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Chemistry 30 > Unit 2: Energy > Flashcards

Unit 2: Energy Flashcards

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1
Q

What is an Intra-molecular Force?

A

A force that acts within a molecule

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2
Q

Two types of intra-molecular bonds? + Characteristics

A 
Covalent Bonds (e- are shared): 
Strongest bond, lot's of energy needed to break,
Ionic Bonds (e- are transferred): 
Very strong, +/- attraction

Both are Potential/STORED energy (Ep)

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3
Q

What is an Inter-molecular Force?

A

A force that acts between molecules

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4
Q

What is the difference between Strong/Weak intermolecular forces?

A

Strong: High melting/boiling point. Liquids or solids

Weak: Low melting/boiling point. Gaseous

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5
Q

What are the three kinds of intermolecular forces?

A

1) London Dispersion
2) Dipole Dipole
3) Hydrogen Bonding

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6
Q

London Dispersion

A
  • Weakest bond of the three
  • Also known as an instantaneous dipole
  • All molecules have this
  • Non-polar molecules
  • More e-, more attraction (more valence shells = larger force)
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7
Q

Dipole-Dipole

A
  • Second strongest
  • Only occurs in polar molecules
  • Positive and negative ends of molecules attract
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8
Q

Hydrogen Bond

A
  • Occurs between Hydrogen and Fluorine, Oxygen, Nitrogen (due to high electronegativity)
  • Strongest
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9
Q

Potential Energy (Ep)

A
  • Chemical energy
  • Stored energy in the bonds within and between molecules
  • Ep changes in phase change without temperature change
  • Change in intramolecular bonds
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10
Q

Kinetic Energy (Ek)

A
  • Energy of motion of atoms, ions, and molecules
  • Translational, Rotational, Vibrational motion
  • Temperature dependent
  • Changes in intermolecular bonds
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11
Q

Thermochemistry

A

Study of energy/heat transfers of chemical and physical processes

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12
Q

Heat

A

Form of energy that flows between two samples at different temperatures

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13
Q

2nd law of thermodynamics?

A

-Heat is spontaneously transferred from hot to cold until it reaches thermal equilibrium

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14
Q

What is the source of all energy?

A

The sun

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15
Q

Temperature

A
  • average kinetic energy of the molecules
  • not the total energy
  • only energy of the RANDOM MOVEMENT
  • Higher temperature = faster particle movement
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16
Q

Thermal Energy

A

Measure of total kinetic heat energy

-Heat + Temp

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17
Q

How are heat and temperature interchangeable?

A

If something absorbs heat energy, the temperature will increase (excluding phase change)

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18
Q

What are Condensed phases?

A
  • When particles are close together
  • Solids and liquids
  • Held by INTERmolecular forces`
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19
Q

Solid phase

A
  • Strong intermolecular bonds
  • ONLY vibrational motion
  • Particles packed together, super dense
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20
Q

Liquid phase

A
  • Enough kinetic energy to break the SOME intermolecular bonds
  • Vibrational, rotational, and translational motion
  • Loosely bond
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21
Q

Gases phase

A
  • So much kinetic energy that intermolecular bonds become negligible
  • Little vibrational, rotational, but mostly translational motion
  • Particles are far apart
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22
Q

Heat capacity + Units

A
  • Measure of energy required to raise that amount of a substance by 1 degree
  • Can change depending on amount of substance
  • (J/Celcius)
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23
Q

Molar Heat Capacity, what can it tell us? + Units

A
  • How much heat energy is required to raise 1 mol of a substance 1 degrees
  • Allows comparance of the energy required for different substances to heat/cool
  • (J/mol x Celcius)
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24
Q

Specific Heat Capacity + Units

A
  • How much heat energy is required to raise 1 g of a substance 1 degrees
  • (J/g x Celcius)
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25
Q

What does a high Specific Heat Capacity mean?

A
  • Requires more energy to heat/cool
  • Releases more energy
  • Stores more energy
26
Q

Why is water a good coolant?

A
  • High specific heat capacity
  • More energy to heat up
  • Stores heat well
27
Q

What characteristics allow a substance to store more energy?

A
  • High Specific Heat capacity

- Greater mass

28
Q

Formula that can be used to find Energy required to heat/cool substances? Units?

