Acombination of 0.250 kg of water at 20.0°c, 0.400 kg of aluminum at 26.0°c, and 0.100 kg of copper at 100°c is mixed in an insulated container and allowed to come to thermal equilibrium. ignore any energy transfer to or from the container and determine;
a. the final temperature of the mixture.
b. the change in the entropy of the universe in this experiment.

Heat gained in a system can be calculated by multiplying the given mass to the specific heat capacity of the substance and the temperature difference. It is expressed as follows:

Heat = mC(T2-T1) 

When two objects are in contact, it should be that the heat lost is equal to what is gained by the other. From this, we can calculate things. We do as follows:

Heat gained = Heat lost

The specific heats of the substances are as follows:
specific heat water = 4.18 J/g°C 
specific heat Al = 0.900 J/g°C 
specific heat Cu = 0.386 J/g°C 

250 g (4.18)( T - 20.0) + 400 g (0.900) ( T - 26.0) + 100 g(0.386) ( T - 100)=0 

Solving for T,

T = 24.3 degrees Celsius