Why does milk overflow when boiled but not water?

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In summary, milk and water behave differently when boiled because milk contains solids such as fat and protein which create a membrane-like film that traps steam and causes the milk to overflow. Water, on the other hand, does not have these solids and therefore does not form a film, allowing the bubbles of steam to escape without resistance. To prevent milk or other liquids from overflowing, one can put a metal spoon in the pot to deflect heat.
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aapar
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hi dear frns!
why milks boil n overflow although this phenomenon is not seen in case in water?
 
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Layman's guess: The solids in milk (fat, protein) give the bubbles more stability.
 
  • #3
Here is a pretty interesting answer to a pretty interesting question:

Milk is not a simple liquid — it contains tiny globules of fat and casein which are not dissolved but suspended in water. On heating milk, there occurs a separation of constituents and some elements like cream, being lighter, float up.

After some time, a membrane-like film containing cream and casein is formed. When milk begins to boil, the heat energy is used for the conversion of water into steam.

As a result, the pressure below the film increases suddenly and the rising bubbles of steam makes the milk overflow. On heating water, no such film is formed and the bubbles of steam formed by boiling escape easily without any resistance. Hence, water does not overflow
on boiling.

— Arun Syamal, Mumbai
http://timesofindia.indiatimes.com/...ed-but-water-does-not/articleshow/1973641.cms

Avoid milk or other liquid overflow: When boiling milk or other liquids, put a metal spoon in the pot. The metal deflects heat and will prevent the milk or other liquids from over flowing, saving you from sticky clean ups ...
http://www.sizzlingpots.com/toolbox/tips/168-prevent-milk-overflows.html
 
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1. Why does milk boil and overflow?

When milk is heated, the proteins and fats in the milk start to separate and form a layer on the surface. This layer traps the steam produced by the boiling milk, causing pressure to build up. Eventually, the pressure becomes too much and the milk overflows.

2. Can I prevent milk from boiling over?

Yes, there are a few ways to prevent milk from boiling over. One method is to add a small amount of vegetable oil to the pot before heating the milk. This creates a thin film on the surface that prevents the proteins from forming a layer. You can also try stirring the milk frequently while heating it or reducing the heat to a lower setting.

3. Is it safe to drink milk that has boiled over?

Yes, it is safe to drink milk that has boiled over. The only concern is that it may have a slightly burnt taste. However, as long as the milk is not visibly burnt or contaminated, it should be safe to consume.

4. Does the type of milk affect how much it boils over?

Yes, the type of milk can affect how much it boils over. Whole milk, which contains a higher percentage of fat, is more likely to boil over compared to skim milk. This is because the fat in the milk contributes to the formation of the protein layer on the surface.

5. Can I put a lid on the pot to prevent milk from boiling over?

No, putting a lid on the pot will not prevent milk from boiling over. In fact, it may even cause the milk to boil over more quickly. When the lid is on, the steam produced by the boiling milk cannot escape and increases the pressure inside the pot, leading to more overflow.

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