MegaSack DRAW - This year's winner is user - rgwb
We will be in touch
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?
higher albedo value?
thicker?
more froth?
higher albedo value?
Albedo as I understand it should have no effect here.
Starting temperature's different?
It's 'cause they keep the milk in the fridge.
Hot water will be drawn closer to boiling, milk will be heated to around 65C
Have you measured the temperature? Perhaps it's just that milky drinks taste colder?
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
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
[url= http://www.engineeringtoolbox.com/specific-heat-fluids-d_151.html ]eng tool box[/url]
[url= http://www.clickandlearn.org/Physics/sph3u/heat.htm ]kids physics page[/url]
[url= http://www.dtic.mil/dtic/tr/fulltext/u2/747596.pdf ]crazy russians pdf[/url]
edit rhys got there before me...
Also wikepedia [url= http://en.wikipedia.org/wiki/Heat_capacity#Specific_heat_capacity ]on specific heat[/url]
toys that won't make a noticeable difference.
Froth insulates that's it.
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.
And an Americano will start at a way higher temperature.
Not really relevant but interesting none the less
[url= http://en.wikipedia.org/wiki/Mpemba_effect ]The Mpemba effect[/url]
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.
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.
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...
