Chemistry Chapter 15.2 Heat
in thermochemistry what is the system
specific part of the universe that contains the reaction you wish to study
define thermochemisty
study of heat changes that accompany chemical reactions and phase changes
define universe
system plus surroundings
what can u use calorimeter for
to determine the specific heat of an unknown metal
what is impossible to know
total energy content of a substance
can u measure change in enth
yes
When Hreactants is subtracted from the smaller Hproduvrs what happens
A negative value for Hrxn results
When Hreactanrs is subtracted from larger Hproducts what happens
A positive value for Hrxn results p
What is data to be collected in a calorimeter
Change in temperature of the mass of water
How does heat flow
From surroundings to system
Enthalpy changes for and exothermic reaction are always what
Negative
Can you actually meSure the actual energy of enthalpy of a substance
No
Why are calorimeters open to the atmosphere
So reactions carried out in them occur at constant pressure
What is impossible to know
Total energy content of a substance
data to be collected in calorimeter is what
change in temperature of this mass of water
define enthalpy of a reaction
chnge in enthalpy of a reaction
what equation is delta Hrxn defined as
delta Hrxn= Hproducts=Hreactants
what is delta Hrxn
difference between the enthalpy of the substances that exist at the end of the reaction and the ehtalpy of the substances present at the start
What is the enthalpy change for a reaction
enthalpy of the products minus the enthalpy of the reactants
define surroundings
everything in the universe other than the system
total amount of energy a substance contains depends on what
factors that aren't completely understood
what happens in an endothermic reaction
flow of heat is reversed
why us measure in change in tenth
heat absorbed or released in chemical exaction
define enthalpy
heat content of a system at constant pressure
define calorimeter
insulated device used for measuring the amount of heat absorbed or released during a chemical reaction
what is placed in an insulated chamber to absorb the energy released from the reacting system
known mass of water
can you measure actual energy or entalhoy of a substance
no
when does the flow of heat stop
only when the temperature of metal and water are equal
some products have been engineered to what
produce heat on demand
burning of fuels always does what
produces heat
energy released ir ekveked from reactions carried out at constant pressure is given what symbol
qp
every chemical reaction and change of physical state either what or what
releases or absorbs heat
