Catalyst
1. Define endothermic. Give an example.
2. Define exothermic. Give an example
3. I cool a glass of water, is this an
endothermic process or an exothermic
process?
End
Lecture 7.2 – Heating Curves and
Phase Diagrams
Today’s Learning Targets
• 7.3 – I can draw a phase diagram to describe how
pressure and temperature are related and discuss what a
triple point is.
• 7.4 – I can analyze and draw a heating curve to describe
how energy is lost or gained while a substance changes
phases. I can identify on the graph the Hfusion and the
Hvaporization.
• 7.5 – I can describe a reaction using the ideas of enthalpy
and entropy.
Today’s Focus Question
• How much energy is required to turn my
Flamin’ Hot Cheetos into a liquid?
What are enthalpy and entropy?
I. Enthalpy (ΔH)
• Enthalpy is a measure of
the total energy that a
system has.
• Amount of energy
released or absorbed
during a
process/reaction.
• Measured in kilojoules
(kJ)
II. Entropy (ΔS)
• The universe tends towards disorder.
• Entropy is the measurement of the
randomness or disorder of a system.
• More energy = more disorder
• Measure in J/K
How are enthalpy and phase
changes related?
I. ΔHfusion and ΔHvaporization
• Large amount of energy that is required to change
phases
• ΔHfusion = Energy to change solid to a liquid.
• ΔHvaporization = Energy to change liquid to a gas.
• ΔHfreezing = Energy to change liquid to a solid
• ΔHcondensation = Energy to change gas to a liquid
II. Heating Curves
• Heating curves are graphs of the relationship
between temperature and time.
• Allow us to identify important values
ΔH of
vaporization/condensat
ion
ΔH of fusion/freezing
Summarize
Justify – TPS
• Why was the water able to boil at room
temperature when we dropped the pressure?
How are pressure temperature
and phase related?
I. Pressure and Temperature
• The state of matter of a substance depends on
both the temperature and pressure
• A phase diagram is a graph temperature,
pressure, and phase for a substance
•
II. Important Points on a Phase
Diagram
Triple Point – The
temperature and
pressure conditions at
which the solid, liquid,
and gas phases of a
substance coexist
• Critical Point – The
temperature and
pressure at which the gas
and liquid state become
identical and form one
phase.
Melting/Fusion
Freezing
Vaporization
Condensation
Sublimation
Deposition
Class Example
• You have a solid at a pressure of 30 atm and -15
oC, if you decrease the pressure at constant
temperature, what phases will the substance go
through?
Table Talk
Stop and Jot
• Atmospheric pressure on Mt. Everest is 0.29
atm. What is the boiling point of water there
using the phase diagram below.
Summarize
Vocab Direct Instruction Assignment
• With our group, let’s
do some vocab
definitions!
• Make a power point
defining each of these
•
terms:
•
• Enthalpy
•
• Entropy
•
• Δhfusion
•
• Δhvaporization
• ΔHfreezing
for each vocab word with
a picture, title, and a
definition!
Δhcondensation
Heating curves
phase diagram
Critical Point
Triple Point
Collaborative - Let’s Heat Some Water!
• With the table complete the heating curve lab
activity.
• Heat the ice until it reaches a rolling boil
• Show Mr. Astor when you are done
Independent Work Time
Complete the phase diagram homework you
picked up when you came in.
Learning Log Assessment
Rate yourself 1 – 4 on LTs 7.3, 7.4, and 7.5
Exit Slip
1. What is entropy?
2. Draw a basic heating curve. Have temperature on
the y-axis and heat added on the x-axis. Label
solid, liquid, gas, boiling, and freezing.
3. What is the triple point on the graph below?
Learning Log Assessment
Rate yourself 1 – 4 on LTs 7.3, 7.4, and 7.5
Closing Time
• Homework 7.2 due Monday/Tuesday
• Rough Draft Due Monday/Tuesday
• Quiz on Cheetos lab Monday/Tuesday