Laws Of Thermodynamics

Question 1

1st law

Answer 1

When a closed system is taken through a cycle, the net work delivered to the surroundings is proportional to the net heat taken from the surroundings. Energy cannot be created/ destroyed it can in,y be transformed from one form to another.
Starts from one state and return to this original state. Can only describe a thermodynamic state by its properties.
Non flow energy equation: Q-W= U2-U1.
ΣδQ~ΣδW

Question 2

Constant pressure

Answer 2

Pressure of a system remains constant during a transformation. Volume can change, work can be done. Constant volume= no work done

Question 3

1st law can be expressed as

Answer 3

Σ(δQ-δW)=0, in a closed cycle.
Can also be expressed as ΣQ- ΣW=0

Question 4

Internal energy U

Answer 4

Total energy contained within thermodynamic system, includes kinetic energy and potential energy from intermolecular forces.
In closed system, increase in internal energy= heat supplied+ work done ON system.
Internal energy is apart of the system and can be increased/ decreased by a change in state. It truly flows across the system boundary.

Question 5

At the boundary of system

Answer 5

Flow: movement of a force= work.

When the flow occurs as a result of a temperature difference= heat.

Question 6

Work and heat transfer

Answer 6

Q-W with respect to surroundings
Q+W with respect to system