Thermochemistry Definitions

Question 1

Thermochemistry

Answer 1

The study of the energy changes that accompany physical or chemical changes

Question 2

Chemical system

Answer 2

A group of reactants and products being studied

Question 3

Energy

Answer 3

The ability to do work; SI units joules (J)

Question 4

Work

Answer 4

The amount of energy transferred by a force over a distance; SI units joules (J)

Question 5

Heat

Answer 5

The transfer of thermal energy from a warm object to a cooler object

Question 6

Temperature

Answer 6

A measure of the average kinetic energy of entities in a substance

Question 7

Potential Energy

Answer 7

The energy of a body or system due to its position or composition

Question 8

Kinetic Energy

Answer 8

The energy of an object due to its motion

Question 9

Standard State

Answer 9

The most stable form of a substance under standard conditions, 25 degrees and 100 kPa

Question 10

Standard Enthalpy of Formation (ΔHf0)

Answer 10

energy associated with 1 mole, formed from its elements in standard states

Question 11

Open System

Answer 11

a system in which both matter and energy are free to enter and leave the system

Question 12

Potential Energy Diagram

Answer 12

A graphical representation of the energy transferred during a physical or a chemical change

Question 13

Bond Dissociation Energy

Answer 13

The energy required to break a given chemical bond

Question 14

Molar Enthalpy Change (ΔHx)

Answer 14

The enthalpy change associated with a physical, chemical, or nuclear change involving 1 mol of a substance; SI units J/mol

Question 15

Endothermic

Answer 15

absorbing energy from the surroundings

Question 16

Closed System

Answer 16

a system in which energy can enter or leave, but matter cannot

Question 17

Surroundings

Answer 17

all matter that is not part of the system

Question 18

Enthalpy Change (ΔH)

Answer 18

The energy released to or absorbed from the surroundings during a chemical or physical change

Question 19

Calorimeter

Answer 19

a device that is used to measure thermal energy changes in a chemical or physical change

Question 20

Isolated System

Answer 20

an ideal system in which neither matter nor energy can move in or out

Question 21

Calorimetry

Answer 21

the experimental process of measuring the thermal energy change in a chemical or physical change

Question 22

Exothermic

Answer 22

Releasing energy to the surroundings

Question 23

Thermal Energy

Answer 23

The total quantity of kinetic and potential energy in a substance

Question 24

Law of Conservation of Energy

Answer 24

Energy cannot be created or destroyed

Question 25

Hess’s Law

Answer 25

The enthalpy change for the conversion of reactants to products is the same whether the conversion occurs in one step or several steps

Question 26

Exothermic Reaction example

Answer 26

Exothermic reaction is where energy is released into the surroundings as indicated by the lower level in the diagram. An example of an exothermic reaction is the burning of a candle where the bonds between hydrocarbons are broken releasing energy as heat into the surroundings

Question 27

Endothermic Reaction example

Answer 27

Endothermic reaction is when energy is absorbed from the surroundings indicated by the higher energy level. An example is cooking an egg where the pan absorbs the heat from the stove to begin cooking the egg

Question 28

Exothermic Chemical reaction example

Answer 28

An example of an exothermic chemical reaction is the combustion of magnesium where the product of the chemical reaction is magnesium oxide as energy is released into the surroundings through the combustion

Question 29

Endothermic Chemical reaction example

Answer 29

An example of an endothermic chemical reaction is the decomposition of water into its elements of hydrogen and oxygen