Chapter 2: 2.1 Heat, Work, and Energy

Question 1

Define:

Thermodynamics

Answer 1

The study of the energy changes involved in physical and chemical processes

Question 2

Define:

Thermochemistry

Answer 2

The branch of thermodynamics that investigates the heat flow that occurs during these reactions

Question 3

Explain the difference between a “food/large calorie” (Cal) and a “small calorie” (cal)

Answer 3

Food calories are typically seen on food packages, and are actually 1000 cal
Small calories are used in thermodynamics

Question 4

Define:

1 calorie

Answer 4

1 small calorie is equal to 4.184 Joules

Question 5

Define

1 Calorie

Answer 5

1 Cal = 4.184 kJ

Question 6

What is another well known definition of a large/food calorie?

Answer 6

Approximately the amount of energy needed to raise the temperature of 1 kg of water by 1 degrees Celsius (4.184 kJ)

Question 7

True or False:

Heat always flows from cool to warm

Answer 7

False, heat always flows from the warmer object to the cooler object

Question 8

State:

3 types of systems

Answer 8

1. Open system
2. Closed system
3. Isolated system

Question 9

Define:

Open system

Answer 9

Can exchange both matter and energy with its surroundings

Question 10

Define:

Closed system

Answer 10

Can exchange energy but not matter with its surroundings

Question 11

Define:

Isolated system

Answer 11

Exchanges neither matter nor energy with its surroundings

Question 12

Define:

Energy

Answer 12

“The capacity to do work”
Work is defined as the product of a force acting on an object and the distance that the object moves in response to the force

Question 13

What type of work are chemists usually interested in?

Answer 13

Pressure-Volume (PV) Work

Question 14

Define:

Pressure-Volume Work

Answer 14

Work involved in the expansion or compression of gases

Question 15

State and formula and units of:

PV work

Answer 15

w = -P * ΔV
Units in kPa L (1 kPa L = 1 J)

Question 16

List and describe:

Some types of energy

Answer 16

• Heat energy (thermal energy): The energy transferred due to a temperature difference bewteen the system and the surroundings
• Kinetic energy: The energy associated with motion
• Potential energy: Stored energy or the energy a body possesses due to its position

Question 17

True or False:

Chemical energy is a form of thermal energy

Answer 17

False, chemical energy is a form of potential energy

Question 18

True or False:

Energy can be created

Answer 18

False, energy cannot be created/destroyed; it can only be converted

Question 19

Define:

Heat capacity

Answer 19

The parameter used to estimate the heat energy associated with temperature changes

Question 20

What is a related quantity to heat capacity?

Answer 20

Specific heat capacity

Question 21

What is the amount of heat transferred denoted by? What is it related to?

Answer 21

• Denoted by q
• Related to temperature difference (ΔT) and heat capacity/specific heat capacity

Question 22

For heat capacity, state:

• What it is used for
• Notation
• Units

Answer 22

• Usually used for objects
• Represented by the symbol C
• Units: Joules/Degrees Celsius

Question 23

State the relation/formula for:

Heat capacity

(State the variables)

Answer 23

q = C * ΔT
* q: Amount of heat energy
* C: Object’s heat capacity
* ΔT: Temperature change

Question 24

For specific heat capacity, state:

• Definition
• Notation
• Units

Answer 24

• The heat needed to warm one mass unit (g or kg) of a substance by one degree
• Represented by lowercase c
• SI unit: Joules/Kilogram * Degrees Celsius
• Common unit: Joules/Gram * Degrees Celsius

Question 25

# State the relation/formula for: Specific heat capacity

Answer 25

q = m * c * ΔT

Question 26

# True or False: When calculating amount of heat transferred, all Celsius units can be swapped with Kelvin units

Answer 26

True, as we are using the temperature difference

Question 27

# Define: Temperature change

Answer 27

The difference between final and initial temperatures * ΔT = Tfinal - Tinitial

Question 28

# When calculating temperature difference: What do we have to ensure?

Answer 28

Tfinal and Tinitial are using the SAME SCALE

Question 29

When a system absorbs energy from the surroundings...

