Thermochemistry

What is energy?

The capacity to do work.

What is thermal energy?

The energy associated with the random motion of atoms and molecules.

What is chemical energy?

The energy stored within the bonds of chemical substances.

What is nuclear energy?

The energy stored within the collection of neutrons and protons in the atom.

What is electrical energy?

The energy associated with the flow of electrons.

What is potential energy?

The energy available by virtue of an object’s position.

What is heat?

The transfer of thermal energy between two bodies that are at different temperatures.

What is temperature?

The measure of thermal energy

What is different about temperature and thermal energy?

They are different because temperature is the measure of thermal energy.

What is thermochemistry?

The study of heat change in chemical reactions.

What is a system? What is around the system?

The specific part of the universe that is of interest in the study (in this case, it is the chemical reaction). Everything around the system is the surroundings.

Why would a bathtub of 40°C have more thermal energy than a mug of 90°C?

It has more thermal energy because of its mass. The amount of electrons and heat in the tub is greater than the mug.

Types of systems

Open, closed, and isolated.

What is exchanged in a open system?

Mass and energy

What is exchanged in a closed system?

Energy

What is exchanged in an isolated system?

Nothing

What is an exothermic process

Any process where heat is given off. Transfers thermal energy from system to surroundings.

What is a thermochemical equation

A balanced chemical equation plus an energy term.

What is an endothermic process?

Any process where heat is supplied to system from surroundings. Heat is applied to reaction.

Exothermic process equation

heat is a product

Endothermic process equation

heat is a reactant

What is enthalpy (H)

Enthalpy is used to quantify heat flow into or out of a system in a process that occurs at a constant pressure.

Change in heat equation

ΔH = H(products) - H(reactants)

ΔH = ?

= heat given off/absorbed during chemical reaction

Negative sign

Exothermic reaction

Positive sign

Endothermic reaction

What do stoichiometric coefficients refer to?

The number of moles in a substance

Reverse reactions means...

The sign of ΔH changes