Matter and Energy

Drill December 15, in = __________cm 70 mph = __________km/s 5.5 yrs = __________ s

Matter and Energy This course is an introduction to the study of thermodynamics and an investigation of how it can be applied to renewable and non-renewable energy sources. Thermodynamics comes from the Greek words: therme (heat) + dynamis (force) = Thermodynamics “the study of systems and energy transfer”

Matter and Energy So what is a thermodynamic system? Thermodynamics - “the study of systems and energy transfer” Pressure Cooker Gas-fired Boiler Geothermal Power Plant System – whatever we choose to study Systems have a boundary and surroundings. We could be talking about…

Matter and Energy So what is a thermodynamic system? Thermodynamics - “the study of systems and energy transfer” We can choose to study all… System – what we choose to study Boundary – separates system from surroundings Surroundings – everything outside of system or some part… of a complex system. Always draw the system and its boundaries before starting any work!!!

Matter and Energy Let’s practice drawing system boundaries… Thermodynamics - “the study of systems and energy transfer” What’s the boundary if I’m interested in the pressure drop of steam as it passes through the turbine? What’s the boundary if we’re interested in the efficiency of the cooling tower? We’ve been asked to determine the efficiency of the entire geothermal power plant...what should our boundary be?

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”

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 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

HOMEWORK Define the following properties: Specific volume Density Specific gravity Humidity