessarily stored at that temperature; they are usually colder by amounts that can vary widely. The other ingredients in the drink, even if they turn out to be chemically identical in the UK and Spain, may well have been refrigerated at different temperatures.
There is often little correlation between the outdoor temperature reported in the news and the (usually indoor) air temperature where beverages are commonly consumed. Ice 鈥渃ubes鈥� are a non-standardised commodity that vary widely in size and shape; melting is a process that depends on the ratio of surface area to mass.
Drink recipes are likewise non-standardised. In fact, it is to be expected that the ice-to-liquid ratio would be positively correlated to the local air temperature at the time of preparation.
Cups and glassware, as well, can influence the heat exchange rate. Composition, insulation, capacity, shape and mass are among the factors that would need to be controlled.
Finally, 鈥渇ar longer鈥� is an unquantified and highly subjective measure of elapsed time, perhaps even more so when considering any holiday-related alcohol and relaxed mood.
To answer this question 鈥� or ask a new one 鈥� email lastword@newscientist.com.
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