6.1.2 Chemical Energy and Enthalpy

Question 1

Can a molecule reach absolute zero?

Answer 1

No.

All molecules contain thermal energy.

Question 2

Define Thermal Energy

Answer 2

Thermal energy is the randomized kinetic energy associated with the various motions the molecules as a whole, including the atoms within, undergo.

Question 3

Define Kinetic Energy

Answer 3

The energy that deals with anything in motions including but no limited to atoms and molecules.

Question 4

Define Potential Energy

Answer 4

Potential energy is energy that is stored within an object, not in motion but capable of becoming active.

Potential energy has the potential of turning into kinetic energy, the energy of motion.

Question 5

Anything in motion displays ______.

Answer 5

Kinetic energy.

Question 6

Potential energy has the ______ of turning into ______ energy.

Answer 6

The potential of turning into kinetic energy, the energy of motion.

Question 7

What is kinetic energy?

Answer 7

It is the energy of motion.

Question 8

How can molecules convert energy from one form into another?

Answer 8

With the uptake and release of heat, molecules form, break and rearrange their chemical bonds.

Question 9

What is heat?

Answer 9

Heat is the transfer of kinetic energy from one medium or object to another, or from an energy source to a medium or object.

Question 10

When a kettle is placed on an oven burner, what is happening?

Answer 10

Heat is happening, kinetic energy is being transferred from the burner into the kettle.

Question 11

In the case of a kettle and oven burner, which is the energy source and medium?

Answer 11

The kettle is the medium while the oven burner is the energy source.

Question 12

Define Translation

Answer 12

Translation refers to the movement of an object as a complete unit.

Question 13

In gaseous hydrogen, what is it called when the molecules move freely from one location to another?

Answer 13

Translational Motion.

Question 14

Define Natural Vibrational Frequency

Answer 14

Natural vibrational frequency (NVF) is the frequency which, in this case, atoms vibrate at.

The frequency which the chemical bonds spring between the H2 atoms.

Question 15

List the three kinetic energy motions.

Answer 15

Translational Kinetic Energy (KEtrans)
Vibrational Kinetic Energy (KEvib)
Rotational Kinetic Energy (KErot)

Question 16

Define Heat Capacity

Answer 16

Heat capacity is the number of heat units needed to raise the temperature of a body by one degree.

Question 17

What is temperature?

Answer 17

Temperature is a measure of the average kinetic energy due to translational motions of molecules.

Question 18

Define Temperature

Answer 18

Due to the translation motion of the molecule, temperature is the average kinetic energy measurement.

Question 19

Describe internal energy (U).

Answer 19

Internal energy (U) is the total energy of the molecule.

Question 20

What are the three ways heat transfer occurs?

Answer 20

Radiation
Conduction
Convection

Question 21

What is thermal energy?

Answer 21

Thermal energy is randomized translational

kinetic energy.

Question 22

What is heat capacity?

Answer 22

Heat capacity is how easy (or difficult) it is to increase the temperature of a body or object.

Question 23

Define Monatomic Molecules

Answer 23

Molecules with one atom.

Question 24

Define Diatomic Molecules

Answer 24

Molecules with two atoms.

Question 25

Define Triatomic Molecules

Answer 25

Molecules with three atoms.

Question 26

Define Polyatomic Molecules

Answer 26

Molecules with two or more atoms.

Question 27

Which have a lower heat capacity monatomic or polyatomic molecules?

Answer 27

Monatomic molecules, since all energy ends up in translational motions it all goes into increasing the temperature.

Question 28

Why do polyatomic molecules have a higher heat capacity?

Answer 28

In a polyatomic gas, the absorbed energy is partitioned among the other kinds of motions (vibrational and rotational motion); since only the translational motions contribute to the temperature, the temperature rise is smaller, and thus the heat capacity is larger.

Question 29

What motion contributes to temperature rise?

Answer 29

Translation motion.

Question 30

What does a "degree of freedom" mean?

Answer 30

Think of a "degree of freedom" as a kind of motion that adds kinetic energy to a molecule.

Question 31

In the case of motions modes, what does quantized mean?

Answer 31

This means that only certain increments of energy are possible for each mode of motion, and unless a certain minimum amount of energy is available, a given mode will not be active at all and will contribute nothing to the heat capacity.

Question 32

What is the Dulong and Petit Law?

Answer 32

In metals, the atoms oscillate about their equilibrium positions in a rather uniform way which is essentially the same for all metals, so they should all have the same heat capacity.

Question 33

Define an exothermic reaction.

Answer 33

A reaction which releases heat. The opposite of an exothermic reaction is an endothermic reaction.

Question 34

Define an endothermic reaction.

Answer 34

A reaction which absorbs heat. The opposite of an endothermic reaction is an exothermic reaction.

Question 35

What property is energy?

Answer 35

Extensive property.