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CHEM141Z CH 7 - Thermochemistry > Powerpoint Definitions > Flashcards

Powerpoint Definitions Flashcards

1
Q

thermodynamics

A

is the study of energy and its transformations.

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2
Q

thermochemistry

A

is a branch of thermodynamics that deals with the energy involved with chemical and physical changes.

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3
Q

fundamental premise of thermochemistry

A

When energy is transferred from one object to another, it appears as work and/or as heat

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4
Q

First Law of Thermodynamics

A

The total energy of the universe is constant

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5
Q

What is energy in terms of work?

A

Energy is the capacity to do work

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6
Q

What is work? What are the units?

A

Work is force applied over a distance. Work = Force x Distance = mass x acceleration x distance w = kg x m/s2 x m = N x m = kg x m2 / s2 = joule (J)

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7
Q

What are the units of work?

A

w = kg x m/s2 x m = N x m = kg x m2 / s2 = joule (J

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8
Q

What standard SI unit does Joule correspond to?

A

The joule is the SI unit of energy.

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9
Q

What is work and heat in terms of energy?

A

Work is energy Heat is also energy

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10
Q

What NON standard SI unit does calorie correspond to?

A

The calorie is the non-SI unit of energy.

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11
Q

What is the nonSI and SI unit of energy?

A

The calorie is the non-SI unit of energy. The joule is the SI unit of energy.

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12
Q

What is a calorie?

A

A calorie is the amount of (heat) energy required to raise 1 g of water 1 °C. 1 cal = 4.184 J

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13
Q

What is a large calorie and what is it abbreviated as?

A

The “large” calorie is equal to one kcal and sometimes abbreviated Cal.

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14
Q

What are calories on a nutritional label and where do they come from?

A

Calories on nutritional labels are Calories, or kcal, thanks to Professor Wilbur Olin Atwater…

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15
Q

What do you do with energy?

A

Energy can be used or stored

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16
Q

Kinetic energy

A

Kinetic energy is energy in motion. It is how we describe the energy of moving objects.

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17
Q

Thermal energy

A

Thermal energy is heat energy, but since heat is created by molecular motion, it is a type of kinetic energy.

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18
Q

What is thermal energy in terms of kinetic energy?

A

Kinetic energy is energy in motion. It is how we describe the energy of moving objects. Thermal energy is heat energy, but since heat is created by molecular motion, it is a type of kinetic energy.

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19
Q

Potential energy

A

Potential energy is stored energy. It can be converted to kinetic energy to do work.

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20
Q

Chemical energy

A

Chemical energy is the energy stored in chemical bonds. It is a type of potential energy

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21
Q

What is chemical energy in terms of kinetic energy?

A

Potential energy is stored energy. It can be converted to kinetic energy to do work. Chemical energy is the energy stored in chemical bonds. It is a type of potential energy

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22
Q

What does the first law of thermodynamics say about the energy of the universe, system, surroundings?

A
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23
Q

what is the internal energy of the system?

A

is called the internal energy of the system, and it is an example of a state function

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24
Q

What is the value of a state function?

A

The value of a state function is only dependent on the values of the final and intial state of a system, regardless of how it changed.

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25
Q

What is delta?

A

The Greek letter delta (triangle) denotes a change, and it is always defined as the final state – the initial state

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26
Q

What are the 2 pathways of energy in a system?

A
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27
Q

What is energy transfer in terms of work and heat?

A

When energy is transferred from one object to another, it appears as work and/or as heat

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28
Q

What is the internal energy of the system and surroundings in terms of work and heat?

A
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29
Q

What is the energy diagram like for transfer of internal energy between a system and its surroundings? How do you find deltaE from final/initial and products/reactants?

A
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30
Q

When a system transferring energy as heat (q) only, what happens to q in the 2 situations?

A

deltaE must be + or -

but q is a quantity to be careful with signs

When heat is lost to the surroundings, q <0

when heat is gained from surroundings q > 0

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31
Q

what is thermal equilibrium?

A

Thermal equilibrium is when heat transfer stops because the system is at the same temperature as the surroundings.

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32
Q

What is heat capacity?

A

Heat capacity (C) is the heat energy required to raise the temperature of a body by 1 K.

