Energy PDF

Preview

Summary

Random crap...

Description

Energy quiz study guide Definitions! Exothermic!(of a reaction or process) accompanied by the release of heat. Endothermic (of a reaction or process) accompanied by or requiring the absorption of heat.

Equations! Potential Energy Equation PE = mgh ex.) if height x 3, PE x 3 Kinetic Energy Equation KE = (1/2)mv^2 ex.) if velocity x 3, KE = 3^3 = 9 times larger (be careful with j vs. kj, etc.) If a 5500 Watt oven is on for 6 hours, then how many kilowatt-hours (kWh) of energy are used? If the power company charges $0.10 per kilowatt-hour (kWh), then how much did it cost (in dollars) to run the oven for the 6 hours in the problem above? - 5500 W/1000 = kW = 5.5 kW - 5.5 kW(6 hr) = 33 kWh --------------------------------$3.30 - kWh / 10 To find the total R value multiply the!inches of each type of!item times the thickness value and then add them all up!

If 600 g of water is heated from 5 C to 55 C, then what is the heat added in kilocalories (same as food calories) Q = ( m ) ( Cp ) ( T2 - T1 )! Q = ( 600 g ) ( 4.184 J / g - C deg ) ( 55 C - 5 C )! Q = 125520 J!! Q = ( 125520 J ) ( 1 kcal / 4184 J ) = 30 kcal or

kg x (1 kcal / kg C) x (the increase of degrees) C = kcal

Another method is to use the formula: Heat (kcal) = Mass of water (kg) x Temperature Increase (degrees C). Water! If 2.5 kg of water is heated from 10 ° C to 20 ° C, then what is the heat added in kcal (same as food calories)? (1 kcal raises the temperature of 1 kg of water by 1 degree Celsius.) 2.5 kg!(1kcal / kg C)!10 C = 25 kcal If you heated 3 kg of water using 30 kcal of energy, then what would be the temperature increase of the water (degrees C)? 30 kcal / 3 kg = 10 C Memorize these things about water - The liquid-to-vapor phase change of water requires more energy than the ice-to-liquid phase change. - The water phase with the highest heat capacity is liquid water.! - A water molecule is polar with a negative oxygen end and a positive hydrogen end. - The water phase with the smallest temperature increase when adding 10 kcal of heat is liquid water.! - The energy required to evaporate 1 kg of liquid water equals the energy released when 1 kg of water vapor condenses into liquid.

Ice has a lower density than liquid water and therefore sinks. highest energy change=condensation of water vapor lowest energy change=cooling of water vapor neither highest nor lowest energy change=cooling of liquid water In what order do the steps below occur for this process?! first:!cooling of water vapor!! second:!condensation of water vapor!! third:!cooling of liquid water! Photosynthesis!

Respiration Atmosphere

Light!

Green house gases Water vapor = 60% of natural greenhouse effect" Carbon dioxide (CO2) = 26%" Methane (CH4) + nitrous oxide (N2O) + ozone (O3) = 8%# co2 process#

power vs energy$#

• Important Power Values (k = kilo, M = mega, G = giga, T = tera) • • •

"Caveman" ~ 100 W, U.S. per capita ~ 10 kW, Windmill ~ 1 MW, Nuclear power plant ~ 1 GW Total U.S. ~ 3 TW, Total world ~ 15 TW

• U.S. energy consumption • •

Sectors: industrial, transportation, residential, commercial Sources: oil, coal, natural gas, nuclear, hydroelectric, etc.

• Types of Energy •

Kinetic, Gravitational Potential, Thermal, Electrical

POWER = RATE of energy consumption = energy per unit time Units of watts (1 W = 1 Joule/sec) or kilowatts (1 kW = 1 kJ / sec)! ! ENERGY = power × time

Units of kilowatt-hours (kWh) or kilojoules (kJ) 1 kWh = 3,600 kJ (see notes section on PPT slide for calculation)...