History of Energy
• How much energy did we need before the bronze age?
• How much energy did we need before the industrial revolution?
• How much energy do we need now?
• How much energy will we need in the future?
The 1st law of Thermodynamics
• The increase in the internal energy of a thermodynamic system is equal to the amount of heat energy added to the system minus the work done by the system on the surroundings.
• Heat is a process by which energy is added to a system or lost to a sink.
• Energy is lost to a system by doing mechanical work.
• Energy is always conserved between a system and its surroundings.
Law of Conservation of Energy
• Energy is Neither Created nor Destroyed
– Enthalpy: H = U + pV
– H is the enthalpy– U is the internal energy – p is the pressure of the system – V is the volume
– Entropy: S = k log W
– W is the number of microstates corresponding to a given macrostate– K is Boltzmann’s Constant
• Open Systems and Closed Systems
– The Universe is the Only Closed System in Nature
The 2nd Law of Thermodynamics
• In an isolated system, a process can occur only if it increases the total entropy of the system.
• Heat cannot spontaneously flow from a material at lower temperature to a material at higher temperature.
• It is impossible to convert heat completely into work.
Energy Conversion
• Any form of energy can be transformed into any other form
• Energy is the Ability to Do Work
Thermodynamics• Thermal Energy
– The internal energy of a system associated with kinetic energies of the molecules:
• molecular translation, • rotation, and • vibration• electron translation and spin • nuclear spin
– and the phase of the system.
Heat and Temperature• Specific Heat
• Latent Heat
• Molecular Kinetic Energy
• Temperature Scales– Fahrenheit– Celsius– Kelvin
• Absolute Zero
Heat Budgets
Heat Budget of the Atmosphere and Ocean: QT = QSW + QLW + QS + QL + QV
Thermoregulation
Quiz• 1. T or F, energy is the ability to do work.
• 2. T or F, any form of energy can be converted to any other form of energy.
• 3. Simple machines make work easier, but less efficient. Name a simple machine.
• 4. T or F, photons can cause electrons to flow through a circuit.
• 5. T or F, zero-point energy is a viable alternative source of energy for the future.
Test Questions• Energy is the capacity to do work. Potential Energy = the potential to do work. Kinetic Energy =
the energy of motion (momentum).
• Any form of energy can be converted to any other form of energy. All energy can be accounted for in a closed system (in other words, energy is conserved). Entropy describes the total energy of a system and tells us that we cannot get more energy out of a system than we put into it.
• W = Fd; Power = W / t; Simple Machines make work easier by changing the distance through which force is applied.
• Thermal energy is the internal and external energy of atoms. Heat is the transfer of thermal of energy between atoms. Temperature is a measurement of the kinetic energy of molecules.
• Adding heat energy to substances makes their temperature rise (specific heat). To change the state of a substance requires even more heat energy (latent heat).
• Heat can be transferred by radiation, conduction, and convection.
• Organisms transfer energy through trophic chains. The higher you are on the food chain, the less efficient you are in converting the energy contained in your food into work (activity; yes, thinking is activity).