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Chemistry 30 > Unit 2: Energy > Flashcards

Unit 2: Energy Flashcards

(61 cards)

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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
What does a high Specific Heat Capacity mean?
- Requires more energy to heat/cool - Releases more energy - Stores more energy
26
Why is water a good coolant?
- High specific heat capacity - More energy to heat up - Stores heat well
27
What characteristics allow a substance to store more energy?
- High Specific Heat capacity | - Greater mass
28
Formula that can be used to find Energy required to heat/cool substances? Units?
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
Exothermic
- Loses Heat | - Negative Kinetic energy
30
Endothermic
- Gaining Heat | - Positive Kinetic energy
31
What is 1ml of H2O equal to?
1g of H2O
32
Enthalpy
- 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
Molar Enthalpy + Units
- 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
◮rH°
Molar enthalpy of reaction
35
◮cH°
Molar enthalpy of combustion
36
◮fH°
Molar enthalpy of formation (in data book)
37
◮dH°
Molar enthalpy of decomposition (opposite sign of formation)
38
Endothermic
- Energy is absorbed - Energy is gained by system, lost by surrounding - Energy of Products > Reactants - Energy is a reactant - POSITIVE
39
Exothermic
- Energy is released/given off - Energy is lost by system, gained by surrounding - Energy of Products < Reactants - Energy is product - NEGATIVE
40
Ep=n◮rH° + units
``` Ep= Potential Energy (KJ) n= moles (mol) ◮rH°= Molar enthalpy of reaction (KJ/mol) °= standard conditions ```
41
4 ways of communicating Enthalpy Change?
1) Molar Enthlapy 2) Enthalpy change 3) Thermochemical Reactions 4) Energy Potential Diagrams
42
When products have more energy than reactants, What kind of reaction?
Endothermic (+)
43
When products have less energy than reactants, what kind of reaction?
Exothermic (-)
44
Enthalpy Change
-Shows as ◮H in equation - = released + = Absorbed -Changes depending on number of mols in equation
45
Thermochemical Equations
- 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
Potential energy diagrams
- 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
Two musts for Collision Theory
- Right orientation | - Must pass minimal energy required
48
What is activation energy?
-Minimal energy required
49
What does a catalyst do? 5 points
- Speed up reaction - decrease activation energy - New pathway - NO reaction - no change in delta H
50
CFC
Catalyst: o3 to O2
51
Sulfuric Acid
Catalyst: Oil industry
52
Nitric Acid
Catalyst for fertelizer
53
Enzymes
catalyst for biological processes
54
Catalytic Convertor
Used in cars: Nox +Co to No2 and Co2
55
Two assumptions in calorimetry?
1) Energy is conserved, not loss to environment | 2) Heat flows from hot to cold until thermal equilibrium is reached
56
Proportion of Heat loss/gain?
Heat loss will be opposite but equal to heat gain
57
Styrofoam calorimeter? Equation
-Styrofoam is a good insulator, no gain of heat | n◮rH°=mc◮t
58
Metal can Calorimeter? equation
- conductors used for combustion - Metal also absorb heat - Temp change the same due to conductors - n◮rH°=mc◮t(water)+mc◮t(metal)
59
Bomb Calorimeter? Advantages?
-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
When is H2O g?
In a bomb calorimeter when the system is open
61
Does delta H change when looking at Ea(reverse)?
No, but the sign will change

Chemistry 30 (1 decks)

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