A

Ek=mc(delta)t

Ek= Kinetic energy (J)
m= mass of substance (g)
c= Specific heat capacity (J/g x Celsius)
delta t = change (final - initial_ in temperature (Celsius)

Must be same substance

29
Q

Exothermic

A
  • Loses Heat

- Negative Kinetic energy

30
Q

Endothermic

A
  • Gaining Heat

- Positive Kinetic energy

31
Q

What is 1ml of H2O equal to?

A

1g of H2O

32
Q

Enthalpy

A
  • Also known as heat
  • Total energy possessed in a system
  • How much energy can be exchanged with surroundings
  • Can be different if substance is at a different state or substance is at a different temperature
  • Can only find change in Enthalpy
33
Q

Molar Enthalpy + Units

A
  • The heat/energy that is possessed when 1 mol of a substance is formed from its simple compounds
  • KJ/mol
  • Negative = Exothermic
  • Positive = Endothermic
  • Can find in equation if (Heat energy/Mol)
34
Q

◮rH°

A

Molar enthalpy of reaction

35
Q

◮cH°

A

Molar enthalpy of combustion

36
Q

◮fH°

A

Molar enthalpy of formation (in data book)

37
Q

◮dH°

A

Molar enthalpy of decomposition (opposite sign of formation)

38
Q

Endothermic

A
  • Energy is absorbed
  • Energy is gained by system, lost by surrounding
  • Energy of Products > Reactants
  • Energy is a reactant
  • POSITIVE
39
Q

Exothermic

A
  • Energy is released/given off
  • Energy is lost by system, gained by surrounding
  • Energy of Products < Reactants
  • Energy is product
  • NEGATIVE
40
Q

Ep=n◮rH° + units

A 
Ep= Potential Energy (KJ)
n= moles (mol)
◮rH°= Molar enthalpy of reaction (KJ/mol)
°= standard conditions
41
Q

4 ways of communicating Enthalpy Change?

A

1) Molar Enthlapy
2) Enthalpy change
3) Thermochemical Reactions
4) Energy Potential Diagrams

42
Q

When products have more energy than reactants, What kind of reaction?

A

Endothermic (+)

43
Q

When products have less energy than reactants, what kind of reaction?

A

Exothermic (-)

44
Q

Enthalpy Change

A

-Shows as ◮H in equation
- = released
+ = Absorbed
-Changes depending on number of mols in equation

45
Q

Thermochemical Equations

A
  • Energy is reactant if it is absorbed
  • Energy is product if it is released
  • KJ
  • Can use standard enthalpes as long as equation is based on 1 mol
  • Remember state and elements have 0 energy
46
Q

Potential energy diagrams

A
  • Endothermic: reactants have less energy and absorbed so products have more energy
  • Exothermic: reactants have more energy and energy is released so products have less
  • Most exothermic reactions require activation energy
  • Formation is mostly exothermic
47
Q

Two musts for Collision Theory

A
  • Right orientation

- Must pass minimal energy required

48
Q

What is activation energy?

A

-Minimal energy required

49
Q

What does a catalyst do? 5 points

A
  • Speed up reaction
  • decrease activation energy
  • New pathway
  • NO reaction
  • no change in delta H
50
Q

CFC

A

Catalyst: o3 to O2

51
Q

Sulfuric Acid

A

Catalyst: Oil industry

52
Q

Nitric Acid

A

Catalyst for fertelizer

53
Q

Enzymes

A

catalyst for biological processes

54
Q

Catalytic Convertor

A

Used in cars: Nox +Co to No2 and Co2

55
Q

Two assumptions in calorimetry?

A

1) Energy is conserved, not loss to environment

2) Heat flows from hot to cold until thermal equilibrium is reached

56
Q

Proportion of Heat loss/gain?

A

Heat loss will be opposite but equal to heat gain

57
Q

Styrofoam calorimeter? Equation

A

-Styrofoam is a good insulator, no gain of heat

n◮rH°=mc◮t

58
Q

Metal can Calorimeter? equation

A
  • conductors used for combustion
  • Metal also absorb heat
  • Temp change the same due to conductors
  • n◮rH°=mc◮t(water)+mc◮t(metal)
59
Q

Bomb Calorimeter? Advantages?

A

-02 gas surrounded by h20 (l)
- used for Explosive rxns = heat to water
n◮rH°=C◮t (C is the HEAT capacity of bomb =energy to raise entire calorimeter 1 degree)
-No mass
-Accounts for differences in heat loss/gain

60
Q

When is H2O g?

A

In a bomb calorimeter when the system is open

61
Q

Does delta H change when looking at Ea(reverse)?

A

No, but the sign will change

Chemistry 30 (1 decks)

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