Energy Review
Matching – Choose the answer which best fits the description.
A. FreezingF. Boiling
B. CondensationG. Potential Energy
C. MeltingH. Kinetic Energy
D. DepositionI. Sublimation
E. STPJ. Evaporation
_____1. The change of a gas directly to a solid
_____2. Vaporization that occurs throughout a liquid being heated
_____3. A liquid changing to a solid
_____4. A solid changing to a liquid
_____5. Energy of motion
_____6. Gas changing to a liquid
_____7. The change of a solid directly to a gas
_____8. Stored energy; energy of position
_____9. The conversion of a liquid to a gas at the surface of a liquid that is not boiling
_____10. Standard temperature (0°C) and pressure (1 atm)
Convert Calories and Joules Use the fact that 1 calorie = 4.184 J to help you convert the following:
11. Convert 515.76 cal to joules
12. Convert 293. kcal to joules
13. Convert 250.05 cal to kilojoules
14. Convert 1.30 J to cal
15 Convert 7.56kJ to kcal
Problems Solve each specific heat or latent heat problem below. Show all work, units, and labels.
16. How much energy is needed to heat 49.2 g of acetic acid, CH3COOH, from 24.1 oC to 67.3oC? (Cp of acetic acid = 2.043 J/goC)
17. If a sample of ethanol, CH3CH2OH, requires 1299.04 J of energy to raise its temperature from 19.6oC to 75.0oC, what is the mass of the sample? (Cp of ethanol = 2.44 J/goC)
18. If 2.47 g of sand is heated with 21.2 J of heat energy, what temperature change would we expect? (Cp of sand = 0.290 J/goC)
19. How many joules of energy are needed to melt 54 grams of ice at its melting point? Assume that the molar heat of fusion of ice is 6 kJ/mol.
20. How many joules of energy are needed to boil 90 grams of water at its boiling point. Assume that the molar heat of vaporization of water is 41 kJ/mol.
21. A 31.9 g sample of calcium sulfate (CaSO4) at 83.2oC is cooled and loses 240 cal (use -240 for Q) of energy. What is the final temperature of the calcium sulfate sample? (Cp of CaSO4 = 0.27 cal/goC)
22. How much energy is required to melt 4 moles of ice at its melting point? Assume that the molar heat of fusion of ice is 6 kJ/mol.
23. How much energy is required to boil 4 moles of water at its boiling point? Assume that the molar heat of vaporization of water is 41 kJ/mol.
24. If a 45.6 g bar of a metal at 23.0oC absorbs 3500 J of heat until the temperature reaches 53.0oC, then what is the specific heat of the metal?
25. How many calories are given off when 50 g of water at 0oCfreezes? (ΔHfus = 79.72cal/g)
Refer to the phase diagram below when answering the questions:
1)On the diagram, label the following: Solid, liquid, gas/vapor, triple point, critical point
2)What is the normal boiling point of this substance (at 1 atm)? ______
3)What is the normal freezing point of this substance (at 1 atm)? ______
4)If I had a quantity of this substance at a pressure of 1.25 atm and a temperature of 3000 C and lowered the pressure to 0.25 atm, what phase transition(s) would occur?
5)At what temperature do the gas and liquid phases become indistinguishable from each other?
The graph below represents the heating curve of a substance that starts as a solid below its freezing point.
Label the following with the indicated letters:
A – Melting/Freezing point
B – Boiling/Condensation point
Label when the substance is a: Solid, Liquid, Gas, Liquid ↔ Gas, Liquid ↔Solid
What is the melting and freezing point of this substance? Write a temperature
What is the boiling and condensing point of this substance? Write a temperature