Honors Chemistry Chapter 17 - Thermochemistry

thermochemistry

the study of energy changes that occur during chemical reactions and changes in state

chemical potential energy

the energy stored in the chemical bonds of a substance

heat

energy that transfers from one object to another because of a temperature difference between the objects; represented by q

system

the part of the universe on which you focus your attention

surroundings

everything else in the universe

law of conservation of energy

in any chemical or physical process, energy is neither created nor destroyed

endothermic process

when heat is absorbed from the surroundings

exothermic process

releases heat to its surroundings

heat capacity

the amount of heat needed to increase the temperature of an object exactly 1 degree Celsius; depends on both its mass and its chemical composition

specific heat

the amount of heat it takes to raise the temperature of 1g of the substance 1 degree Celsius

calorimetry

the measurement of the heat flow into or out of a system for chemical and physical processes

calorimeter

the insulated device used to measure the adsorption or release of heat in chemical or physical processes

enthalpy

accounts for the heat flow of the system at constant pressure

thermochemical equation

a chemical equation that includes the enthalpy charge

heat of reaction

the enthalpy change for the chemical equation exactly as it is written

molar heat of fusion

the heat absorbed by one mole of a solid substance as it melts to a liquid at a constant temperature

molar heat of solidification

the heat lost when one mole of a liquid substance solidifies at a constant temperature

molar heat of vaporization

the amount of heat required to vaporize one mole of a given liquid at a constant temperature

molar heat of condensation

the amount of heat released when one mole of a vapor condenses at its normal boiling point

molar heat of solution

the enthalpy change caused by the dissolution of one mole of substance

Hess’ law of heat summation

if you add two or more thermochemical equations to give a final equation, then you can also add the heats of reaction to give the final heat of reaction

standard heat of formation

the change in enthalpy that accompanies the formation of one mole of a compound from its elements with all substances in their standard states

energy

the ability to do work

work

force x distance

types of energy

1. heat

2. kinetic

3. potential

4. chemical potential (stored in chemical bonds)

fission

splitting atom

fusion

combing H+ + H+ = He

energy has neither

mass nor volume

energy is only detected because of

its effects

energy changes occur as either

heat transfer, or work, or a combination of both

heat flows spontaneously from a

warmer object to a cooler object

chemical reactions and changes in physical state generally involve either

the adsorption or the release of heat

example of a system

beaker

together, the system and its surroundings make up

the universe

During any chemical or physical process, the energy of the universe

remains unchanged

If the energy of the system increases, the energy of the surroundings

must decrease by the same amount

entropy

disorder

the entropy of the universe is…

always increasing

a perfectly crystalline solids at absolute zero has an

entropy of zero

examples of endothermic reactions

AC, refrigerator, sit by fire

examples of exothermic reactions

body releasing heat, freezing, running

calorie (cal)

the quantity of heat needed to raise the temperature of 1g of pure water at 1 degree Celsius

calorie is written with a small c except when

referring to the energy contained in food

the heat capacity of an object depends on

mass, chemical composition, physical state

the greater the mass,

the greater the heat capacity

water has a very high

specific heat

metals generally have

low specific heats

the heat absorbed or released by a reaction at constant pressure is the same as

the change in enthalpy symbolized as delta H

the sign of delta H is positive for an ————— and negative for an ——————-

endothermic reaction; exothermic reaction

what is the standard state of a substance

25 degrees Celsius, 101.3 kPa, 1 atm