Phase Changes Phase Changes Any time the state of matter changes, Any time the state of matter changes, intermolecular forces are “created or intermolecular forces are “created or destroyed” destroyed” This requires energy (think temperature or This requires energy (think temperature or pressure). pressure).
19
Embed
Phase Changes Any time the state of matter changes, intermolecular forces are “created or destroyed” This requires energy (think temperature or pressure).
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Phase ChangesPhase Changes Any time the state of matter changes, Any time the state of matter changes,
intermolecular forces are “created or destroyed”intermolecular forces are “created or destroyed” This requires energy (think temperature or This requires energy (think temperature or
pressure).pressure).
Phase ChangesPhase Changes
Evaporation Evaporation vs. Boilingvs. Boiling
Evaporation Evaporation occurs when occurs when particles at particles at the the surfacesurface of of a liquid a liquid become a gas.become a gas.
q = (m)(s)(q = (m)(s)(ΔT)ΔT) But ΔT = 0 But ΔT = 0
during a during a phase changephase change
Heat (q) is still Heat (q) is still being added being added so a different so a different equation is equation is needed….needed….
Phase Changes & ThermoPhase Changes & Thermo q = (moles of substance)(q = (moles of substance)(ΔΔHHphase changephase change)) How much energy does it take to How much energy does it take to
change 54.0 g of ice to liquid water?change 54.0 g of ice to liquid water?
Phase Changes & ThermoPhase Changes & Thermo
54.0 g 54.0 g HH22OO 18.0 g 18.0 g
HH22OO
1 mol 1 mol HH22OO = 3.00 mol = 3.00 mol
HH22OO
• First, find the moles of water:First, find the moles of water:
Phase Changes & ThermoPhase Changes & Thermo Then, plug into the equation to solve:Then, plug into the equation to solve: q = (3.00 moles)(6.01 kJ/mol)q = (3.00 moles)(6.01 kJ/mol) q = 18.0 kJ of energyq = 18.0 kJ of energy
Phase Changes & ThermoPhase Changes & Thermo
What if the temperature What if the temperature changes changes andand the phase the phase changes?changes?
Example:Example: How much energy does it take How much energy does it take
to melt 108 g of ice an heat it to melt 108 g of ice an heat it to a temperature of 50.0to a temperature of 50.0ooC?C?