States of Matter Review key by mC7asl


									Chemistry                                                   Name
States of Matter Worksheet

1. Explain why there are no negative numbers on the Kelvin Scale.
       Kelvin is based on absolute zero which is 0K. No energy exists at zero Kelvin, therefore
   there are no negative numbers.

2. Liquid A has a vapor pressure of 7.37 kPa at 400C. Liquid B has a vapor pressure of 19.04
   kPa at 400C. If these liquids are the same atmospheric pressure, which would evaporate
   faster? Explain.
       Vapor B will evaporate faster because it has a larger equilibrium vapor pressure. This
   means that more of vapor B exists as a gas at the same temperature as gas A.

3. The boiling point of water in city A is 94oC; in city B it is 97oC. Which city is at the higher
   elevation? Why?
       City A is at higher BP. Air pressure is lower at higher elevation therefore there is a lower
   boiling point.

4. Explain why it would be difficult to hard-boil an egg at the top of a mountain.
       It will require a longer time to hard boil the egg due to the lower temperature of the
   boiling point at higher elevation.

5. Two beakers on a laboratory bench each contain a mixture of ice and water. Three ice
   cubes are added to one beaker and 10 mL of hot water are added to the other beaker. The
   contents of each beaker remain at their original temperature.
      Ice water is zero degree Celsius. Adding more ice will not lower the temperature. All the
   water will need to freeze before the temperature can be lowered.

      Adding hot water will not raise the temperature. It will only melt more ice. The
   temperature will not increase until the ice metls.

6. Make each statement completely true.
   a. We can measure the increase in kinetic energy in a substance by measuring how much
      its temperature has increased.

   b. The atmospheric pressure is 760 mmHg. (at sea level)

   c. In general, ionic solids have low melting points. (high melting points)

   d. The temperature of a glass of ice water will continue to rise as heat is applied.

                       Once all the ice has melted
7. Explain why polar liquids are slower to evaporate than nonpolar liquids.

       Polar liquids have stronger intermolecular forces. Therefore will evaporate at a lower

8. Use the kinetic molecular theory to explain each of the following phenomena:
   a. A strong smelling gas released from a container in the middle of a room is soon detected
      in all areas of that room.
   Gas particles are always in motion therefore they will diffuse and mix with the surrounding

   b. As a gas is heated, its rate of effusion through a small hole increases if all other factors
      remain constant.
             The heating of the gas makes the particles move faster. Thus more collisions
             with the walls of the container will increase the odds that the gas will collide with
             the opening and effuse.

9. A typical ice cube has a volume of about 16.0 cm3. Given that the density of ice at 00C is
   0.917 g/mL and the molar enthalpy of fusion of ice is 6.009 kJ/mol:
   a. Determine the mass of the ice cube.
               DxV=m         0.917g/mL x 16.0 cm3 = 14.7g

   b. Determine the number of moles of H2O present in the sample.

   14.7g x 1mole/18.02g H2O = .816 moles

   c. Calculate the amount of energy needed to melt the ice cube.

   0.816 moles x 6.009 kJ/mol = 4.90kJ

10. The molar enthalpy of vaporization of water if 40.79 kJ/mol, and the molar enthalpy of fusion
    of ice is 6.009 kJ/mol. How much energy is absorbed when 30.3 g of liquid water boils?

   30.3g x 1 mole/18.02g H2O x 40.79 kJ/mol = 68.6 kJ (endothermic)

11. How much energy is needed to condense 10.0 grams of steam into water? Use the
    enthalpies of H2O given problem 10.

   10.0g x 1 mole/18.02g x -40.79kJ/mol = -22.7kJ (negative because this is exothermic)
Interpreting Phase Diagrams



                                               A, M
           Pressure (kPa)

                                                                       B, V
                                        C, S


                                  -30    -10       0      20      40          60
                                                 Temperature (oC)

Figure 1-1:                  Phase diagram for bromine (Br2). Note that the scales are distorted to emphasize some
                             of the graph’s features.

At standard temperature and pressure, bromine is a red liquid. Bromine sublimes when the temperature is
-25 C and the pressure is 101.3 kPa, This does not represent bromine. Ignore

1. Label each region of the graph as solid, liquid, or vapor.

Top left is solid, top right is liquid, bottom right is gas.

2. Label the triple point, normal melting point, and normal boiling point on the graph and estimate their
   respective values in the spaces below.
                                         o                                         o                            o
Normal melting point = __~-5 C___ Normal boiling point = ___~60 C___                    Triple point = 10kPa, -4 C

3. Use the letter “A” to label the line that gives the conditions for equilibrium between solid and liquid
   phases of bromine, the letter “B” to label the curve that gives the conditions for equilibrium between
   liquid and vapor phases of bromine, and the letter “C” to label the curve that gives the conditions for
   equilibrium between solid and vapor phases of bromine.

4. Describe how the melting point of bromine changes with the external pressure. Based on the slope of
   the melting-point curve in the phase diagram, would you characterize the solid phase of bromine as
   more dense or less dense than the liquid phase of bromine?
The melting point is lower as pressure increases. This means that liquid is more dense than solid for

5. What is the boiling point of bromine when the external pressure is 75 kPa?
   About 57 C

6. Explain the significance of the triple point.
      All three states of matter exist in equilibrium.

7. Using arrows labeled “S”, “V”, and “M”, label those portions of the phase diagram where sublimation,
   vaporization, and melting occur, respectively.

Circle the correct word in the parentheses in each of the following sentences.
8. Bromine vapor at 15 C (condenses, sublimes) when the pressure is raised to 50 kPa.
9. Bromine liquid at 70 kPa (vaporizes, freezes) when the temperature is decreased to -15 C.

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