Catalyst1. Define endothermic. Give an example.2. Define exothermic. Give an example3. 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/condensation

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.

Vaporization

Condensation

Melting/Fusion

Freezing

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

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 AssessmentRate yourself 1 – 4 on LTs 7.3, 7.4, and 7.5

Exit Slip1. 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 AssessmentRate 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