Tea in Milk: Reasons for Floating Upwards

  • Context: High School 
  • Thread starter Thread starter springBreeze
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Discussion Overview

The discussion revolves around the phenomenon observed when cold milk is added to hot tea, specifically why the milk initially sinks and then floats upwards. Participants explore various explanations related to density, temperature, and fluid dynamics, with a focus on the interaction between the two liquids.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that the cold milk warms up and thus floats to the top due to the principle that warmer liquids are less dense.
  • Others argue that the milk did not warm up beyond the temperature of the tea, questioning the initial explanation.
  • One participant points out that fat in milk floats in water, which could contribute to the behavior observed.
  • Another participant proposes that the act of pouring the milk creates a circulatory system that helps bring the milk back up to the surface.
  • It is noted that while milk is slightly denser than water, it is not enough to keep it at the bottom, suggesting that similar liquids would behave in a comparable manner.
  • One participant mentions that mixing occurs due to the miscibility of milk and tea, along with convective-inertial flow contributing to the observed behavior.

Areas of Agreement / Disagreement

Participants express differing views on the reasons for the milk's behavior in tea, with no consensus reached on a single explanation. Multiple competing hypotheses remain under consideration.

Contextual Notes

Some assumptions about the temperatures of the liquids and the effects of pouring versus floating are not fully explored, leaving room for further investigation into the dynamics at play.

springBreeze
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While my friend was making a nice cup of British tea today, I noticed that when he put cold milk into the tea, it first sank but then almost immediately afterwards floated upwards. He thought it could be that the cold milk warmed up and hence floated to the top since warmer liquids are less dense. Is that the only reason or are there others?
 
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He added milk to tea ... shakes head ...
 
springBreeze said:
He thought it could be that the cold milk warmed up and hence floated to the top since warmer liquids are less dense.
Well, the milk didn't get warmer than the tea it was sitting in, now did it?

1] Fat floats in water.
2] Pouring a liquid into another liquids will tend to set up a circulatory system. bringing the milk back up top.
 
I am with Dave's 2 - I would bet mainly on circulation. Milk density is slightly higher than that of water, but not enough to stay on the bottom. Most likely any other liquid with density and viscosity similar to that of water will behave exactly the same way, milk is just easier to see.
 
mgb_phys said:
He added milk to tea ... shakes head ...

You have milk without tea:confused: Why?
 
mgb_phys said:
He added milk to tea ... shakes head ...

Echo that.
 
madmike159 said:
You have milk without tea:confused: Why?

Woops I ment tea without milk lol. disgusting
 
springBreeze said:
While my friend was making a nice cup of British tea today, I noticed that when he put cold milk into the tea, it first sank but then almost immediately afterwards floated upwards. He thought it could be that the cold milk warmed up and hence floated to the top since warmer liquids are less dense. Is that the only reason or are there others?

I'm sure part of the answer is becasue he *poured* it in, rather than floated it on (i.e. black and tans, pousse-cafe drinks, etc.). Then, because milk and tea are miscible, mixing ocurred along with whater convective-inertial flow ocurred.
 
Milk with Tea FOR THE WIN
 
  • #10
NoobixCube said:
Milk with Tea FOR THE WIN

Hell yea, were going of topic though.
 

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