High School Physics : Enthalpy and Entropy

Study concepts, example questions & explanations for High School Physics

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Example Questions

Example Question #1 : Understanding Enthalpy

Enthalpy is a measure of __________.

Possible Answers:

the conversion of energy to heat

total energy lost in heat transfer

total work done by a thermodynamic system

total energy of a thermodynamic system

how easily something changes temperature

Correct answer:

total energy of a thermodynamic system

Explanation:

Enthalpy, or , is the total energy of a thermodynamic system. Similar to how mechanical energy can change during mechanical processes, involving changing distances of velocities, enthalpy will increase or decrease with changes made to the thermodynamic state of the system. It is simply a measure for a different form of energy.

Example Question #1 : Enthalpy And Entropy

An ice cube melts into water. While it is melting, what is the temperature of the mixture doing?

Possible Answers:

The temperature of the mixture steadily decreases while melting.

It remains constant while melting.

The temperature of the mixture steadily increases while melting.

The ice part of the mixture is colder than the water part.

The temperature fluctuates depending upon the point at which you measure it.

Correct answer:

It remains constant while melting.

Explanation:

When an object is changing forms (solid to liquid in this case), the temperature remains constant. All of the energy that would normally go towards changing the internal temperature of the object is going into  the latent heat of fusion or enthalpy of fusion instead.

Example Question #1 : Understanding Entropy

Entropy is a measure of __________.

Possible Answers:

change in heat

disorder within the system

specific heat

temperature

energy within the system

Correct answer:

disorder within the system

Explanation:

Entropy is the measurement of disorder within a system, or how far it is from thermal equilibrium. Remember that everything in nature tends towards an equilibrium. The further from that equilibrium something is, the more "disordered" it is when compared to nature's preferred state.

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