  • Units are joules/kelvin (J/K)
  • Also remember DT (ºC) = DT (K)
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33
Q

Is heat capacity intensive or extensive property?

A

Heat capacity is an extensive property – the more mass there is, the higher the heat capacity

34
Q

What is specific heat capacity?

A

Specific heat capacity (Cs) is the heat energy required to raise the temperature of one gram of a substance by 1 K. Specific heat capacity is an intensive property.

• Units are J/g·K

35
Q

What are the unit of heat capacity and specific heat capacity?

A

Heat capacity (C) in joules/kelvin (J/K)

Specific heat capacity (Cs) in J/gK

36
Q

How do you calculate heat capacity?

A

C = m x Cs

mass

Cs - specific heat capacity

37
Q

How do you quantify heat transfer?

A

q = C x deltaT = m x Cs x deltaT

C - heat capacity

deltaT = delta Temperature

m = mass

Cs = specific heat capacity

38
Q

What is molar heat capacity (Cm)

A

Molar heat capacity (Cm) is the heat energy required to raise the temperature of one mole of a substance by 1 K

units are J/mol x K

39
Q

What is the conversion from cal to Joules?

What is the conversion from 1 Cal to 1 kcal?

A

1 cal = 4.184 Joules

1 cal = 1kcal = 1000 cal

40
Q

Pressure-volume work, or PV work?

A

Pressure-volume work, or PV is the work created by the expansion of a gas against an external pressure, causing a change in volume?

41
Q
A
42
Q

How does PV work relate to the equation for w?

A

w = force x distance

w = P x A x deltaH

w = P x deltaV

43
Q

When work is leaving the system, what happens to the sign of PV work?

A

w = -(P x deltaV)

44
Q

at pressure applied what happens to the volume in final versus initial? What equation should be used?

A
45
Q
A
46
Q

What does it mean for q when its POS and NEG?

What it does mean for w when its POS and NEG?

A

For q:

+ means system gains heat

– means system loses heat.

For w:

+ means work done on system;

– means work done by system.

47
Q

What are the sign conventions for q, w, deltaEsystem?

A

POS q + POS w ==> POS internal energy of system

NEG q + NEG w ==> NEG internal energy of the system

POS q + NEG w ==> depends on the sizes (math)

NEG q + POS w ==> depends on the sizes (math)

48
Q

What is bomb calorimetry?

A

A kind of calorimetry that is constant volume

deltaV = 0

-Pext x deltaV = 0

w = 0

deltaEreaction = q of v

49
Q

What is Enthalpy (H)?

A

Enthalpy (H) is a thermodynamic quantity that is the total heat content of a system:

H = E + PV

ENTHALPY is just HEAT (q) at constant pressure, which we live in every day…

50
Q

Enthalpy is what in terms of heat and pressure?

A

ENTHALPY is just HEAT (q) at constant pressure, which we live in every day…

51
Q
A
52
Q

When deltaH is negative is it endothermic/exothermic?

When deltaH is positive is it endothermic/exothermic?

A

deltaH is negative ==> exothermic

deltaH is positive ==> endothermic

53
Q

What does heat of formation look like?

A
54
Q

What does heat of combustion look like?

A
55
Q

What does heat of solution look like?

A
56
Q

What does heat of vaporization look like?

A
57
Q

What is enthalpy of reaction?

A

Enthalpy of Reaction is the enthalpy change for a chemical reaction when molar amounts of each reactant are reacted completely to form products.

In other words, if one mole of C3H8 reacted with five moles of oxygen, 2044 kJ of heat would be released.

This makes DeltaHrxn a conversion factor for reaction heat…

58
Q
A
59
Q

What is the standard enthalpy of reaction?

A

Standard enthalpy of reaction: DH˚rxn value of DHrxn when all reactants and products are in their standard state

60
Q

Standard enthalpy of formation: deltaHf

What is it for elements and compounds?

A
  1. Elements: set as reference to 0 kJ/mol when an element is in its standard state
  2. Compounds: value of DH when exactly one mole is formed from its constituent elements in their standard states
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CHEM141Z CH 7 - Thermochemistry (4 decks)

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