# Worksheet: The First Law of Thermodynamics

In this worksheet, we will practice defining the first law of thermodynamics, which states that the total energy of an isolated system is constant.

Q1:

What is the first law of thermodynamics?

• AThe energy of a system always increases in any physical or chemical process.
• BThe energy of the universe (encompassing the system and the surroundings) is always conserved in any physical or chemical process.
• CThe entropy of a system always increases in any spontaneous process.
• DThe energy of a system always decreases in any physical or chemical process.

Q2:

Consider a cyclic process in which a system performs a net amount of work on its surroundings (i.e., corresponding to the net work done by the system). Would this process be endothermic , exothermic , or adiabatic with respect to the net heat exchange between system and surroundings? And what would be the relationship between and ?

• AEndothermic, with
• CEndothermic, with
• DExothermic, with

Q3:

What is the first law of thermodynamics?

• AThe force necessary to move an object is equal to its mass multiplied by its acceleration.
• BAn object will remain static or in motion unless acted on by an external force.
• CThe change in internal energy of a system is equal to the heat energy supplied to the system minus the work done by the system.
• DThe partial pressure of each component of a mixture of ideal gases is equal to its vapor pressure multiplied by its mole fraction.

Q4:

Which of the following statements is correct?

• AFor a closed system, can never have a negative value.
• BFor an adiabatic process in a closed system, must be zero.
• CFor a reversible process in a closed system, must be zero.
• DFor an adiabatic process in a closed system, cannot have a negative value.

Q5:

The density of ice, , at 273 K is 0.915 kg/dm3, and that of liquid water is 0.99987 kg/dm3. How much thermodynamic work must be done to melt 1.00 mol of ice at 1.00 bar pressure?