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Why Do Things Happen?

Why Do Things Happen?. Objectives. To understand the importance and general properties of energy To understand the concepts of temperature and heat To understand the direction of energy flow as heat.

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Why Do Things Happen?

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  1. Why Do Things Happen?

  2. Objectives • To understand the importance and general properties of energy • To understand the concepts of temperature and heat • To understand the direction of energy flow as heat

  3. Energy is the driver of all changes. It flows between objects, it spreads out throughout the universe and in doing so is the driver of all observable phenomena (including chemical reactions) What is Energy? Kinetic, potential, thermal, gravitational, sound, elastic, light / electromagnetic, electrical, electrostatic energies are examples

  4. A. The Nature of Energy • Energy is the ability to do work or produce heat. Doing Work: Producing Heat: Crane Lifting Explosion

  5. What is the difference between potential and kinetic energy?

  6. A. The Nature of Energy • Energy is the ability to do work or produce heat. Kinetic energy Energy of motion E = ½ mv2 Potential energy Energy of position

  7. A. The Nature of Energy • Law of conservation of energy • Energy can be converted from one form to another but can neither be created nor destroyed. Bounce Ball Into Space

  8. A. The Nature of Energy • Law of conservation of energy in a chemical reaction • Energy can be converted from one form to another but can neither be created or destroyed. • Stored chemical energy of reactants is equal to energy of products plus energy given off • Some of the stored chemical energy of methane and oxygen is converted to heat as they react

  9. B. Temperature and Heat • Temperature is a measure of the random motions (kinetic energy) of the components of a substance. Fast Slow Hot water Cold water (90. oC) (10. oC)

  10. Measuring Temperature

  11. B. Temperature and Heat • Heat transfer is a flow of energy between two objects due to a temperature difference between the objects. • Heat transfer is the way in which thermal energy is moved from a hot object to a colder object. Hot water Cold water (90. oC) (10. oC) Water Water (50. oC) (50. oC)

  12. Heat Transfer The transition of thermal energy from a hotter to a cooler body • Radiation • Conduction • Convection • (Phase Change)

  13. C. Exothermic and Endothermic Processes • System – part of the universe on which we focus attention • Surroundings – everything else in the universe Look at the example of burning a match:

  14. C. Exothermic and Endothermic Processes • Exothermic – heat energy flows out of the system • Endothermic – heat energy flows into the system

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