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Chemistry > Ch. 15- Energy > Flashcards

Ch. 15- Energy Flashcards

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1
Q

photosynthesis

A

the chemical process used by green plants to convert solar energy into chemical energy by reducing carbon dioxide and producing glucose and oxygen

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2
Q

our biosphere receives about 1 billionth of the sun’s energy output… where does that fraction of energy go?

A
  • 30% is immediately reflected back into space as UV & visible light
  • ~50% is converted to heat for a habitable planet
  • ~23% powers the water cycle
  • <0.02% is absorbed by green plants
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3
Q

what needs to be present for photosynthesis to occur?

A

chlorophyll & enzymes

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4
Q

what are the various energy units and when do we use them?

A
  • Calories or kcals (energy content of food)
  • joules (amount of energy in SI units)
  • watts (amount of power/the rate at which energy is used in SI units
  • kilowatt hour (the amount of energy consumed by a 1 kW device in 1 h)
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5
Q

how many cal are in 1 kcal?

A

1000 cal

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6
Q

how many kJ are in 1000 J?

A

1 kJ

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7
Q

how many J are in 1 cal?

A

4.18 J

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8
Q

how many W are in 1 J/s?

A

1 W

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9
Q

how many W are in 1 kW?

A

1000 W

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10
Q

how many kJ are in 1 kWh?

A

3600 kJ

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11
Q

how many s are in 1 h?

A

3600 s

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12
Q

potential energy

A

energy due to position or composition

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13
Q

kinetic energy

A

the energy of motion

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14
Q

kinetic energy

A

the energy of motion

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15
Q

system

A

the part of the universe under consideration in a thermochemical study

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16
Q

surroundings

A

everything that is not part of the system being observed in a thermochemical study

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17
Q

exothermic

A

describes a process that releases heat to the surroundings

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18
Q

enthalpy of reaction (heat of reaction)

A

the amount of energy released or absorbed in a reaction with stoichiometric amounts of each reactant

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19
Q

endothermic

A

describes a process that requires heat to occur, taking that energy from the surroundings

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20
Q

equation for determining if a chemical process is endothermic or exothermic

A

enthalpy change = (the sum of energy needed to break all the bonds) - (the sum of energy released in forming bonds)

  • *if enthalpy change is a negative number, its exothermic
  • *if enthalpy change is a positive number, its endothermic
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21
Q

equation for determining if a chemical process is endothermic or exothermic

A

enthalpy change = (the sum of energy needed to break all the bonds) - (the sum of energy released in forming bonds)

  • *if enthalpy change is a negative number, its exothermic
  • *if enthalpy change is a positive number, its endothermic
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22
Q

chemical kinetics

A

the study of reaction rates and factors that affect those rates (temperature, solute concentration, presence of a catalyst, etc.)

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23
Q

chemical kinetics

A

the study of reaction rates and factors that affect those rates (temperature, solute concentration, presence of a catalyst, etc.)

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24
Q

how does temperature affect the rate of a chemical reaction?

A

the higher the temperature, the faster the reaction occurs because the molecules move faster & collide more frequently, increasing chances of reaction

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25
Q

how does temperature affect the rate of a chemical reaction?

A

the higher the concentration, the faster the reaction occurs the because when we crowd molecules into a given volume of space, the molecules collide more often, increasing chances of reaction

26
Q

how do catalysts affect the rate of a chemical reaction?

A

certain catalysts can be used to speed up the chemical reaction by lowering the reaction’s activation energy (amount of energy needed to initiate the reaction)

27
Q

first law of thermodynamics (law of conservation of energy)

A

states that energy cannot be created or destroyed, only transformed from one form to another

28
Q

facts about energy that do not support the 1st law of thermodynamics

A
  • energy can be changed from one form to another
  • not all forms of energy are equally useful
  • more useful forms of energy are constantly being degraded into less useful forms or distributed in a way that make the energy nearly impossible to recover
29
Q

second law of thermodynamics

A

the forms of energy available for useful work are continually decreasing; energy spontaneously tends to distribute itself among the objects in the universe

30
Q

explain entropy with solids/liquids/gases

A
  • solids have low entropy
  • liquids have moderate entropy
  • gases have high entropy
31
Q

define microstates & explain their importance when determining entropy (this is mentioned in 15.4 in case you need to further look into it, considering you barely took notes on it)

A
  • 1 microstate is 1 possible arrangement of molecules in a substance; almost as if you were to take a screenshot of that substance, how many possible different screenshots you could take = however many possible microstates exist (considering molecules are in constant movement)
  • entropy is determined by the amount of microstates to possibly exist in a substance
32
Q

fuel

A

a substance that burns readily with the release of significant energy, ideally in a controllable manner

33
Q

fossil fuels

A

natural fuels, especially coal, petroleum, and natural gas, derived from once-living plants and animals

34
Q

fuels vs. non-fuels

A

(a) fuels are reduced forms of matter than release relatively large quantities of heat when burned
(b) non-fuels are compounds that are oxidized forms of matter

35
Q

which fossil fuels are likely to be depleted within the current century?