Answer 29

The process is endothermic and change in energy is positive

Question 30

When a system releases energy to the surroundings...

Answer 30

The process is exothermic and the change in energy is negative

Question 31

# State the relation between: ΔT and energy change (q)

Answer 31

* -ΔT = -q, system cools * +ΔT = +q, system warms

Question 32

# True or False: The sign of q is the same as sign of ΔT

Answer 32

True

Question 33

Does heat move from cool to warm or the other way?

Answer 33

Heat always goes from warm to cool

Question 34

# In heat transfer between objects: State the change of heat, ΔT, and q for the warmer object

Answer 34

* Loses heat and cools down * ΔT < 0 * q (lost) is negative

Question 35

# In heat transfer between objects: State the change of heat, ΔT, and q for the cooler object

Answer 35

* Gains heat and warms up * ΔT > 0 * q (gained) is positive

Question 36

What must the number of joules lost by the warmer object equal to?

Answer 36

The number of joules gained by the cooler object

Question 37

What is it called when both objects reach the same final temperature (Tf)? What is a formula that represents this?

Answer 37

Thermal Equilibrium * -q (lost) = q (gained)

Question 38

# Define and give examples of: Intensive (intrinsic) property

Answer 38

A property that has the same value regardless of the sample size * E.x. Temperature (melting and boiling points), Density

Question 39

# Define and give examples of: Extensive (extrinsic) property

Answer 39

A physical property whose value increases with the sample size * E.x. Mass, Volume, Energy, Enthalpy, and Entropy

Question 40

# Define and give examples of: State function

Answer 40

A property whose value depends ony on the current state of the system, not on how that state was reached * E.x. Volume, Pressure, Enthalpy * NOT Heat and Work

Question 41

# State: 1st Law of Thermodynamics

Answer 41

The total energy of an isolated system is conserved

Question 42

How do we keep track of the energy of a system?

Answer 42

A thermodynamic function called * Internal Energy (E)*

Question 43

# Define: Internal energy (E)

Answer 43

E is the sum of all the kinetic and potential energies of all the atoms, ions, and molecules in the system

Question 44

Can internal energy be measured?

Answer 44

No it cannot, but change in internal energy can be measured

Question 45

What are some ways to measure ΔE?

Answer 45

q - heat w - work

Question 46

For a system at constant pressure, how is work calculated?

Answer 46

w = -P * ΔV

Question 47

# In gas expansion, state: * How is work being done * Value of w * Change in work energy

Answer 47

* Gas (system) does work on surroundings * w is negative * Lost work energy

Question 48

# In gas compression, state: * How is work being done * Value of w * Change in work energy

Answer 48

* Surroudnings does work on gas (system) * w is positive * Gained work energy

Question 49

What happens if the process does not involve a compression or expansion? What would be the value of w?

Answer 49

* The change in volume would be zero * The value of w is zero

Question 50

What does ΔE equal?

Answer 50

ΔE = q + w

Question 51

# Determine what happens to the internal energy of the system when: Surroundings do work on, or supply heat to the system

Answer 51

* Internal energy of the system increases * ΔE > 0

Question 52

# Determine what happens to the internal energy of the system when: The system does work on, or supplies heat to the surroundings

Answer 52

* Internal energy of the system decreases * ΔE < 0

Question 53

When the system is kept at a constant volume, what happens to the relationship with ΔE?

Answer 53

* w = 0 * The relationship becomes E = q, commonly written as E = qv | The subscript v in qv signifies the constant volume

Question 54

# Theorem: What does the internal energy changes of a system equal when the volume doesn't change?

Answer 54

The internal energy change of a system is equal to the heat transferred when the volume does not change