**The four types of energy:**- Kinetic Energy
- Potential Energy
- Internal Energy
- Enthalpy

**The two types of energy transfer**- Heat
- Work
**The first law of thermodynamics****Specific Properties**

Explanation: This section prepares us for energy balances, much as we did for material balances. If you recall, material balances where not performed until chapter four. Before we could jump into doing material balances, we covered topics on units, pressure, temperature, and flow rates, to name a few. We were not prepared to solve material balance problems until we understood a few basic concepts and definitions. Similarly, this section introduces terminology, fundamental definitions and mathematical relationships required to perfom energy balances. |

Explanation: There are really three types of energy that we'll deal with often in chemical engineering: Kinetic Energy, E
_{K} = 0. That is, the system has kinetic energy, but that energy doesn't change as you move between two point unless the system has undergone a change in velocity: the change in kinetic energy is zero.
In the bulk of energy problems that you will deal with, that is, those in which there is a chemical reaction, a change of state, or substantial temperature change, the change in kinetic energy is very small (DE_{k} = 0).
_{p} = 0). Additionally, rarely does the system rise or fall substantially in the energy balance problems that you will perform for chemical engineering problems in this class, so you will find that the potential energy change is often negligable and set to zero. Finally, you will notice that you will only deal with potential energy due to gravity in this course. If any other source of potential energy relavent, such as electrical potential, or some other type, that will be clearly stated in the problem statement.
closed systems-
C
_{V}= the heat capacity at constant volume.
Here, there are two equations to find the specific internal energy using a term with a hat over it (U- It is assumed that U-hat has units of Energy/mass in the above equations, when the first formulas could be used. If U-hat has units of Energy/mole, of course, we would multiply the specific internal energy by moles (and not mass) to get the internal energy (using, for example, U = n * U-hat). It may be more correct to write U = (n or m) * U-hat. The key to getting this write is to pay attention to the units of the specific property. This of course applies to all specific properties (U-hat, H-hat, V-hat, etc.) and is probably a point that you are already familiar with. Temperature Change of a Solida change in temperature (effects a molecule's motion), a chemical reaction (breaking and making bonds), a change of state (change in intermolecular energy), or a substantial pressure change(under high pressures, our H_{2}0 molecule in our ice cube vibrates less).
open systems- C
_{p}= the heat capacity at constant pressure.
Here, the usage of the first -> fourth equations is analogous to scenarios for those equations for internal energy already explained above. However, the last equations describe the relationship between enthalpy and internal energy. Similar discussions given above in the internal energy section about flow rates and specific properties are applicable here. |

Explanation: There are two types of energy transfer, heat and work. There should be a clear distinction between these two types of energy transfer and the forms of energy just mentioned. Where kinetic, potential, and internal energy are all forms of energy, heat and work are energy vehicles that move energy from one place to another. They act to transport energy by carrying energy from the surroundings into the system or from the system to the surroundings. Further examples follow, but let me give you one now: First, we need to name the system and the surrounding. The system could be a pot of water, and let's say that it experiences an increase in temperature (an increase in internal energy). The system gets energy from the surroundings and we say that this energy is transported by heat.
where the first notation designates some quantity of heat transported, and the second tells how fast heat is being transported per time.
where the first expression designates the general work expression (units, Joule), the second designates work per time (units, Joule/second), and the third is the modified work expression that we will use for open systems, where the s subscript designates shaft work, such as work by a propeller (units, Joule/second). |

Explanation: "Energy is neither created nor destroyed." There are several other ways to say this, such as the energy of the universe is constant, or that energy doesn't appear spontaneously. That is, our cup of water doesn't increase its temperature sponaneously, but due to energy brought in from the surroundings via heat or work. This statement is what allows us to make the energy balances. Energy, like mass, is conserved. |

The last topic has to do with the way properties are given. In earlier sections, we determined that m stood for mass, and m
Explanation: Let me offer you a way to determine whether a property is an external or internal property - If the answer to the following question is yes, then the property is external (otherwise, it is an internal property): Does the property change if we go from one gram to a 100 grams for the substance? for example, determine whether the following properties are external or internal. mass (kg), temperature (K), volume (gallons), energy (joules), density (g/mL). The extensive properties listed here (those that change when we change the amount of substance) are: mass, volume, and energy. Now we understand how to categorize a certain property as extensive or intensive. Finally, note that any extensive property can be turned into an intensive property if it is divided by an amount. The resulting intensive property is called a specific property. For example, mass is an extensive property. If we divide mass by moles, we get an intensive property, namely, the molecular weight of a substance. We can divide an extensive property by either mass or an amount (such as moles) to turn it into an intensive property. The reason intensive and extensive properties are covered is to introduce specific properties because we will use them so much in energy balances. That is, many of the physical properties taken from the tables in energy balance problems are listed as specific properties. |

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