• Question: If heat flows into colder areas, how can I feel the cold coming out of a Coke can?

    Asked by anon-177347 to Urslaan, Nicola, Helen, Daniel, Becky, Andrew on 9 Jun 2018.
    • Photo: Urslaan Chohan

      Urslaan Chohan answered on 9 Jun 2018:

      Your hand is warm relative to the can, so actually heat from your hand is going into the can! But this is more of a biology question. In our skin we have heat receptors, which send signals to our brain. When we touch something that is warm relative to the temperature of our body, they send a signal that something is hot. If it is cold relative to body temperature, they send a signal that it is cold. If it is too hot or cold, the brain responds “ouch, let go!”

    • Photo: Daniel Marsh

      Daniel Marsh answered on 9 Jun 2018:

      The coke can contains a carbonated drink (carbon dioxide is dissolved in the liquid under pressure), that means that the air inside the can is under higher pressure than the ambient air outside so when you open it up it equalises the pressures by expelling the cold air and this is why you get that little hiss as the pressure is released and the cold air is propelled into the warmer air.

    • Photo: Andrew Singer

      Andrew Singer answered on 9 Jun 2018:

      You can look at this question as being the result of three events going on at the same time:
      1) The way I like to think about it: the cold from a can of soda is sucking out the heat from the surrounding warmer air. Assuming you just took your can out of the fridge when you do this experiment, as your hand gets closer to the can you’ll start to feel this gradient from hot to cold. If you leave the can there for an hour, it’ll likely have no temperature gradient as the can only suck out heat from the air until it is the same temperature as the air–at which point they are at equilibrium.
      2) The can contains fizz (carbonation) which is constantly being released into the air. This cold gas leaves the can and starts to fill the air surrounding the can with the cold air. Eventually, the soda will go flat, which is when the carbonation is gone.

      To know how much the fizz influences the cold you feel is to try this experiment with fizzy and flat soda! Tell me how it goes!

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