I first noticed this with my mum and how pouring a cup of tea into another empty cup, then pouring it back into the first cup, and vice versa cools it down quite fast. Why?
FYI I am decently knowledgeable in heat transfer and thermodynamics
In: Physics
It’s all about increasing the surface area exposed to air when you pour the liquid between the cups. This helps the heat dissipate quickly, cooling down the beverage faster. Plus, the motion of pouring also increases mixing and contact with the cooler cup, aiding in the cooling process. Pretty neat, right? Enjoy your nicely cooled tea.
Besides the air cooling it down, the cup which is empty at the end will have an increased temperature once you are done (so this is where some of the heat went).
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