Energy and Chemical Reactions

Flashcards covering key concepts in energy, heat, thermochemistry, and chemical reactions.

What is energy?

The capacity for doing work or supplying heat

What is potential energy?

Energy that is stored

What is chemical potential energy?

Based on the structure of chemicals

What is kinetic energy?

Energy of motion

What is heat?

Energy that is transferred from one object or substance to another because of a difference in temperature between them

What is thermochemistry?

The study of energy changes that occur during chemical reactions and during changes in state

What are the units of heat?

Joules (J) and calories (c)

What is specific heat (heat capacity)?

The amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius

What is the formula for Heat (q)?

q = m x Cs x ΔT

What is calorimetry?

The measurement of the transfer of heat into or out of a system during a chemical reaction or physical process

What is a calorimeter?

An insulated container that is used to measure heat change

What is a system in thermodynamics?

The specific part of the universe in which we focus our attention

What are the surroundings?

Everything else outside the system

What is an exothermic reaction?

Heat is released by the system to the surroundings

What is an endothermic reaction?

Heat is absorbed by the system

What is bond energy?

Released when the bonds form; the same amount must be added to break them

What is a thermochemical equation?

A chemical equation that includes the enthalpy change of the reaction

What does ∆H represent?

Change in energy during a reaction

What does a positive ∆H indicate?

The reaction is endothermic (absorbs energy and feels cold)

What does a negative ∆H indicate?

The reaction is exothermic (releases energy and feels warm)

What is Hess’s Law?

Two or more thermochemical equations can be added together to give a final equation

What happens when you reverse a chemical equation according to Hess's Law?

Change the sign of ΔH

What happens if you multiply the equation by a whole number according to Hess's Law?

The ΔH also gets multiplied by that number

Why add up ΔH values in Hess’s Law?

To determine the ΔH for the overall reaction

How is stoichiometry related to thermochemical equations?

Can be applied to a balanced chemical equation to determine how much energy is absorbed or released during a reaction with specific amounts of chemicals