Chemistry 30-1: Chapter 11

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scientific perspective

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43 Terms

1

scientific perspective

research, explaining natural phenomena

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2

technological perspective

development and use of machines, instruments and processes that have a social purpose

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3

ecological perspective

relationship between living organisms and the environment

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4

economic perspective

production distribution and consumption of goods/wealth

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5

political perspective

involves vote and getting actions/measures

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6

STEEP

  • scientific, technological, economical, ecological, political perspectives

  • ways to approach societal issues in science and technology

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7

energy

  • the ability to do work

  • can be transformed from one form to another

  • direction of flow determines wether it is exothermic or endothermic

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8

first law of thermodynamics

during and energy transfer, the total energy of a system remains constant

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9

2nd law of thermodynamics

enery will flow from hot to cold until thermal equilibrium is reached (substance and environment - usually water - are the same temp)

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10

endothermic

  • energy is absorbed

  • feels cool

  • separates bonded particles (↑ potential energy)

ex. ice pack

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11

exothermic

  • energy is given off

  • feels warm

  • bonds particles together ( ↓ potential energy)

ex. hot pack

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12

sources of energy

  • chemical - fossil fuel, food

  • nuclear - uranium, plutonium, hydrogen

  • solar - radiant energy, UV radiation

  • geothermal - hot springs, geysers, volcanoes

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13

what is the origin of chemical energy

the sun (radiant energy)

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14

how the sun transfers energy throughout the biosphere?

sun → photosynthesis → cellular respiration → biological decay → formation of fossil fuels → combustion → release of stored energy

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15

photosynthesis

  • carbon dioxide and water react in plant in the presence of sunlight to produce glucose and oxygen

  • endothermic reaction

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16

cellular respiration

  • glucose is stores are accessed from photosynthesis

  • glucose and oxygen react to form carbon dioxide, liquid water and energy

  • exothermic reaction

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17

hydrocarbon combustion

  • the burning of fossil fuels

  • water vapor is formed in this type of reaction

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18

chemical change

  • reactants have different chemical compositions than the products

  • rearrangement of molecules

  • involves a change in temperature (exo or endothermic)

  • total potential energy of reactants is different than the products due to different chemical compositions

ex. combustion, neutralization, decomposition, formation

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19
<p>endothermic reactionary pathway</p>

endothermic reactionary pathway

  • heat is absorbed during this type of reaction

  • change in enthalpy is positive because energy is gained

<ul><li><p>heat is absorbed during this type of reaction </p></li><li><p>change in enthalpy is positive because energy is gained</p></li></ul>
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20
<p>exothermic reactionary pathway</p>

exothermic reactionary pathway

  • heat is released during this type of reaction

  • change in enthalpy is given off because energy is lost

<ul><li><p>heat is released during this type of reaction</p></li><li><p>change in enthalpy is given off because energy is lost</p></li></ul>
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21

kinetic energy

  • energy of motion/motion due to heat

  • when molecules change in temperature the tend to speed up/slow down

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22

potential energy

  • energy stored in a position or state

  • when a chemical change in phase or change in chemical composition (chemical rxn occurs) there is a change in this type of energy

  • chemical changes release more energy that phase changes

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23

intermolecular bonds

  • bonds between molecules

  • relatively weak bonds (release less energy)

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24

intramolecular bonds

  • bonds between elements within molecules

  • relatively strong bonds (release more energy)

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25

calorimetry

  • the process used to measure the changes in enthalpy (heat energy)

  • measured in joules (J) or kilojoules (KJ)

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26

specific heat capacity

the amount of energy (J) required to change 1.00g of a substance by 1.00 degrees celsius

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27

thermal energy (Q)

  • the total kinetic energy of a substance

  • measured by Q = mct

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28

what is the density of water

  • 1ml = 1g

  • 1L = 1kg

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29

thermochemistry

  • the study of energy changes by a chemical reaction during a chemical reaction

  • energy changes occur by energy being absorbed from or released to the surroundings

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30

enthalpy

heat energy of a system

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31

calorimeter

  • an instrument used to measure the amount of energy lost or absorbed during a phase change or chemical reaction

  • by knowing how much energy water gains or loses, we can determine the energy lost or absorbed by the substance

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32

simple calorimeter

  • used primarily for phase changes

  • basic requirements include:

    • measured amount of liquid (water)

    • thermometer

    • isolated system

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33

metal can calorimeter

  • usually for reaction that involve temperatures > 100 degrees celsius

  • you cannot assume this type of calorimeter is an isolated system because heat energy is transferred to both the water and the container

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34

bomb calorimeter

  • usually for volatile combustion reactions

  • it is more precise and contains fixed components

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35

what does an increase in a calorimeters water temperature indicate?

  • release of energy by the system

  • increase of heat

  • exothermic reaction

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36

what does a decrease in a calorimeters water temperature indicate?

  • absorption of energy by the system

  • decrease of heat

  • endothermic reaction

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calorimetry assumptions

  • system is isolated - all energy lost or gained by the chemical system is gained by the calorimeter

  • conservation of mass - all material (ie. mass) of the system is conserved

  • specific heat capacity of water over a temperature range remains @ 4.19J/g degrees celsius

  • specific heat capacity of dilute solutions is 4.19 J/g degrees celsius

  • density of solute is the same as water

  • thermal energy lost/gained by the rest of the calorimeter is negligible

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38

efficiency

  • the ratio of useful energy produced (energy output) to energy used in its production (energy input) in % form

  • efficiency = energy out/energy in x 100%

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39

what does a positive enthalpy indicate?

  • endothermic reaction

  • energy is gained by the chemical system

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40

what does a negative enthalpy indicate?

  • exothermic reaction

  • energy is lost by a chemical system

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41

molar enthalpy

the enthalpy change per one mole of a substance

H = Hm x n

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42

neutralization calorimetry

  • the surroundings of the calorimeter becomes the combination of the volumes of the two solutions

  • solutions are dilute meaning they have the same density as water

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43

metal can calorimetry

  • some problems involve containers which absorb energy as well as the solution that the substance is placed in

  • in these types of calorimeters, you need to calculate the energy absorbed by the container in addition to the solution

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