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Energy

Energy. Definition. Energy is the ability to do work Work is done on an object whenever a force (push or pull) moves an object through a distance Work = Force x Distance. Forms of Energy. Mechanical energy –any energy possessed by macroscopic (visible) objects Two kinds of mechanical energy

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Energy

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  1. Energy

  2. Definition • Energy is the ability to do work • Work is done on an object whenever a force (push or pull) moves an object through a distance • Work = Force x Distance

  3. Forms of Energy • Mechanical energy –any energy possessed by macroscopic (visible) objects • Two kinds of mechanical energy Kinetic Energy Potential Energy

  4. Potential Energy • Stored energy that is available to do work at a later time

  5. Kinetic Energy • Energy of motion

  6. Unit of Energy • Joule (J) • Unit used to be the calorie (cal) • 1 cal = 4.19 J • How many joules is 1500 calories? • How many calories is 36 J?

  7. Conservation of Energy • Whatever changes occur in energy from one type to another, the total amount of energy remains constant • Energy cannot be created or destroyed

  8. Equivalence of Mass and Energy • Einstein found that matter and energy are related • Whenever there is a decrease in energy in a system, there is an increase in mass • Whenever mass increases, energy decreases

  9. New Conservation Law • Old conservation of matter and energy laws were combined • Law of Conservation of Mass and Energy – the total of mass and energy will remain constant in any reaction

  10. Energy in Reactions • In every change, there is a change in energy • Energy change usually more noticeable in chemical changes

  11. Exothermic • If reactants have more chemical energy than the products, then energy must be lost in reaction • This release in heat energy causes the substances to become hot • Chemical reactions that release heat are called EXOTHERMIC

  12. Endothermic Reactions • If products have more chemical energy than reactants, energy must be absorbed • The absorption of heat causes substances to feel cold • This is called an ENDOTHERMIC reaction

  13. Activation Energy • Even though some reactions are exothermic it may still require a little energy to start it off • This starting energy is called ACTIVATION ENERGY

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