Matter and Energy

Drill

Fill in the blanks: “Dynamis” is Greek for ________.

Define the following: Thermodynamics System Property

Matter and Energy

Specific volume: is the total volume of a substance divided by the total mass of that substance. .. Units ?

Matter and Energy

Density: is the total mass of a substance divided by the total volume occupied by that substance… Units?

Matter and Energy

Specific gravity: is the measure of the relative density of water at a standard temperature. For engineers we use the temperature of 60deg. F

Matter and Energy

Humidity: is the amount of moisture (water vapor) in the air. It can be expressed as absolute or relative humidity. Absolute humidity is the mass of water vapor divided by a unit of volume of air (g of water/ cm3 of air. Relative humidity is expressed as a %.

Matter and Energy

There are two types of systems…Closed Systems – no mass crosses the boundary

Open Systems – mass crosses the boundary

Thermodynamics - “the study of systems and energy transfer”

“Energy can cross the boundary of both open and closed systems.”

Matter and Energy

There are two types of systems…Closed Systems – no mass crosses the boundaryOpen Systems – mass crosses the boundary

Thermodynamics - “the study of systems and energy transfer”

“Energy can cross the boundary of both open and closed systems.”

Energy in… Energy out…

Matter and Energy

How do we describe systems?Thermodynamics - “the study of systems and energy

transfer”

Energy in… Energy out…

Property – a characteristic used to describe a system

What are some properties we could use to describe the system above?

MassVolume

MassVolume

TemperaturePressure

TemperaturePressure

We’ve intentionally placed the properties above into two groups. Why do you think that is?

What’s common to the properties in each group? How would you measure each property?If we removed a small amount of mass from the system, which properties would you expect to change?

Matter and Energy

There are two types of properties:Property – a characteristic used to describe a

system

1) Extensive – the whole equals the sum of its parts

Which set of properties are best described as extensive?

MassVolume

MassVolume

TemperaturePressure

TemperaturePressure

2) Intensive – the whole is the same as any partEXTENSIVE

INTENSIVE

Mass and Volume are both extensive properties.Temperature and Pressure are intensive properties.

Extensive properties usually use capital letters as symbols.Intensive properties usually use lower case letters as symbols.

Matter and EnergyProperty – a characteristic used to describe a

systemProperty Symbol

Definition

Mass m measure of the amount of material present

Volume V amount of space occupied by an object

Energy E the ability to do work or produce heat

Temperature

T measure of the molecular activity of a substance

Pressure P force exerted per unit area on the boundaries of a substance

Density ρ the total mass of a substance divided by the total volumeWhat type of property is

density, ρ?What type of property is energy, E?

IntensiveExtensive

Matter and EnergyProperty – a characteristic used to describe a

system

When an extensive property is made intensive by dividing by mass, we use a lowercase symbol and the prefix “specific”.

In general, an extensive property can be made intensive by dividing by the mass of the system.

Extensive Divide by Mass

Intensive

EnergyE

kilojoules, kJ

Energy/massE/m

kilojoules/kilogram

Specific Energye

kJ/kg

Matter and EnergyProperty – a characteristic used to describe a

system

When an extensive property is made intensive by dividing by mass, we use a lowercase symbol and the prefix “specific”.

In general, an extensive property can be made intensive by dividing by the mass of the system.

Extensive Divide by Mass

Intensive

EnergyE

kilojoules, kJ

Energy/massE/m

kilojoules/kilogram

Specific Energye

kJ/kg

Matter and Energy

Homework:Return the signed agreement form attached to your syllabus.Complete the handout you received in class

*Homework is due at the beginning of class!

Thermodynamics - “the study of systems and energy transfer”