Energy Curve POGIL

Energy Curve POGIL
Below is a diagram showing a typical heating/cooling curve for water. It reveals a wealth
of information about the structure and changes occurring in water as it is heated or cooled
through all three phases of matter at different temperatures. At the top of the diagram are
pictures representing the typical particle arrangement as substances change through their states.
(Endothermic)
Heat removed (Exothermic)
Identify by letters (A-E) in which section the following are found:
1._____ Solid getting warmer 10._____ Particles are rigid & compressed
2._____ Liquid getting warmer 11._____ Particles closest together
3._____ Gas getting warmer 12._____ All particles able to move past each
4._____ Freezing/ Solidifying other in fluid motion
5._____ Melting/ Liquefying 13._____ Condensation occurs
6._____ Boiling point 14._____ Strongest IMF
7._____ Boiling (Vaporization) 15._____ Particle motion is stationary
8._____ Particles farthest apart 16._____ Particles are most chaotic and
9._____ Weakest IMF disordered. Have the most entropy.
Answer the following questions based on the energy curve below.
Heating / cooling curve for water
 Heat removed
1. Is boiling an exothermic or endothermic process? ______________________
2. Is freezing an exothermic or endothermic process? ____________________
3. Is melting an exothermic or endothermic process? ____________________
4. When heat energy is released from the system, what physical change occurs at D?
________________________
5. When heat energy is released from the system, what physical change occurs at B?
_________________________
6. When heat energy is added to the system, what physical change occurs at B?
________________________
7. During which interval(s) is the KE increasing (KE is energy of motion…think, what is
the relationship between energy, temperature and motion? _________________
8. During which interval does the substance have the weakest IMF? _______________
9. During which interval does the substance have strongest IMF? __________________
10. If the particles are not moving faster (temperature is not increasing) during B & D, then
what is the energy absorbed for? ____________________________________________
Now try to answer questions for a substance that is NOT water. At Standard Pressure: 101.3kPa
I II III IV V
1) What is the normal melting point temperature of the substance? _______________

2) What is the normal boiling point of the substance? ________________________
3) What physical process occurs during interval II in the endothermic direction? ____________
4) What physical process occurs during interval IV in the exothermic direction? _____________
The following graph represents the cooling curve for a substance in the gaseous state and becomes solid
as heat energy is released.
1. What is the solidification point temperature of this substance? ______________

2. During which time interval is the substance solidifying? __________________
3. What is the freezing point for this substance? _____________
4. During which time interval is the substance condensing? ____________________
NOW Another way to diagram phase changes is with a triple point graph. These graphs are
often not drawn to scale, SHADE IN the three areas that correspond to the three different states
of matter. THEN answer the questions that follow.
1. At 5.1atm and -56.7oC what states of matter are present? ___________________

2. At 6 atm and 30oC what state is the substance? ___________________
3. At 60atm and room temperature, what state of matter is the substance? _____________
4. At 101.3kPa (1atm) and -90oC what physical change happens when the temperature is
increased to 20oC? __________________
5. At 150kPa ( _____ atm?) and -60oC what state of matter is the substance? _________
6. What state is the substance at 100kPa (_____ atm?) and 285K ( ______ oC?)? ________
Standard Pressures Standard Temperature

(measured at sea level) 0oC
273K
101.3kPa
760 mmHg o
C + 273 = K
760 Torr
1.0 atmospheres (atm)
At standard temperature and pressure, bromine (Br 2) is a red liquid. The phase diagram of
bromine is shown below. Use this diagram for questions that follow.
1. Label each region as solid, liquid or gas.

2. Label the triple point, normal melting point (at standard pressure) and normal boiling point (at
standard pressure) and estimate their values.
3. What is the boiling point of bromine when the pressure is 75kPa?
4. On the graph, label the portions where sublimation, vaporization and melting could occur at
different pressures.
5. In high altitude areas of the world, there is less atmospheric pressure, would this change increase,
decrease or cause the boiling point of bromine to remain the same?
Circle the correct answer in parenthesis.

6. Bromine vapor at 15oC ( condenses sublimes ) when pressure is raised to 50kPa.
7. Bromine liquid at 70kPa ( vaporizes freezes ) when the temperature is decreases to -15oC.

Energy Curve POGIL

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Energy Curve POGIL

Identify by letters (A-E) in which section the following are found:

Heating / cooling curve for water

1) What is the normal melting point temperature of the substance? _______________

1. What is the solidification point temperature of this substance? ______________

1. At 5.1atm and -56.7oC what states of matter are present? ___________________

Standard Pressures Standard Temperature

1. Label each region as solid, liquid or gas.

Circle the correct answer in parenthesis.

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