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 Megan_5942 #1 Posted : Wednesday, June 16, 2021 10:17:55 PM Rank: NewbieGroups: Registered Joined: 5/12/2021Posts: 1Thanks: 0 timesWas thanked: 0 time(s) in 0 post(s) What exactly is the difference between internal energy and enthalpy? In my text I see it says enthalpy is equal to heat in closed systems (which makes sense) but enthalpy equals internal energy in solids/liquids. But they act so similar I don't even know what this means (bc they have similar formulas). Any help in distinguishing would be appreciated! Back to top User Profile
 INSTR_Calla_139 #2 Posted : Thursday, June 17, 2021 4:53:44 PM Rank: MemberGroups: Registered Joined: 6/8/2021Posts: 13Thanks: 0 timesWas thanked: 0 time(s) in 0 post(s) Hello,I am going to start out with some quick definitions for you:"Internal energy (E, sometimes U) is the sum of all the kinetic and potential energy in a system.It is difficult to measure an absolute value for the internal energy of a system, so we are onlyinterested in determining the change in internal energy of a system""Enthalpy (H) is the total energy transferred during a chemical process, including both the changein internal energy of the system (E) plus any energy (work) that is required to make room withinthe surroundings for the products of the reaction. Enthalpy is energy and therefore has units ofJoules."So knowing these definitions lets take a look at this equation:ΔH = ΔE + Δ(PV)ΔH - change in enthalpyΔE - change in internal energyΔ(PV) - change in pressure x volumeyour question asked how internal energy equals internal energy in solids and liquids. this is because in solids and liquids the pressure and volume stay constant so in this case ΔH = ΔE. I recommend skimming the chem. cc lesson 4 (thermodynamics) ~pg.194 Back to top User Profile
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