Unit Three Flashcards
How do hot and cold packs work?
Hot packs- chemical reaction that releases energy (exo)
Cold packs- chemical reaction that takes in energy (endo)
What is the x and y axis on a heating and cooling curve
Temp is y
Time/ heat added is x
What is the opposite of sublimation
Deposition
What is the opposite of vaporization
Condensation
What is the opposite of fusion
Solidification
What are the x and y on phase diagrams
X axis is temp
Y axis is pressure
What is the critical point
Temp at which it is impossible to liquefy the substance no matter pressure
What is triple point
Where all three phases are at equilibrium, same temp and pressure
At constant temp what would you do to cause a substance to change from liquid to solid
Increase pressure
If it’s not a phase change, it’s a
Temperature change
Thermochemistry
The study of energy changes associated with chemical reactions
Heat
The transfers of thermal energy between two bodies at different temps
Thermal energy
Energy associated with random movement of atoms of molecules
System
The specific part of the universe that one is studying
Surroundings
The rest of the universe, everything but the system
Universe
The combination of the item under investigation and the immediate factors that can influence it
Universe=
System plus surroundings
Types of systems
Open, closed, isolated
Open system
Allows transfer of both energy and mass
Closed system
Energy can leave but mass can not
Isolated system
Mass not energy transfer can happen ( no such thing)
Enthalpy (H)
Is the total energy of a system, some of which is stored as chemical energy in the chemical bonds
T or F energy absorbed from broken bonds never equal that released in making new bonds
T
Exothermic
Release more energy put in
Endothermic
More energy put in than our
Triangle H is
Heat given off or absorbed during reaction, H products- H reactants
Released has + or - energy
Negative
Calorimetry
The temp of a liquid inside a well insulated container (calorimeter) is measured before and after a reaction
Specific heat capacity
The amount of energy required to raise the two of one gram of a substance by one degree
Water specific heat
4.18j/g•c
Density of water is
One gram equals one milliliter
Sublimation
Unusual phase change, specific process occurs when a solid goes directly into a gas without going through the liquid phase
Ex dry ice, carbon dioxide
Deposition
Solid formed directly from vapor, same heat added same as sublimation except negative
Why does it take more heat to boil water rather than melt ice
The attraction is stronger between a solid and liquid. Takes more energy because molecules are more spread out in boiling
What is the formula for phase changes
Q= mol* triangle H
What is the formula for solid/liquid/gas
Q=mc triangleT
Triangle H units
Kj/mol
