Question

WHY AND HOW DOES THE LEVEL OF MILK RISES WHEN I IS BOILED

Answer 1

MILK CONTAINS 87 PERCENT WATER , 4 PERCENT PROTEIN AND 5 PERCENT LACTOSE [ MILK SUGAR ].WHEN WE BOIL THE MILK , HE FAT SUGAR PROTEINS AND MINERALS GET SEPARATED.SINCE THEY ARE LIGHTER THAN MILK THEY GET COLLECTED ON THE SURFACE IN THE FORM OF CREAM.DURING HEATING SOME AMOUNT OF WATER GETS CONVERTED INTO VAPOUR AND THE BUBBLES OF WATER VAPOUR RISE TO THE TOP BUT THE HEAT IS CONDUCTED AWAY BY THE LAYER OF WATER AND THE FAT DROPLETS THAT HAVE A HIGHER BOILING POINT THAN WATER. THE VAPOUR GETS TRAPPED IN THE CREAMY UPPER LAYER .AS THE MILK IS HEATED FURTHER , THE WATER VAPOUR EXPANDS AND THE THICK FOAM IS PRODUCED ON TOP. AS THE MILK IS BOILED CONTINUOUSLY , THE WATER WHICH BOILS AT 100 DEGREE CENTIGRADE PRODUCES MOR WATER VAPOUR  AND PRESSURE BUILDS UP IN THE BOILING MILK SO THAT THE VAPOUR PRESSURE RISES THE CREAMY LAYER.SO THE MILK PUSHES THE CREAMY LAYER OUT AND SPILLS.