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9 .1 Energy

Explore the different forms of energy, thermodynamics, and chemical reactions. Learn about kinetic and potential energy, activation energy, and the laws of thermodynamics. Discover how energy is transferred and transformed in various systems.

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9 .1 Energy

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  1. 9.1 Energy

  2. Energy is simply defined as the ability to do ‘work’ or produce heat • Work (w) is the flow of energy acting over an object causing it to move • Heat (q) is the flow of energy due to a temperature difference

  3. There are many different types of energy, which can overlap with each other • Kinetic energy • Potential energy • Nuclear energy • Thermal energy • Law of conservation of energy states that energy can be converted from one form to another but can be neither created nor destroyed. Energy of the universe is constant. • Sound energy • Electric energy • Gravitational energy • Chemical energy

  4. Potential energy is energy due to position or composition • A large stone on top of a hill, a nerf blaster that is loaded, gasoline and glucose all have a lot of potential energy • The potential energy can be transferred into other forms of energy

  5. Kinetic energy is the energy of motion and depends on the mass and velocity of the object • All particles, even atoms, are in constant motion • Waterfall, race cars, wind blowing, and ‘temperature’ • Temperature is the measure of average KE

  6. Chemical energy is the potential energy found inside chemicals • When chemical bonds are broken, it absorbs energy • When chemical bonds are formed, it releases energy

  7. Are chemical bonds being formed or broken? • Exothermic reaction is when chemicals release energy to the surroundings • Fire burning • Endothermic reaction is when chemicals absorb energy from surroundings • Instant ice pack

  8. Activation Energy • Just like a match needs to be struck first, reactions needs a little “push” • Some initial energy is required for reactions to take place. • The amount of energy that is needed is called the activation energy

  9. Endothermic Reaction Exothermic Reaction Absorbs Energy Releases Energy Energy

  10. What happens to chemical reactions if the activation energy is high? Will the reaction speed up, slow down, or stay the same? • If activation energy is high, reactions will occur slowly • A Catalyst is a substance that speeds up chemical reactions by lowering activation energy.

  11. How do we measure energy? • Joule (J) and calorie (c) are units of energy • 4.184 J = 1 c, or 4184 J = 1 kilocal(C) • 100 J is required to keep a 100-Watt light bulb shining for one second • Your phone stores about 19,000 J • Your body needs about 10,000,000 J (2400 C) of energy per day

  12. Thermodynamics • Thermodynamics is the study of energy • Internal energy (E) of a system is the sum of kinetic and potential energies of everything in the system • It is pretty much impossible to find the total amount of E of a system, like finding the volume of the ocean

  13. But it is possible to find the change of E in a system, like if you pour a cup of water into the ocean, you know the volume of the ocean just increased by 1 cup. • The change in E is the flow of energy found in work and heat ΔE= q + w Δ= “change in”

  14. The change in energy (ΔE) can be positive or negative depending on your perspective (if you are on the receiving or giving end) • In thermodynamics, the perspective is always from the ‘system’

  15. Solid-liquid-gas phases • What happens to solid as it gains energy? • Solid turns into liquid (melting) • What happens to liquid as it gains energy? • Liquid turns in to gas (evaporating/boiling) • What happens to gas as it loses energy? • Gas turns into liquid (condensing) • What happens to liquid as it loses energy? • Liquid turns into solid (freezing)

  16. Water freezes at 0°C and boils at 100°C • If I have a cup of water at 22°C (room temperature), what happens to the water as energy is removed from the cup? • Obviously the temperature is going to lower, but as it hits 0°C, what happens to it? • Does it freeze right away? • Does the liquid instantly turn into ice? • Does the temperature keep dropping?

  17. As water is cooled, once it hits 0°C, its actually stops dropping in temperature for a while • Energy has to be removed from liquid particles in order for it to freeze, before the temperature can decrease • The energy removed when freezing a substance is called heat of fusion

  18. Same thing for boiling water • As you increase the temperature of water, it stays at 100°C for a while, before the liquid can turn into vapor to become hotter than 100°C • The energy required to boil a substance is called heat of vaporization

  19. What do the plateaus represent?

  20. Make today’s Lesson into a story. OR Design a Rube Goldberg machine. (label energy and use at least 7 different forms of energy) Color. Neat.

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