1. The problem statement, all variables and given/known data I don't have a specific problem I'm trying to solve, I'm trying relate all the concepts for basic thermodynamics. I'm not entirely sure where I am misunderstanding 1. What is work 2. What is internal energy? 3. What is heat? 4. What is enthalpy? 5. What is entropy? 2. Relevant equations U (internal energy) = N(particles) * f (degrees of freedom) * 1/2 * k(boltz) * T(K) ΔU = Q(heat) + W(work) W = P(pressure)ΔV(change in V) W = ∫[vi→vf] p(v)dv W = PAΔx Cv = (ΔU/ΔT)V = Nfk/2 T CP = CV + R PV = NkT or PV = nRT ΔS = dQ/T Pv diagrams isothermal work = P1V1 ln (V1/V2) isobaricwork = W = P(V2 - 1) (k = 1.4) adiabatic work = P2V2 - P1V1 / 1 - k isochoric work = 0 3. The attempt at a solution 1. What is work? Force parallel to the distance something is accelerated w= F * D = N*M = J It is analogous to heat in that heat yields microscopic kinetic energy and work yields macroscopic kinetic energy. It can also be thought of as pressure (force)/(area) times the change in volume N/M^2 * M^3 = NM = J 2. What is internal energy? Internal energy is the work plus the heat of a gas. (ΔU = Q(heat) + W(work)) I don't understand this fully - a gas can have heat but work is not a quantity something contains like mass. To me the only way work can be related is by the change in work to the change in internal energy. More heat can be added for a state of less or more internal heat if work is done to or by the gas, resulting in a higher or lower temperature for the gas at some pressure. U thermal energy is defined as the Nk(boltz constant * number of molecules) * degrees of freedom / 2 * (Temperature in kelvin) U = NkFT/2 F changes as the temperature of a gas increases, at STP it is usually 3 degrees of freedom. 3. What is heat? average kinetic energy of molecules in a substance - defined by Uinternal(equation directly above) can take forms of translational or rotational modes of energy - law of dulong petit says that for a solid it's just 3 translational modes. 4. What is enthalpy? defined as heat added at constant pressure. H = U + pv this confuses the crap out of me. U = Work +\- Q so. H = work + Q -\+ work so H is just Q? 5. What is entropy? equation is ΔS = dQ/T defined as "disorder", heat per unit temperature. Toss a hot iron bar at of some mass into an infinitely big ocean. Entropy increases because dQ1 = dQ 2 = dQ, but delta T is different. dQ / Thigher < dQ/ T lower so there is a net positive entropy.