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 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.” 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? Mass Volume Temperature Pressure 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? Mass Volume Temperature Pressure 2) Intensive – the whole is the same as any part EXTENSIVEINTENSIVE 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 Energy Property – a characteristic used to describe a system PropertySymbolDefinition Massmmeasure of the amount of material present VolumeVamount of space occupied by an object EnergyEthe ability to do work or produce heat TemperatureTmeasure of the molecular activity of a substance PressurePforce exerted per unit area on the boundaries of a substance Density ρ the total mass of a substance divided by the total volume What type of property is density, ρ ? What type of property is energy, E? Intensive Extensive

Matter and Energy Property – 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. ExtensiveDivide by MassIntensive Energy E kilojoules, kJ Energy/mass E/m kilojoules/kilogram Specific Energy e 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”