Chapter 15 - Energy & Chemical Change

an insulated device used for measuring the amount of heat absorbed or released during a chemical or physical process

Calorimeter

the ability to do work or produce heat.

energy

the amount of energy released as heat when one mole of a substance undergoes complete combustion (burning) under standard conditions

enthalpy (heat) of combustion

the specific part of the universe that contains the reaction or process you wish to study

System

energy that is in the process of flowing from a warmer object to a cooler object.

heat

the amount of heat required to vaporize one mole of a liquid at its boiling point

molar enthalpy (heat) of vaporization

The energy stored within the chemical bonds of a substance

Chemical potential energy

SI unit of energy and of heat

joule

the amount of energy, in the form of heat, required to convert one mole of a substance from a solid to a liquid phase at its melting point

molar enthalpy (heat) of fusion

the amount of heat required to raise the temperature of one gram of that substance by one degree Celsius.

Specific heat

The change in enthalpy that occurs during a chemical reaction at constant pressure

Enthalpy (heat) of reaction

the total energy of an isolated system remains constant

Law of conservation of energy

amount of energy required to raise the temperature of one gram of pure water by one degree Celsius (1°C)

Calorie

focuses on the energy exchange between a system and its surroundings in the form of heat

Thermochemistry

Everything in the universe other than the system

Surroundings

a balanced chemical equation that displays the magnitude of the enthalpy value associated with the process

thermochemical equation

the system plus the surroundings

Universe

the heat content of a system at constant pressure.

Enthalpy

A slice of pizza has 300 Cal. Convert this energy to joules.(1 Cal=1000 cal, one calorie equals 4.184 joules)

1,255,200 J

Convert 250 Cal of chocolate to joules. (1 Cal=1000 cal, one calorie equals 4.184 joules)

1,046,000 J

Kinetic or potential energy? A roller coaster at the top of a hill

potential

Kinetic or potential energy? A flying bird

kinetic

Kinetic or potential energy? A rolling basketball

kinetic

Kinetic or potential energy? Water behind a dam

potential

Kinetic or potential energy? A speeding train

kinetic

q = c x m x ΔT c= specific heat m= mass How much heat is absorbed when 40.0 g of ethanol is warmed by 22.0°C? (c = 2.44 J/(g·°C))

2147.2 J

q = c x m x ΔT c= specific heat m= mass How much heat would be absorbed by 20.0 g of aluminum when its temperature is increased by 15.0°C? Use the specific heat of granite, 0.647 J/(g.°C).

194.1 J

ΔT is the change in temperature in *C, or Tfinal-Tinitial. A metal rod cools from 100°C to 25°C. What is ΔT?

-75

ΔT is the change in temperature in *C, or Tfinal-Tinitial. A pot of water is heated from 20°C to 80°C. What is ΔT?

60

If ΔH is positive is this reaction endothermic or exothermic?

endothermic

If ΔH is positive does it absorb or release heat?

absorb

If ΔH is negative, is this reaction endothermic or exothermic?

exothermic

If ΔH is negative does it absorb or release heat?

release

When ethanol changes from liquid to gas, the ΔH is 38.6 kJ/mol. If ethanol changes from gas to liquid, what would the ΔH be?

-38.6

How much energy is released when 2.5 moles of octane is burned? (ΔHcomb= -5471kJ/mol)

13,677.5 kJ