Unit: Chemical Bonding

Gt Chemistry

Name: ______Date: ______MOD: ______

Properties of Water Lab

Because of intermolecular forces, water has very unique properties. It is often referred to as the universal solvent and covers about 70% of the Earth’s surface. In this lab, you will investigate some of the properties that make water so important.

OBJECTIVE

Students will be able to describe the behavior of water molecules in order to distinguish between intermolecular forces by analyzing tests of water’s properties.

MATERIALS

Gt Chemistry

Unit: Chemical Bonding

Gt Chemistry

Unit: Chemical Bonding

Two 50 mL beakers

Capillary tubes

Dropper bottle

Paper clips

Three watch glasses

Stopwatch

Graph paper

Colored pencils

Deionized water

Isopropanol

Ethanol

Soap solution

Sugar

Solid NaCl

Gt Chemistry

Unit: Chemical Bonding

PROCEDURE

PART I. Density of States.

1. Observe the demonstration of water in its three states. Note: 20.0 mL samples of liquid water were used to make the ice and steam.

2. Density is the measure of mass per unit volume. Since liquid water has a density of 1.0 g/mL, the 20.0 mL samples used will each have a mass of 20.0 g. Record your observations and rank the states from highest density to lowest density in the data table.

DATA TABLE 1: Density of States

State

Observations

Solid (Ice)
Liquid (Water)
Gas (Steam)

PART II. Capillary Action.

1. Take a capillary tube and place it in the isopropanol. Record your observations of what happens in the data table.

2. Take a second capillary tube and place it in the water. Record your observations of what happens in the data table.

DATA TABLE 2: Capillary Action

State

Observations

Isopropanol
Water

PART III. Surface Tension.

1. In the beaker of 25 mL isopropanol, try to float a paper clip on the surface. Record your methods and results in the data table.

2. In the beaker of 25 mL water, try to float a paper clip on the surface. Record your methods and results in the data table.

3. After your final attempt in Step 2, add a drop of soap solution to the water. Record your observations of what happens in the data table.

DATA TABLE 3: Surface Tension

State

Observations of Paper Clip Floating Attempts

Isopropanol
Water
Water + soap

PART IV. Universal Solvent.

1. On a watch glass, place two small samples of sugar. On separate watch glasses, do the same for NaCl and vegetable oil.

2. For each watch glass, place a few drops of water on one sample. Place a few drops of cyclo-hexane on the second sample.

3. Record your observations of the dissolving capabilities of each solvent in the data table.

DATA TABLE 4: Universal Solvent

Solvent

Solute

/ Water / Hexane
Sugar
NaCl
Oil

PART V. Heat Capacity.

1. Have one group member prepare to start the stopwatch.

2. Simultaneously, place one drop each of water, ethanol, and isopropanol on the lab table and start the stopwatch.

3. Record the time it takes for each drop to evaporate.

DATA TABLE 5: Heat Capacity

Time to Evaporate (s)

Water / Ethanol / Isopropanol

PART VI. Hydrogen Bonding.

1. Complete the data table based on each of the compounds provided. Identify whether each compound is ionic or covalent, polar or nonpolar, and whether a dipole in the compound would be permanent or induced. Finally, list the total number of electrons in each compound.

2. Using a different color for each group of compounds, plot the boiling points on the y-axis and the total number of electrons on the x-axis. Connect the points for each group of compounds.

DATA TABLE 6: Hydrogen Bonding
Compound / Ionic or Covalent / Polar or Nonpolar / Dipole: Permanent or Induced / Total Number of Electrons in Compound / Boiling Point (°C)
CH4 / -164
SiH4 / -111.8
GeH4 / -88.5
SnH4 / -52
NH3 / -33
PH3 / -87.7
AsH3 / -55
SbH3 / -17.1
H2O / 100
H2S / -60.7
H2Se / -41.5
H2Te / -2.2
HF / 20
HCl / -85
HBr / -67
HI / -35

ANALYSIS

1. Based on your observations, which state of water is the most dense? How could intermolecular forces explain this result?

2. Which compound(s) exhibited capillary action? What intermolecular forces would be present to allow for capillary action?

3. Did the paper clip float in either liquid? If so, which?

4. What effect did the soap solution have? Why do you think this happened?

5. Which solvent would you consider “universal”? Why? Is this title appropriate?

6. Which compound evaporated fastest? Which compound evaporated slowest? Use intermolecular forces to explain your observations.

7. Describe any trends on the boiling point graph.

8. Based on your boiling point graph, which elements are capable of hydrogen bonding? What do they have in common? Why would this matter?