Laws of Thermodynamics Sections 7.1 & 7.2

Learning Objectives… Define energy Explain how energy is related to work and heat Give examples of potential energy and kinetic energy State the first and second law of thermodynamics Discuss how the laws of thermodynamics relate to organisms

Energy Energy = the capacity to cause change, the ability to rearrange matter Work energy is measured in kilojoules (kJ) Thermal energy (heat) is measured in kilocalories (kcal) How we usually measure energy stored in food

2 types of energy: Kinetic energy = energy of motion Ex. A person walking Heat = the kinetic energy of randomly moving particles Is unable to do work Potential energy = stored energy Is due to location or structure Ex. Chemical bonds in a molecule

Thermodynamics Thermodynamics = the study of energy First Law of Thermodynamics = energy cannot be created or destroyed, but it can change forms Known as “Conservation of Energy” The total energy in a system plus its surroundings doesn’t change Means organisms can NOT create energy Must capture energy from the environment and transform it into a usable form

Second Law of Thermodynamics = when energy changes forms, some energy is converted to heat & disperses into the surroundings No energy transfer is 100% efficient, some energy is always lost as heat! As a result, the total amount of entropy in the universe continually increases

Entropy = a measure of the amount randomness or disorder in a system Shown as the symbol “S” Usable energy has low entropy Heat has high entropy

Complex Life Forms & The 2nd Law of Thermodynamics As organisms grow & develop they become more organized & complex Is the 2nd law of thermodynamics wrong? 2nd law is still true because organisms can only maintain order with a constant input of energy As they become more ordered the universe around them becomes more random Happens because heat is released as organisms convert energy they obtain into a usable form