Question

An unknown liquid at a high temperature is safely mixed with normal water until an equilibrium temperature is reached. Some heat is gained by the cold water. Identify by which of the following law this can be explained ?

• A. First law of thermodynamics (conservation of energy)
• B. Second law of thermodynamics (law of entropy)
• C. Ideal gas law
• D. Heat of fusion and heat of vaporization equation
• E. Heat engine efficiency

Answer 1

The correct option is A First law of thermodynamics (conservation of energy)

According to the law of conservation of energy, the total energy of the system would remain the same.
On addition of hot liquid into the normal water, the hot liquid lost heat energy in order to achieve the equilibrium temperature. The same amount of heat is absorbed by the water to raise its temperature to the equilibrium level.