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Hari Dhanushkodi

on 30 April 2013

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Transcript of Energy

ENERGY Anirudh Kais Sid & Hari Heat and Enthalpy Resisting Energy Absorption and Reflection of Energy Electromagnetic Spectrum is a type of energy. It can be transferred by temperature differences. HEAT ENTHALPY Some things require HEAT energy. Bond breaking Bond formation HEAT ABSORPTION OBJECTS ABSORB ENERGY! ENTHALPY is the heat content of a system. In other words: ENTHALPY = Total energy of an object Photons (energy) + other factor values Kinetic Energy + Potential Energy Pressure & Volume Electrons on the object's surface absorb photons!
Object's electrons are excited!
Electrons jump up energy levels!
These electrons carry absorbed energy!
To become stable, electrons jump down energy levels.
This is the full process of absorbing energy! Why ENTHALPY? Why use instead of total energy!? ENTHALPY Endothermic Reaction Absorbs Heat Plants ABSORB energy in photosynthesis to create glucose and oxygen. Or when ice cubes absorb energy, melting them. REFLECTION Electrons Jump Energy Levels
and Return to Ground
State, Releasing Energy OBJECTS REFLECT ENERGY! Energy Energy Object's reflect energy they can't absorb Object's reflect energy when the frequency of the energy wave doesn't match their own Electrons aren't excited for long enough, so the energy is reflected off the object :( Exothermic Reaction Releases Heat Consists of different frequencies of electromagnetic radiation
We are most familiar with visible radiation, or light!
Each frequency releases different amounts of energy
For example, visible light releases radiant heat Like Making ice cubes, which releases energy Or a reaction of Na with Cl, which releases energy while yielding NaCl The Light Spectrum is that part of the Electromagnetic Spectrum that is visible to us Exothermic and Endothermic Reactions Δ Because enthalpy accounts for pressure and volume, it allows chemists to see the change in heat in a reaction. (Enthalpy change) Enthalpy Change H products - H reactants ∆H reaction = H products – H reactants

A + B C + D Products (H) Reactants (H) H = enthalpy A + energy B + C A + B C + energy vs REACTION TIME!!!! REACTION 1 Citric Acid + Baking Soda + Water + + Citric Acid Water Baking Soda Releases CO2 gas. More bonds broken, energy absorbed RESULT The ending solution was cold. The reaction was ENDOTHERMIC. SUNSCREEN PHYSICAL CHEMICAL vs Zinc Oxide Titanium Dioxide Physical blocks reflect UV radiation. Made of internal metals. Does not wear off as much as chemical blocks. Chemical blocks absorb UV rays. Wears off quicker than physical blocks. REACTION TIME!!!! REACTION 2 Hand-Warmers Iron in hand-warmers bond to Oxygen in Air, creating Iron Oxide. Bonds formed, energy released RESULT The hand-warmer became hot. The reaction was EXOTHERMIC. Hand-Warmers + 4 Fe Iron 3 O 2 Oxygen 2 Fe O 2 3 Iron (III) Oxide REACTION TIME!!!! REACTION 3 UV Light + Sunscreen Sunscreen is filled with electron absorbing elements.
These elements absorb the UV Light, blocking it from the paper RESULT The lotion absorbs the electron stream from the UV Light. The lotion blackens, which is shown on the bond paper. The lotion becomes BLACK. + UV Light Sunscreen Lotion REACTION TIME!!!! REACTION 4 Yeast + Hydrogen Peroxide + Washing Liquid Reaction forms bonds to release Oxygen gas, energy released RESULT Bonds are formed, energy is released. The reaction is EXOTHERMIC. + Yeast Hydrogen Peroxide + Dishwashing Liquid + What is SPF? SPF is the sun protection factor of a sunscreen lotion. Higher SPF Numbers block out higher percentages of UVB rays. Potential Energy Diagrams Works Cited "Chemical Kinetics." PCCL. N.p., n.d. Web. 27 Apr. 2013.

"Electromagnetic Spectrum." - Introduction. N.p., n.d. Web. 27 Apr. 2013.

"Energy & Thermochemistry: Heat or Enthalpy - Enthalpy vs. Energy." Energy & Thermochemistry: Heat or Enthalpy - Enthalpy vs. Energy. N.p., n.d. Web. 27 Apr. 2013.

"Exothermic Reactions." Exothermic Reactions. N.p., n.d. Web. 27 Apr. 2013.

"Flash Animations." Flash Animations. N.p., n.d. Web. 27 Apr. 2013.

"High SPF Sunscreens: Are They Better?" WebMD. WebMD, n.d. Web. 27 Apr. 2013.

"How To Create an Endothermic Chemical Reaction (Safe)." About.com Chemistry. N.p., n.d. Web. 27 Apr. 2013.

LeMay, H. Eugene. Prentice Hall Chemistry: Connections to Our Changing World. Needham, MA: Prentice Hall, 2002. Print.

"Light Absorption, Reflection, and Transmission." Light Absorption, Reflection, and Transmission. N.p., n.d. Web. 27 Apr. 2013.

"Potential Energy." Potential Energy. N.p., n.d. Web. 27 Apr. 2013.

"Science in Your Mittens: The Chemistry of Hand Warmers." LSNED. N.p., n.d. Web. 27 Apr. 2013.

"What Is UV Light?" WiseGEEK. N.p., n.d. Web. 27 Apr. 2013. What is Energy? Energy is the capacity of a physical system to do work. What are the different types of energy? Thermal Chemical Electrical Mechanical Energy can never be destroyed or created, only transferred. Ready for a Quiz? H O 2 2 + Yeast H O 2 2 + O 2
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