Laws Regulating Energy ChemCom Notes

Laws Regulating Energy Also called the laws of Thermodynamics Zero Law – Energy Transfer First Law – Conservation of Energy Second Law – Entropy Third Law – Absolute Zero

Zero Law – Energy Transfer Energy will be transferred from areas of high temperature to areas of low temperature until the difference in temperature is zero. 25ºC 15ºC

First Law – Conservation of Energy Total energy in the universe is constant. Energy is never actually created or destroyed. It only changes from one form to another, or moves from one place to another, or is converted to mass.

Refresher Time Find someone else in class (not sitting in your seating group) who is wearing the same color as you are. Discuss the following questions and be ready to report out: What are three things that always make you laugh? What are two things you are afraid of? What is one thing you are good at doing?

Second Law - Entropy All things (mass and energy) tend toward disorder. So within any given system, energy will move from a state of organization toward a state of randomness. As disorder increases, energy changes into less usable forms. Because of this, any process that harnesses energy always loses some along the way-conversion can never be 100 percent efficient. 100%

Third Law – Absolute Zero Molecular movement stops at absolute zero (-273°C). Since temperature measures how fast molecules move, there can be no temperature lower than absolute zero.

Other Important Ideas Useful Energy Energy Efficiency

Useful Energy The desired output energy of an energy conversion. In an electric oven the input electric energy is consumed while the oven is on, and the useful output energy is the thermal energy used to bake or cook the food. Input Energy Useful Output Energy

Energy Efficiency No energy conversion is 100% efficient, but the energy is not lost. Energy is ALWAYS conserved but it is not always in a form that is useful. In science, energy efficient measures the ratio of useful output energy to input energy(Alberta Education). The debate regarding ethanol is a good example of a debate focused on energy efficiency.

Energy Efficiency Calculations Energy Efficiency is calculated by determining the amount of useful energy and dividing it by the input energy. Remember it cannot be 100% or more so that is a great way to check your math!

Energy Efficiency Example Information: A burner on a stove uses the equivalent of 200 therms of energy to heat the burner to the equivalent of 150 therms. Which is the useful energy? Which is the input energy? What is the energy efficiency?

Energy Efficiency Practice A Flashlight uses 55 units of energy to produce 12 units of light. What is the efficiency of the flashlight? A outdoor grill in the winter time uses 1,905 units of energy to produce the heat needed (245 units of energy) to cook a burger. How efficient is this?