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25 Cards in this Set
- Front
- Back
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energy
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the ability to do work or produce heat
2 basic forms: - PE (potential energy - KE |
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potential energy
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energy due to the composition or position of an object
potential energy of a substance depends upon: - its composition - the type of atoms in the substance - the number and type of chemical bonds joining the atoms - the way the atoms are arranged |
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law of conservation of energy
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in any chemical reaction or physical process, energy can be converted from one form to another, but it is neither created nor destroyed
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chemical potential energy
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the energy stored in a substance b/c of its composition
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heat
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(q)
the energy that is in the process of flowing from a warmer object to a cooler object measured through the flow of energy and the resulting change in temp |
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calorie
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(cal)
a measurement of heat (metric) Def: the amount of heat required to raise the temp of 1 g of pure water by 1 degree Celsius 1 (nutritional) Calorie = 1,000 cal or 1 kcal |
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joule
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(J)
the SI unit of heat and energy 1 cal = 4.184 J |
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specific heat
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(of any substance) the amount of heat required to raise the temp of that substance by 1 degree Celsius
Unit: J/(g degrees C) each substance has its own specific heat b/c different substances have different compositions |
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q (heat absorbed or released) =
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q = c X m X change in temp
c = specific heat of substance m = mass of substance (g) change in temp = Tfinal - Tinitial (degrees C) |
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calorimeter
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an insulated device used for measuring the amount of heat absorbed or released during a chemical or physical process
- reactions occur at a constant pressure |
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thermochemistry
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the sutdy of heat changes that accompany chemical reaction and phase changes
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system
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the specific part of the universe that contains the reaction or process you wish to study
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surroundings
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everything in the universe other than the system
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universe
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the system + the surroundings
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enthalpy
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(H)
the heat content of a system at constant pressure - you can't measure the actual energy or enthalpy of a substance, but you can measure the change in enthalpy |
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enthalpy (heat) of reaction
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the change in enthalpy for a reaction-- the heat absorbed or released in a chemical reaction
= Hproducts - Hreactants AND = Hfinal - Hinitial |
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endothermic
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process in which the system ABSORBS thermal energy from the surroundings
products have more energy than reactants change Hrxn is positive energy added is in the REACTANTS |
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exothermic
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process in which the system RELEASES thermal energy to the surroundings
products have less energy than the reactants change Hrxn is negative energy added is in the PRODUCTS |
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endergonic
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process in which the system ABSORBS energy (not neccessarily thermal) from the surroundings
energy added is in the REACTANTS |
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exergonic
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process in which the system RELEASES energy (not necessarily thermal) to the surroundings
energy added is in the PRODUCTS |
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thermochemical equation
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a balanced chemical equation that includes the physical states of all reactants and products and the energy change, usually expressed as the change H
nature of reaction can be written as subscript of change H |
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enthalpy (heat) of combustion
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the enthalpy change for the complete burning of one mole of the substance
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standard conditions
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1 atm pressure
298 K (25 degrees C) indicated by the 0 superscript on changes in enthalpy |
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molar enthalpy (heat) of vaporization
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the heat require the vaporize 1 mole of a liquid
endothermic-- positive for water: = 40.7 kJ/mol values for condensation are the same but with opp sign |
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molar enthalpy (heat) of fusion
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the heat required to melt one mole of a solid substance
endothermic--positive for water: 6.01 kJ/mole values for solidification are the same but with opp sign |
