Name Date Pd
Review for Unit 2 Exam
To be best prepared for the Unit 2 Exam, make sure you have mastered the following concepts:
1. States of Matter
a. Be able to identify states of matter and the phase changes between states of matter on a heating/cooling curve.
b. Be able to describe the characteristics of solids, liquids and gases in terms of particles and their arrangements/attractions.
c. Be able to draw particle diagrams of these arrangements and attractions for solids, liquids, gases.
2. Energy
a. Define energy and describe the ways in which it is stored in a system (Eph,
Eth, Ech)
b. Draw energy bar charts to account for energy storage and transfer in all sorts of changes. Make up a sample situation and sketch the bar chart. c. Given a heating/cooling curve for a substance, identify what phase(s)
is/are present in the various portions of the curve, and what the melting and freezing
temperatures for the substance are.
d. Given a heating/cooling curve for a substance, identify which energy storage mode is changing for the various portions of the curve and how energy is stored at each portion of the curve.
e. Given a situation in which a substance at a given temperature undergoes a change (in temperature, phase or both), sketch a heating/cooling curve that represents the situation.
f. State the physical meaning of the heat of fusion (Hf) and heat of
vaporization (Hv) for a given substance. Use these factors to relate the mass of a substance to the energy absorbed or released during a phase change (at the melting or freezing temperature). Be able to do
calculations!
g. State the physical meaning of the heat capacity (Cp) of a substance and use this factor to relate the mass and temperature changes to the energy absorbed or released during a change in temperature (with no phase change). Be able to do calculations!
h. Distinguish between heat and temperature and have a general understanding of the kinetic molecular theory.
i. Have a general understanding of the first law of thermodynamics 3. The Labs
a. Understand, explain, and apply the results of the Icy Hot Lab.
b. Understand, explain, and apply the results of the Specific Heat of Metals Lab.
c. Know how to find Percent Error in a lab
The following problems should be completed as part of your review. You also should be reviewing all past worksheets/notes/readings.
1. In the Specific Heat of Metals lab your group calculated the specific heat of the metal to be 0.42 J/g°C. The actual specific heat of the metal is 0.39 J/g°C. Calculate the % error: SHOW THE CORRECT SET UP
2. List the common characteristics/traits of solids, liquids, gases in terms of particle arrangements and attractions.
3. As heat (energy) is added to a solid, liquid, or gas, what is happening at a molecular level? What about when a phase change starts to occur; what is happening to the molecules?
4. What is the kinetic molecular theory?
5. In your own words, explain what the difference is between temperature and heat.
6. List any of the formulas for this unit, label the variables, and write a quick statement for when the formula is used.
7. On a counter is a glass of water with ice cubes floating in it. You measure the temperature and find it to be 0 ˚C. Would the
temperature of the water change if you were to add more ice cubes to the glass? Explain your answer.
8. If you placed an ice tray of liquid water into a freezer, what is
happening to the kinetic energy of the water molecules? Is energy being released or gained? Explain your answer.
9. Suppose that 1500 kJ of energy were transferred to water at 20˚C.
What mass of water could be brought to the boiling point? Heat
capacity (Cp) for liquid water is 4.18 J/g˚C. (check your units)
10. Sketch an energy bar graph diagram that represents the situation in #9.
11. An ice cube (25 g) is at –8.0˚C. How much energy is required to
completely melt it? Heat capacity (Cp) for solid water is 2.10 J/g˚C,
Hf = 334 J/g. Sketch a graph of the heating curve.
12. Answer the following using the heating curve above.
a. What temp. is the freezing point of the above substance? _____ b. What is happening to the phase energy in portion “b”? _____ c. What is happening to the thermal energy in portion “b”? _____
d. What letter represents the temperature range where the solid is being heated? ___
e. What letter represents the boiling point of the above substance? ___ f. What letter represents the temperature range where the gas is being
heated?_____
g. What letter represents the melting of the solid? _____
h. What letter(s) show an increase in kinetic/thermal energy? _____ i. What letter represents condensation? _____
j. Draw what is occurring (using circles to show particle movement and spacing) and give a brief explanation about what is occurring on the particle level for the following letters.
b)
d)
13. During the Icy Hot Lab, as the water started to boil, bubbles started forming. Briefly explain what is/are inside these bubbles. (hint: think about what you are boiling and what is happening during phase change). What if alcohol was boiled? What is being formed?
14. When liquid water freezes to solid water
a. the water absorbs energy from the surroundings b. the water releases energy to the surroundings
c. the water molecules are arranged in a random pattern. d. atoms of hydrogen and oxygen recombine to form H2O.
15. Sketch an energy bar graph diagram that represents the situation in #14.
16. Sketch a temperature-time graph for the following situations below. Include labels for any phases that are present and include the correct temperatures:
a. A sample of liquid water at 50°C is cooled to -15°C.
b. A sample of solid water at -15°C is heated until half of it boils.
Quantitative Problems
Be sure to show work and label quantities. Show how units cancel. Useful constants
334 J/g Heat of fusion (Hf) (melting or freezing)
2260 J/g Heat of vaporization (Hv) (evaporating or condensing)
2.10 J/g˚C Heat capacity (c) of solid water 4.18 J/g˚C Heat capacity (c) of liquid water
17. A glass of vitamin water (140 g) cools from 75˚C and becomes frozen at 0˚C when you accidentally left it outside in a blizzard. Calculate the amount of energy that is released.
18. Suppose a bag full of ice (750 g) at 0.0 ˚C sits outside and begins to melt to liquid water. How much energy must be absorbed by the ice for all of it to melt?
19. Suppose 22000J of energy is added to 615g of an unknown substance at 20˚C. After heating, the final temperature of the substance is 87˚C. What is the specific heat of the unknown substance?
20. Supposed your frozen (-10˚C) vitamin water from question 17
was placed on a hot plate. How much energy would be required to heat the water back to room temperature (20˚C)?
