General Chemistry Chapter 6

Radiant Energy

Energy provided by electromagnetic radiation

ex: the sun

Chemical Kinetics

The study of molecular dynamics in chemical reactions. How reactions take place

Chemical Thermodynamics

The study of energy and its transformations (heat and work). Energy related chemical reactions.

Thermal Energy

Energy associated with the random motion of atoms and molecules

Chemical Energy

Energy stored within the structural units of chemical substances

Internal Energy (E/U)

The capacity to do work or to transfer heat (electrical, thermal, chemical, etc.)

System

A limited, well defined part of the universe. Systems tend to attain the lowest energy possible

ex: water on the floor, bikes on a hill.

-processes that lower a systems energy tend to be spontaneous where processes that raise a systems energy tend to be non-spontaneous

Surroundings

Anything outside of the system being studied

Open System

A system that can exchange mass and energy with its surroundings

Closed System

A system that cannot exchange mass but can exchange energy with its surroundings

Isolated System

A system that cannot exchange mass or energy with its surroundings

Force (F)

To move something against a resistance. The change in momentum (P) per change in time.

P=mv

where:

m=mass

v=velocity

Heat (q)

The energy that is transferred from one object to another because of a difference in temperature. The transfer of thermal energy between two objects whose molecules/atoms have different average kinetic energies.

Zeroth Law of Thermodynamics

When two bodies are in thermal contact and allowed to read equilibrium they must have the same temperature.

or

Heat flows from hot to cold.

ex: ice water

1st Law of Thermodynamics

When energy is converted between forms, (KE and PE), energy is conserved.

Law of Conservation of Energy

The total quantity of energy in the universe is constant.

1st Law of Thermodynamics Equation

deltaE= q+w

where E=internal energy

q=heat

w=work

if;

q = (+), heat is absorbed by the system, endothermic

q = (-), heat is released by the system, exothermic

w = (+), work is done on the system.

w = (-), work is done by the system

Enthalpy, H

Heat flow in a system. Delta H is the change in enthalpy or heat of reaction.

Bond Breaking

Endothermic

Bond Making

Exothermic

Calorimetry

The measurement of heat flow (Delta H). Usually done with a calorimeter (an isolated thermal system, for example a styrofoam cup).

Heat Capacity

The amount of heat required to raise the temperature of an object by 1°C (1K).

J/°C

Molar Heat Capacity (C)

The amount of heat required to raise the temperature of one mole of substance by 1°C (1K).

J/mol°C

Specified Heat Capacity (c)

The amount of heat required to raise the temperature of 1.000g of a substance by 1°C (1K).

Hess' Law

If a reaction is conducted in a series of steps, delta H for the reaction will be equal to the sum of the enthalpy changes (delta H) for the individual steps.

delta H is independent of the number of steps!

Hess's Law Addition of Chemical Equations

-write all reactants together on the left side of the new equation.

-write all products together on the right side of the new equation.

-cancel all items that are identical on both sides of the equation.