In a bath 30kg of cold water at 20 degrees centigrade is added to 10kg of water at 60kg What is the temperature of the water Please explain in simple terms?

Answer 1

The 60kg in the above statement should be 60 degrees centigrade.

It is common to use the term Celsius instead of centigrade.

The First Law of Thermodynamics can be applied to the mixing of the cold water

and the hot water. They eventually come to thermal equilibrium at a temperature,

TE.

Q = ( Delta UCW ) + ( DELTA UHW ) + WB

Assume perfect insulation. -----> Q ~ 0.0

There is no work for the mixing. ---> WB = 0.0

Delta UCW = ( mCW ) ( CVCW ) ( TE - TCW1 )

Delta UCW = ( 30 ) ( 4.18 ) ( TE - 20 )

Delta UHW = ( 10 ) ( 4.18 ) ( TE - 60 )

Delta UCW = - ( Delta UHW )

( 30 ) ( 4.18 ) ( TE - 20 ) = ( 10 ) ( 4.18 ) ( 60 - TE )

30TE - 600 = 600 - 10TE

40TE = 1200

TE = 30 deg C <---------------------

The cold water gained internal energy from the hot water.

The hot water lost internal energy to the cold water.