A

natural gas & petroleum

36
Q

name the fossil fuels

A

coal
petroleum
natural gas

37
Q

coal

A

a solid fossil fuel that is rich in carbon

38
Q

how were today’s coal deposits formed?

A
  • millions of years ago, Earth was warmer & plants flourished
  • overtime, some plant material became buried under mud & water
  • due to lack of oxygen, those plants decayed only partially, preserving much of the cellulose molecules they’re made up of
  • as they became buried deeper & deeper, pressure was increased & their cellulose molecules broke down
  • small molecules rich in hydrogen & oxygen escaped (mostly as water), leaving behind material increasingly rich in carbon
39
Q

pros of using coal as fuel

A
  • most plentiful fossil fuel

- can be used industrially & medically depending on how it’s burned

40
Q

cons of using coal as fuel

A
  • dangerous to obtain (coal mining = accidents & black lung disease)
  • ash leftover from combustion = PM; major air pollutant (airborne mercury)
  • combustion produces sulfur dioxide, coal’s primary pollutant
  • coal mining destroys surrounding land
41
Q

hydraulic fracturing (fracking)

A

a process for obtaining oil or natural gas whereby deep holes are drilled into geological formations, and high-pressured fluids (usually water mixed with fine sand) are pumped in to form cracks in the rocks through which the desired fluid may flow

42
Q

natural gas

A

a mixture of gases, mainly methane, found in underground deposits

43
Q

composition of typical natural gas

A
  • mainly methane
  • ethane
  • nitrogen
  • some propane
  • some carbon dioxide
  • tiny amounts of pentanes & butanes
44
Q

how do we use natural gas?

A
  • mainly as fuel (supplies ~23% of worldwide energy consumption)
  • as raw material to create other necessary products
45
Q

petroleum

A

a thick liquid mixture of (mostly) hydrocarbons with various impurities including sulfur, occurring in various geologic deposits

46
Q

products of combusted natural gas

A
  • mainly carbon dioxide & water

- when burned in insufficient air… carbon monoxide & soot

47
Q

products of combusted petroleum

A
  • carbon dioxide

- water vapor

48
Q

fractions of typical petroleum

A 
(in order from lowest to highest boiling points)
- petroleum gas
- gasoline
- kerosene
- heating oil
- lubricating oils/greases
- residues
(see chart in 15.7 for more details)
49
Q

octane rating

A

comparison of the anti-knock quality of a gasoline with that of pure isooctane, which has a rating of 100

50
Q

catalytic reforming

A

a process that converts straight-chain alkanes to aromatic hydrocarbons

51
Q

synthesis gas

A

a mixture of carbon monoxide and hydrogen gas used for organic synthesis

52
Q

nuclear reactor

A

a power plant that produces electricity using nuclear fission reactions

53
Q

breeder reactor

A

a nuclear reactor that converts nonfissionable isotopes to nuclear fuel; most commonly, uranium-238 is converted to plutonium-239 by neutron bombardment

54
Q

advantages of nuclear energy

A
  • plants do not add to the greenhouse effect
  • plants do not add air pollutants to the atmosphere
  • it lowers trade deficits
  • way more sustainable than other forms of energy
55
Q

disadvantages of nuclear energy

A
  • elaborate/expensive safety precautions must be taken in & around plants
  • fear of potential nuclear power plant meltdown
  • requirement of storing & isolating highly radioactive fission products for centuries
  • production of thermal pollution
56
Q

explain how nuclear reactors work

A

fission of uranium heats the water in the reactor, which generates steam that drives the turbines, producing electricity. Control rods absorb neutrons to slow the fission reaction as needed.

57
Q

photovoltaic cell (solar cell)

A

a cell that uses semiconductors to convert sunlight directly into electrical energy

58
Q

biomass

A

dry plant material used as fuel

59
Q

biomass

A

dry plant material used as fuel

60
Q

geothermal energy

A

energy derived from the heat of Earth’s interior

61
Q

fuel cell

A

an electrochemical cell that produces electricity directly from continuously supplied fuel and oxygen

Chemistry (9 decks)

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