Newburyport High School - Home
Energy Curve Worksheet HONORS
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.
Identify by letters (A-E) in which section the following are found:
1. Solid getting warmer
2. Liquid getting warmer
3. Gas getting warmer
4. Freezing/ Solidifying
5. Melting/ Liquefying
6. Boiling point
7. Boiling (Vaporization)
8. Particles farthest apart
9. Weakest IMF
10. Particles are rigid & compressed
11. Particles closest together
12. All particles able to move past each other in fluid motion
13. Condensation occurs
14. Strongest IMF
15. Particle motion is stationary
16. Particles are most chaotic and disordered. Have the most entropy.
Answer the following questions based on the energy curve below.
[pic]
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
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?)? ________
At standard temperature and pressure, bromine (Br2) 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.
-----------------------
(Endothermic)
Heat removed (Exothermic)
Heating / cooling curve for water
( Heat removed
I
II
III
IV
V
Standard Pressures (measured at sea level)
101.3kPa
760 mmHg
760 Torr
1.0 atmospheres (atm)
Standard Temperature
0oC
273K
oC + 273 = K
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