Chapter 2.1: Heat, Work, & Energy

Question 1

What is thermodynamics?

Answer 1

study of the energy changes involved in physical and chemical processes

Question 2

What are some examples of physical processes?

Answer 2

heating and cooling a substance, phases changes, changes in physical parameters (volume, pressure of a gas)

Question 3

What is thermochemistry?

Answer 3

thermodynamics relating to heat flow, or change In heat energy, occurring in chemical reactions

Question 4

How does the food “calorie” compare to the energy unit “calorie”?

Answer 4

food calorie (Cal) is equal to 1000 calories

Question 5

How does 1 calorie compare in joules?

Answer 5

1 cal = 4.184 J; (energy to raise the temperature of 1g of water by 1ºC)

1 Cal = 4.184 kJ (amount of energy needed to raise the temperature of 1 kg of water by 1ºC)

Question 6

What is heat flow?

Answer 6

transfer of thermal energy in a process

Question 7

In what direction does heat flow?

Answer 7

from warmer object to the cooler object until thermal equilibrium is reached

Question 8

What is an open system?

Answer 8

system exchanges matter and heat with surroundings

Question 9

What is a closed system?

Answer 9

system exchanges heat with surroundings

Question 10

What is an isolated system?

Answer 10

system exchages nothing with surroundings (no heat or matter)

Question 11

What is energy?

Answer 11

the capacity to do work

Question 12

What is work?

Answer 12

product of force and distance

Question 13

What is calorimetry?

Answer 13

experimental way to measure enthalpy change

Question 14

What is q(cal)?

Answer 14

heat in calorimeter assembly (container, lid, thermometer)

Question 15

what is q(rxn)?

Answer 15

reactants/reaction

Question 16

what is q(sol)?

Answer 16

solvent/solution

Question 17

How is temperature change measured in a reaction?

Answer 17

temperature change of calorimeter and solution
- increase in heat of surrounding = decrease heat in reaction
- decrease in heat of surrounding = increase heat in reaction

Question 18

What is simple calorimetry?

Answer 18

experiment occurs under constant pressure
- q(rxn) = ∆H(rxn) when H is enthalpy

Question 19

What is thermal/heat energy?

Answer 19

energy transferred due to a temperautre difference between the system

Question 20

What is kinetic energy?

Answer 20

energy associated with motion

Question 21

What is potential energy?

Answer 21

stored energy possessed by a body due to position

Question 22

What is chemical energy?

Answer 22

• type of potential energy

Question 23

how is work related with pressure and volume?

Answer 23

w = -P * ∆V (in kPa L)
- work involved in the expansion or compression of gases

Question 24

What an endothermic reaction?

Answer 24

heat gained/absorbed by system:
q(rxn) > 0
q(sol) < 0

Question 25

What is an exothermic reaction?

Answer 25

heat lost/released by system:
q(rxn) < 0
q(sol) > 0

Question 26

What is heat capacity (C) ?

Answer 26

heat needed to heat apparatus 1 degree ºC or ºK used for objects and each piece of apparatus
- used in q(Cal) = C ∆T

Question 27

What is specific heat capacity (c)?

Answer 27

similar to heat capacity but consideres the mass of the substance
- heat needed to warm one mass unit (g or kg) of a substance by 1 degree
- in J/g K
- used in q(sol) = m c ∆T

Question 28

What is the relationship between heat capacity and energy to increase temperature?

Answer 28

higher heat capacity = more energy needed to increase temperature

Question 29

What is ∆T?

Answer 29

temperature change: T(final) - T(initial)

either both in Kelvin or Celcius

Question 30

How is thermal equilibrium represented?

Answer 30

-q(lost) = q(gained)
- both objects reach the same temperature

Question 31

What is an intensive/intrinsic property?

Answer 31

property that has the same value regardless of sample size (doesn’t depend on the amount of material)

Question 32

What are intensive/intrinstic property examples?

Answer 32

temperature, MP, BP, density

Question 33

What is an extensive/extrinsic property?

Answer 33

physical property what increases with sample size (depends on amount of material)

Question 34

What are extensive/extrinsic property examples?

Answer 34

mass, volume, energy, enthapy, and entropy

Question 35

What is a state function?

Answer 35

property whose value depends only on the current state of the system, but not how that state was reached (doesn’t depend on route taken, only depends on initial and final state)

Question 36

What are examples of state functions?

Answer 36

volume, pressure, enthalpy

Question 37

What is the first law of thermodynamics?

Answer 37

total energy of an isolated system is conserved
- no energy lost to surroundings and heat exchange only occurs within the system
- energy can be transferred from one part of the system to another, or converted from on form to another, but it cannot be created or destroyed

net change in heat = q(sys) = 0 = q(rxn) + q(cal) + q(sol)

Question 38

What is internal energy (E)?

Answer 38

sum of all kinetic and potential energies of all atoms, ions, and molecules in a system
- extensive property and state function

Question 39

What is meant by expansion of a gas?

Answer 39

the gas (system) is doing work on surroundings and value of w is negative
- work energy has been used so it has been removed from the system

Question 40

what is mean by compression of a gas?

Answer 40

the surroundings are said to be doing work on the system, and the value of w is positive
- the system has gained work

Question 41

When is w = 0?

Answer 41

when a process does not involved compression or expansion and there is not volume change (∆V = 0)