Thermochemistry

EnergyIn this topic, we are interested in energy transfers

Types of energy

Definition: energy is the capacity to do workKinetic energy

Energy produced by a moving object

Potential energy

Energy available due to objects position

Radiant energy

Solar energy

Chemical energy

Energy stored within chemical substances

Thermal energy

Energy associated with the random motion of particles and atoms

We are interested in thermal energy for this topic

Conservation of Energy

Different forms of energy can be converted into other forms of energy

For example: a ball rolling down a hill converts its potential energy into kinetic energy.

Through careful analysis, scientists have determined that the total energy of a system must be conserved.

This means that energy cannot be created or destroyed by any process. But energy can be interconverted from one form to another.

This also means that the energy of the universe must be held constant.

Thermochemistry

Thermochemistry is the study of heat change in chemical reactions.

Heat is the transfer of thermal energy between two bodies that are at different temperatures.

To use thermochemistry we need to define our system and surroundings.

The system is the part of the universe we are interested in studying.

The system can be open, closed, or isolated.

An open system allows for mass and energy to transfer.

A closed system allows for energy to transfer but not mass.

An isolated system will not allow mass nor energy to transfer.

The surroundings are everything else.

Chemical processes

A chemical process can be either endothermic or exothermic.

An endothermic process is a process in which heat has to be supplied to the system in order for the reaction to proceed.An exothermic process is a process in which heat is released by the system when the reaction proceeds.

Thermodynamics

Thermochemistry is a subtopic in the much broader area of thermodynamics.

Thermodynamics is interested in studying changes in the state of a system.

States of a system are the values for all of the relevant macroscopic properties

Examples: composition, energy, temperature, pressure, and volume.

Thermodynamics is governed by four laws.For our topic though, we are only interested in the first law

The First LawThe first law of thermodynamics is basically a restatement of the conservation of mass.

States that the energy gained or given off by the system must be absorbed or given off to the surroundings.Can be rewritten to give ΔE=q + w.

q is the symbol for the heat

q=msΔT

m is mass

s is specific heat

ΔT is the change in temperature

w is the symbol for work

w=F x d

F is the force and d is the distance that force is applied

For next time

We will talk about enthalpy changesHow to calculate them

What they stand for

CalorimetryConstant volume

Constant pressure

What each of these calculate