Matter and Energy

Drill

Complete the following equations:1) KE = 2) = m g h3) = F d4) Compression Work (isobaric) =

Matter and EnergyProperty – a characteristic used to describe a

systemState – a list of all the property values of a systemProcess– a record of all the states that a system passes through

1 2 3

4 5 6State

Process

Matter and Energy

Energy can go into or out of a system as either work or heat …so far we’ve covered:

Thermodynamics - “the study of systems and energy transfer”

Work:• Mechanical Work = F x d• Expansion/Compression Work =

isobaric if ,)( 12

2

1

VVPPdVV

V

Energy:• Potential Energy (PE) = m g h• Kinetic Energy (KE) =

But what about the energy that is inside a substance?

2

2

1mV

Matter and Energy

Internal Energy (U) =

Thermodynamics - “the study of systems and energy transfer”

The energy that is stored within a substance at the molecular or atomic scale due to its arrangements or movements The chemical energy that is stored within a substance such as in a batteryAny nuclear energy that is stored within a substance

+

+

Any energy associated with a substance that is not bulk kinetic or potential energy…

Matter and Energy

Energy can go into or out of a system as either work or heat …so far we’ve covered:

Thermodynamics - “the study of systems and energy transfer”

Work:• Mechanical Work = F x d• Expansion/Compression Work =

isobaric if ,)( 12

2

1

VVPPdVV

V

Energy, (E):• Potential Energy (PE) = m g h• Kinetic Energy (KE) = • Internal Energy (U)

2

2

1mV

Heat:• Heat (Q)

But how are these things all related? To answer that, we must introduce the 1st Law of Thermodynamics

} E = PE + KE

+ U

Matter and Energy

1st Law of Thermodynamics:

Thermodynamics - “the study of systems and energy transfer”

“Energy can be neither created nor destroyed, only transformed.”

“Any change in the energy of a closed system must be caused by either work or heat.”

or…

or…

121212 W- Q E

Matter and Energy

1st Law of Thermodynamics:

Thermodynamics - “the study of systems and energy transfer”

2-12-12-1 W- Q E The subscripts “1-2” should be read as “1 to 2” and refer to a change in the state of the system from State 1 to State 2.

2-1W

2-1QState 1

State 2

Adding heat or work to a closed system changes the energy stored in the system; it changes the state of that system.

What is the term that describes a change in the state of a system?Process

Matter and Energy

1st Law of Thermodynamics:

Thermodynamics - “the study of systems and energy transfer”

2-12-12-1 W- Q E This equation shows how work, heat and energy are related…it doesn’t determine the direction!!! Work and heat can enter or leave a system, and there is a sign convention that is used to show their direction.

Matter and Energy

1st Law of Thermodynamics:

Thermodynamics - “the study of systems and energy transfer”

2-12-12-1 W- Q E

Sign Convention:

Heat Transfer, (Q)• Heat in is positive (+)• Heat out is negative (-)

Work, (W)• Work in is negative (-)• Work out is positive (+)

Matter and Energy

1st Law example:

Thermodynamics - “the study of systems and energy transfer”

A piston cylinder containing a fluid is compressed while being cooled. If the work done is 5090 kJ and the heat removed is 1500 kJ, what is the change in energy of the fluid?

2-1W

2-1Q

2-12-12-1 W- Q E kJ) (-5090 - kJ) (-1500 E 2-1

kJ 3590 E 2-1