Viewing 16 posts - 1 through 16 (of 16 total)
  • is it just me or does milk get colder quicker than water?
  • AnyExcuseToRide
    Free Member

    for example, when i buy a latte or a hot chocolate it seems to get colder waaay quicker than say a coffee just made with hot water like an americano?

    CaptJon
    Free Member

    higher albedo value?
    thicker?
    more froth?

    Spin
    Free Member

    higher albedo value?

    Albedo as I understand it should have no effect here.

    meddle
    Free Member

    Starting temperature’s different?

    ernie_lynch
    Free Member

    It’s ’cause they keep the milk in the fridge.

    djglover
    Free Member

    Hot water will be drawn closer to boiling, milk will be heated to around 65C

    oldnpastit
    Full Member

    Have you measured the temperature? Perhaps it’s just that milky drinks taste colder?

    rhys
    Free Member

    Isn’t the specific heat capacity of milk and air lower than that of water? Therefore will not require as much energy loss for a given temp drop

    toys19
    Free Member

    specific heat capacity of milk is 3.93 kj/kg.k water is 4.2, so it milk heats and cools faster than water.. (if the numbers for milk are correct)

    sources

    eng tool box
    kids physics page
    crazy russians pdf

    edit rhys got there before me…
    Also wikepedia on specific heat

    cynic-al
    Free Member

    toys that won’t make a noticeable difference.

    Froth insulates that’s it.

    ernie_lynch
    Free Member

    milk heats and cools faster than water

    Doesn’t it have to lose more heat and therefore take longer ?

    I reckon as c-al says, froth insulates. Plus water evaporates easier than milk and therefore loses heat quicker, so contrary to the OP’s observations, milk should take longer.

    cynic-al
    Free Member

    And an Americano will start at a way higher temperature.

    nick1962
    Free Member

    Not really relevant but interesting none the less
    The Mpemba effect

    toys19
    Free Member

    Al and others, your other cod physics might be right, I dunno, but if it heats faster it cools faster. Its got less energy.
    The heat in the system Q is equal to the mass x heat capacity x the temp change or Q=MxCpxDT

    so if the heat capacity is less, then there is less heat in the system. (the density of milk is just higher than the density of water, water is 1kg/l milk is 1.03kg/l)

    Assume its a litre
    Water at 85celcius heated from 15 =70 degree change
    Q=294 Kj
    Milk = 283 Kj

    So Al you might be right because if we assume the same cooling rate then every 4.042 kj lost is a degree lost for the milk, and 0.97 of a degree for the water.. It seems there is not much in it.

    cynic-al
    Free Member

    Yes toys but a 7% difference in SHC of say 15% of the drink ~ 1%

    Oops wrote that out before fully reading your post. Looks like my cod physics agrees with your non-cod physics.

    It just seems obvious that the insulating effect of the foam has to trump any SHC stuff, milk being ~95% water.

    toys19
    Free Member

    tbh its much harder to get a reasonable estimate by hand of the actual rate of heating and cooling, so I just went for the easy numbers…

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