Unit 9-13 Thermo Chem

Question 1

Energy

Answer 1

The capacity to do work

Question 2

Potential energy

Answer 2

The ability an object has to do work because of its position or condition (Ep)

Question 3

Kinetic Energy

Answer 3

The ability an object has to do work by virtue of its motion (Ek)

Question 4

Potential energy is determined by…

Answer 4

The intermolecular bonds between the atoms in the molecule and the nuclear bonds within the nucleus of the atom. Separated molecules and atoms have the potential to form bonds, so atoms and molecules in the separated state can possess a greater potential energy relative to their combined state

Question 5

Kinetic Energy of matter is determined by…

Answer 5

The motion of the particles within the matter

as the motion of the particles increases the kinetic Energy increases

Question 6

Vibrational motion

Answer 6

An oscillation or back and forth motion of a particle in a confined space

Question 7

Rotational motion

Answer 7

Spinning of a particle about its axis or centre

Question 8

Translational motion

Answer 8

A straight line motion of a particle,

Question 9

Temperature

Answer 9

Is a relative measure of the average kinetic energy of (atoms, molecules,ions) in matter. As temperature increases, kinetic energy increases. If temperature remains constant, the kinetic energy of the matter remains constant

Question 10

Kinetic Energy at absolute 0

Answer 10

Particles will not have any kinetic Energy at Absolute Zero (0k), they will however still have potential energy

Question 11

Enthalpy

Answer 11

Every substance has a particular heat content, this heat content = enthalpy. Is the total internal energy of the substance and cannot be directly measured, measure the difference in energy between reactants and products in any reaction

Question 12

Enthalpy of reaction

Answer 12

The amount of energy gained or lost to the surroundings

Question 13

Heat of reaction

Answer 13

The change in enthalpy, represents the change in the total internal energy (KJ)

Question 14

Exothermic

Answer 14

If energy flows out of a system, the magnitude of that energy is accompanied by a negative sign indicating that the systems energy is decreasing. Surroundings heat up

Question 15

Endothermic

Answer 15

Energy flows into a system, the magnitude of the energy is accompanied by a positive sign indicating that the systems energy is increasing. Surrounds cool down

Question 16

Potential energy diagrams

Answer 16

Is labelled Ep on the y axis, and time or reaction coordinate on the x axis. Ep = kJ, the reaction proceeds in a forward direction as you follow along the Xaxis from left to right
Endothermic: “p” over r
Exothermic: r over p

Question 17

Melting or fusion

Answer 17

A change from a solid to a liquid

Question 18

Vaporization

Answer 18

A change from a liquid to a gas

Question 19

Sublimation

Answer 19

Change from a solid to a gas/gas to a solid

Question 20

Solidification or freezing

Answer 20

A change from a liquid to a solid

Question 21

Condensation

Answer 21

A change from a gas to a liquid

Question 22

Phase Change

Answer 22

The amount of Ep energy stored in the molecules changes, the amount of Ep in gas molecules is more compared to a liquid, which in turn is more than a solid. There is no change in temperature during a phase change, the incoming energy is used to break or build intermolecular bonds and is either stored or given off as heat

Question 23

Warming and cooling curve

Answer 23

This is a plot of temperature versus time for a process where energy is added at a constant rate. Kinetic and potential energy changes during the process of warming can be most easily represented

Question 24

Heat of fusion of ice

Answer 24

The energy change that occurs during the melting process

Question 25

Heat of vaporization of water

Answer 25

The energy change that occurs during the boiling process

Question 26

Specific heat capacity

Answer 26

The amount of heat energy required to change the temperature of one gram of the substance one degree celcius

Question 27

Heat capacity

Answer 27

The amount of heat required to raise a given quantity of a substance one degree celcius

Question 28

Molar heat content

Answer 28

Is a value that can be located in a data booklet or it can be calculated, is always defined in terms of a chemical equation, either a phase change or a chemical reaction

Question 29

Calorimeter

Answer 29

Is a device used to measure the amount of energy emitted or absorbed during an energy change. Is an insulated container usually containing water, energy change carried out in the calorimeter causes the temperature of the water to change. Calculate the amount of energy involved in the experiment

Question 30

Laws of thermodynamics

Answer 30

Energy cannot be created or destroyed, only changed from one form to another (law of conservation of energy) Heat flows from hot objects to cooler ones until thermal equilibrium is reached

Question 31

When there is heat exchange...

Answer 31

Total heat lost = total heat gained

Question 32

Hess' law states that

Answer 32

When a reaction can be expressed as the algebraic sum of a sequence of two or more reactions, then heat of this reaction will be the algebraic sum of the heat of these reactions.

Question 33

Heat of reaction | Simplified hess' law

Answer 33

The sum of the head of formation of the products monies the sum of the heats of formation of the reactants

Question 34

Nuclear Reactions

Answer 34

Extremely large forces are needed to hold nuclear particles together, so extremely large quantities of energy are required to break these intranuclear bonds. Extremely large amounts of energy are released when particles reassemble (bond to form different atoms). Nuclear entertain changes only observed when nuclear reactions occur

Question 35

Fission Reactions

Answer 35

Involve splitting a nucleus

Question 36

Fusion reactions

Answer 36

Involve joining (fusing) two or more nuclei

Question 37

Relative heats of reaction

Answer 37

Lowest to highest 1. Warming/cooling 2. Phase change 3. Chemical change 4. Nuclear change