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Matter and Energy

Matter and Energy. Drill. Define the following: State Process Fill in the blanks: Specific enthalpy is an ______ property. If 2kg of water has a specific volume of 0.3 m 3 /kg, it occupies _____ total space. Matter and Energy.

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Matter and Energy

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  1. Matter and Energy

  2. Drill Define the following: • State • Process Fill in the blanks: • Specific enthalpy is an ______ property. • If 2kg of water has a specific volume of 0.3 m3/kg, it occupies _____ total space.

  3. Matter and Energy Now let’s learn how the state of a system can change through energy transfer. So far we have learned a bit about systems and how we describe them using properties. Thermodynamics - study of systems and energy transfer System – what we choose to study; can be open or closed Boundary – separates system from surroundings Surroundings – everything outside of system • Property – a characteristic used to describe a system • Extensive – “the whole is the sum of the parts,” Mass, Volume, Energy • Intensive – “the whole is the same as each part,” Density, Temperature

  4. Matter and Energy Thermodynamics - “the study of systems and energy transfer” So what is energy and how can it affect systems? Piston & Cylinder What do you think will happen to the system if we add weights to the top of the piston? What do you think will happen to the system if we lit a match underneath the cylinder? What would happen to the system if we placed the piston-cylinder in an ice bath? In each case, the system would change because of an energy transfer…

  5. Matter and Energy Thermodynamics - “the study of systems and energy transfer” So what is energy and how can it affect systems? Energy In (Weights) Energy Out (Ice Bath) Energy In (Match) Piston & Cylinder Energy – the ability to do work or create heat Energy Transfer – occurs when energy moves in/out of a system

  6. Matter and Energy Thermodynamics - “the study of systems and energy transfer” So now we know that energy can be either work or heat and can go in/out of a system… Energy In (Weights) Energy Out (Ice Bath) Energy In (Match) Piston & Cylinder …but what are work and heat, really?

  7. Matter and Energy Thermodynamics - “the study of systems and energy transfer” Work (W) = a force acting over some distance Force Distance Travelled Block If we pushed a block, we would be doing work on it… Mechanical Work = Force x Distance = F x d

  8. Matter and Energy Thermodynamics - “the study of systems and energy transfer” Work = a force acting over some distance Force Distance Travelled Block How much work is done on the block by a 5N force acting over 3 meters? Mechanical Work = Force x Distance = F x d W = (5 N)(3 m) = 15 N-m = 15 J

  9. Matter and Energy Thermodynamics - “the study of systems and energy transfer” Mechanical work example: 40 N d = 3 m Block Mechanical Work = F x d Remember…only the component of the force that is parallel to the displacement does work. W = (40 N)(3 m) W = 120 N-m W = 120 J

  10. Matter and Energy Thermodynamics - “the study of systems and energy transfer” Mechanical work example: 40 N d = 3 m Block 30O Mechanical Work = F (cos)x d W = (40 N)(Cos 30O)(3 m) Remember…only the component of the force that is parallel to the displacement does work. W = 103.9 N-m W ≈ 104 J

  11. Matter and Energy Thermodynamics - “the study of systems and energy transfer” Heat (Q) – energy transfer caused by a temperature difference If we place a flame beneath a system, we would be adding heat to it…we could also remove heat by surrounding the system with an ice bath.

  12. Matter and Energy Thermodynamics - “the study of systems and energy transfer” Work and Heat can add/remove energy from a system, but what forms of energy do systems have? Systems can have Potential Energy, Kinetic Energy, or Internal Energy.

  13. Matter and Energy Thermodynamics - “the study of systems and energy transfer” Potential Energy (PE) The block to the right will fall because a force equal to its mass times the acceleration of gravity is acting on it… Height, h Block PE = mgh g = 9.8 m/s2

  14. Matter and Energy Thermodynamics - “the study of systems and energy transfer” Potential Energy Example: PE = mgh, where g = 9.8 m/s2 PE = (1.5 kg)(9.8 m/s2)(3 m) h = 3 m PE = 44.1 kg-m2/s2 Block Remember, 1 N = kg-m/s2 PE = 44.1 N-m PE = 44.1 J m = 1.5 kg

  15. Matter and Energy Thermodynamics - “the study of systems and energy transfer” Kinetic Energy (KE) Block If the block above moves with a velocity, V, then its kinetic energy is…

  16. Matter and Energy Thermodynamics - “the study of systems and energy transfer” Kinetic Energy Example: m = 2 kg V = 5 m/s If the block above moves with a velocity, V, then its kinetic energy is… Block

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