Chapter 9: Energy, Enthalpy, & Thermochemistry

Energy

The ability to do work or transfer heat

Work

Energy used to cause an object that has mass to move

( w = F*d = m**a\*d = kg(m/s^2) = J )

Heat

* Energy used to cause the temperature of an object to rise


* Flows from warmer to cooler objects
* Transferred through collision of particles

SI unit

* Joule (J)
* 1 J = 1 kg(m/s)^2

British unit

* calorie (cal)
* 1 cal = 4.184 J

Nutritional unit

* Calorie (kcal)
* 1 Cal = 1 kcal = 4.184 kJ = 4,184 J

Potential energy

Energy an object possess by virtue of its position or chemical composition

Separating two attracting objects will _________ their potential energy

Increase

Putting two two repelling objects together will _________ their potential energy

Increase

Kinetic energy

Energy that an object possesses by virtue of its ? ask Juliana

* KE = 1/2mv^2 = kg(m/s)^2 = J

Internal energy (U)

Total energy contained within a system

Factors of kinetic energy within U

* Translational motion, rotational motion, vibrational motion
* Collectively called **thermal energy**

Factors of potential energy within U

* Intermolecular and intramolecular forces of attraction, locations of atoms, and of bonds
* Collectively called **chemical energy**

First Law of Thermodynamics

* Conservation of energy
* Energy is neither created nor destroyed
* Energy can be converted from one form to another
* If the system loses energy, it must be gained by the surroundings, and vice versa
* ∆U = U_final - U_initial

System vs. Surroundings

* **System:** Molecules we want to study
* **Surroundings:** Everything else surrounding

Open system

Can gain or lose mass & energy across its boundary (human body)

Closed system

Can absorb or release energy, **but not mass**, across its boundary (light bulb)

Isolated system

Cannot exchange matter or energy with its surroundings (stoppered Thermos bottle)