Thermochemistry - Nature of Energy

Question 1

What is thermochemistry?

Answer 1

The study of energy changes during physical or chemical changes in matter

Question 2

What do all thermodynamics depend on?

Answer 2

The law of conservation of energy

Question 3

The law of conservation of energy states…

Answer 3

Energy cannot be created nor destroyed

Question 4

Potential Energy (PE)

Answer 4

• Energy due to the position or composition of an object
• Stored Energy

Question 5

Kinetic Energy (KE)

Answer 5

• Energy of motion
• Depends on mass of object and its velocity

Question 6

Calculation of thermal energy

Answer 6

Thermal Energy=PE + KE

Question 7

Changes that occur in matter may be classified into….

Answer 7

Physical, chemical or nuclear changes

Question 8

Physical Change

Answer 8

• Change in form or state of a substance
• No chemical bonds are broken
• Least energy

Question 9

Chemical Change

Answer 9

• Change in chemical bonds between atoms resulting in new substances

Question 10

Nuclear Change

Answer 10

• Change in the protons or neutrons in an atom resulting in a new atom
• Most energy

Question 11

What is a System?

Answer 11

The substance undergoing a change

Question 12

What are the surroundings?

Answer 12

• Describes the system’s environment
• Includes all matter that is not part of the system

Question 13

What is thermal energy?

Answer 13

• Total amount of movement (kinetic energy) of the particles in a system and the stored energy within these particles (potential energy)

Question 14

What does thermal energy depend on?

Answer 14

• How many particles are moving and their temperature

Question 15

What is temperature?

Answer 15

• Measures the average speed of particles in a sample
• Measured in ℃ or K

Question 16

What is heat?

Answer 16

• The amount of thermal energy transferred between substances
• Due to a temperature difference
• Measured in Joules (J)

Question 17

Extensive Property

Answer 17

• Directly depends upon the amount of substance

Question 18

Example of an extensive property

Answer 18

Heat

Question 19

Intensive Property

Answer 19

• Not related to the amount of the substance

Question 20

Example of an intensive property

Answer 20

Temperature

Question 21

State Function

Answer 21

Property that depends only on its current state and not on how that state was reached

Question 22

Exothermic - Thermal energy (q)

Answer 22

Released

Question 23

Exothermic - Direction of the flow of heat

Answer 23

System —> Surroundings

Question 24

Exothermic - Temperature Change

Answer 24

• Tf>Ti
• ΔT>0
• Postive

Question 25

Exothermic - Sign of ΔH

Answer 25

- ΔH<0 - Negative

Question 26

Exothermic - Energy Term

Answer 26

- Product - A + B ---> C + energy

Question 27

Endothermic - Thermal Energy (q)

Answer 27

Absorbed

Question 28

Endothermic - Direction of the flow of heat

Answer 28

Surroundings ---> System

Question 29

Endothermic - Temperature Change

Answer 29

- Tf

Question 30

Endothermic - Sign of ΔH

Answer 30

- ΔH>0 - Postive

Question 31

Endothermic - Energy Term

Answer 31

- Reactant - A + Energy ---> B + C

Question 32

Open System

Answer 32

- Both matter and energy can move between the system and the surroundings

Question 33

Open System Example

Answer 33

Boiling pot of water

Question 34

Closed System

Answer 34

Can exchange energy but not matter with its surroundings

Question 35

Closed System Example

Answer 35

Covered pot of water

Question 36

Isolated System

Answer 36

- Neither energy nor matter can move into or out of the system - Will still be some energy loss

Question 37

Isolated System Example

Answer 37

Insulated thermos