I’m not a huge natural science person, but I just wonder what the process of “transferring” temperature is from ice to drinks. And why does it happen fast?
In: Physics
It’s physics.
Two processes are happening:
* Heat goes from high temperature things to lower temperature things, until everything ends up with the same temperature. The heat energy that’s in hot objects basically “spreads around” to the colder objects, until everything has the same temperature.
* Ice stays at 0 degrees Celsius (32 degrees Fahrenheit) until the last bit of ice is melted. The ice absorbs heat from the hot liquid around it, but all that heat energy goes into melting the ice (loosening up the water molecules from the solid chunk of crystal ice to a loose liquid of molecules). The ice absorbs heat but does NOT increase in temperature. The drink loses heat energy and does decrease in temperature.
So that’s how ice cools drinks, the heat energy in the hot liquid goes into the ice and it’s “used” to melt the ice, and while there’s ice left, the temperature of the ice does NOT increase. Thus the temperature of the liquid is forced to decrease so that “everything has the same temperature”, and the liquid will feel cold to you.
The same process, by the way, happens with boiling water. Boiling water does not go above 100 Celsius (212 Fahrenheit) while it boils, the heat coming from the flame is used to boil the water (loosen the molecules to steam form instead of liquid form). This is why the fire that can char a barbecue steak to a burnt crisp does NOT do the same to the same piece of meat if it’s in a soup (in water). The boiling water forces the temperatures to not go over 100 Celsius, thus preventing the burning of the meat.
Ice has a lot of thermal capacity. It’s not so much that it’s significantly colder than the drink, but that its energy-absorbing capacity is locked away as “latent heat of fusion”. When you freeze water, it drops quickly to zero C, then hovers there for a while as the water changes to ice. Toi a casual observer, it looks like nothing is happening. When it melts, it takes the same amount of energy to change it back to water, which comes from the drink you want to cool.
The natural world is about balance. Technically the ice is not making the water colder. The water is making the ice warmer.
As temperature drops towards absolute zero (kelvins, and yes, Kelvin is more than a Star Trek timeline), the speed of the molecules decreases. As the speed slows, the molecules get closer together (compress) and it releases very little heat. When surrounded by warmer water/drink the heat released (the molecules are moving freely spending heat) by the water molecules is absorbed by the ice. The drink gets colder because it is losing heat to the ice.
We can get into more details explaining endothermic and exothermic reactions, but that would be beyond ELI5.
The atoms of hot things are moving fast while the atoms of slow things are moving slow. When one of the fast atoms of the hot thing bumps into one of the slow atoms of the cold thing, it transfers some of its energy from the hot atom to the cold atom. This slows down the hot atom, making it slower/colder and speeds up the cold atom making it faster/hotter.
So the ice melts and the drink gets colder.
One of the big laws of the universe is that heat flows from hot things to cold things around them until the (originally) hot and cold things reach roughly the same temperature. This is what is happening with your drink. Its heat is transferred to the ice, warming the ice and cooling your drink.
Temperature, is how we experience the average speed (vibration rather than zooming around) of the particles in a substance: the faster they are, the hotter they feel. Relative to the “drink molecules”, the ice molecules are slower. As they bang into each other some of the movement energy from the fast (hot) drink gets transferred to the ice. The drink slows down a bit and the ice speeds up a bit. When it is fast enough the ice changes to freely moving water.
Overall then, the average speed of the drink particles in the drink have slowed down and the drink feels colder than the drink was to start with but warmer than the ice was.
Temperatures tend to even out over time, i.e heat flows from hot to cold.
A drink at room temperature (say 20 degrees C) is significantly warmer than ice at 0 degrees C, this means that heat from the liquid will transfer into the ice until they are equilibrium.
If you used something like a cold whiskey stone this would decrease the temperature of the liquid and increase the temperature of the stone until they were the same. Ice is somewhat special in that it melts about 0 degrees C, this means it stays at 0 degrees until it has all melted so it is able to cool drinks considerably more than if it was just warming up without melting.
Radiation. If your drink is room temp and you put a freezing cold ice cube in it, it’ll radiate some of its heat into surrounding water. This will make the water cooler, but the ice cube will also get warmer. This causes it to get warm enough to go over the “frozen” threshold (32 F or 0 C). The ice then melts.
Temperatures always want to be in equilibrium, so when something cold touches something hot, the cold object steals heat from the hot object so they both can have the same temperature. In this case the cold ice absorbs the heat from the drink and that lowers it’s temperature. Another example is when you have a hot food, the air surrounding it is colder so it steals the heat from the food making it “cold”
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