Molecular Motion of Matter and the Effect of Lemon in Reducing the Smell of a Fish (page 2)

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Author: Janice VanCleave

Try New Approaches

Does temperature affect the diffusion of the amine vapor? Repeat the experiment two times, first setting the cups in bowls of ice water, and then placing them in bowls of hot water.

Design Your Own Experiment

    1. Demonstrate the fact that water molecules are in constant motion. Mix together in a 1-quart (1-liter) jar, 1 teaspoon (5 ml) of sodium chloride (table salt), five drops of green food coloring, and 1 cup (250 ml) of water. Tilt the jar and slowly pour a second cup (250 ml) of water down the inside of the jar. The result is a layer of green water covered by a layer of clear water (see Figure 22.2). Place the jar where it can remain undisturbed for three days. Observe the contents of the jar as often as possible. The motion of the water molecules is evident as the two layers start to mix. The end result is a uniformly green-colored liquid.
    2. Determine whether temperature affects the molecular motion of the water molecules. Repeat the previous experiment two times, first using chilled water with ice cubes and placing the jar in a refrigerator, and then using hot tap water and placing the jar in a warm area.
  2. Molecules rotate about their axes, as does the earth. The rotational energy creating this molecular motion can produce heat. For example, in microwave heating, water in food absorbs the energy waves, or microwaves, causing the individual water molecules to spin like tops. As these molecules twirl, they hit and rub against other water molecules. Rubbing your hands together very quickly demonstrates the ability of friction to produce heat. Predict the effect of microwaves on materials that do not contain water, such as a paper plate. Would the paper get hot? Why?
  3. The three phases of matter—solid, liquid, and gas—have distinct physical properties because of the differences in their molecular motion. The amount of energy that a substance possesses determines its molecular motion and thus its phase of matter. Molecular motion is directly dependent on energy. As molecular motion decreases, molecules get closer together and the cohesion (attraction between like molecules) increases. Solids have the lowest energy, the least molecular motion, and the greatest cohesion between molecules. Demonstrate the physical changes made by increasing molecular motion by heating ice. You could display diagrams to illustrate the closeness of the molecules in different phases.
  4. Gases and liquids are classified as fluids because both are able to flow and to change their shapes. Sir Isaac Newton (1642–1727) is credited with stating the relationship between temperature and the viscosity of fluids. This law of viscosity states that only a change in temperature affects the viscosity of a fluid. Newton had never seen the "Glob," a creepy ooze that, like other fluids, has an increase in molecular motion with an increase in temperature but that, unlike other fluids, has its viscosity increase with an increase in pressure. Pressure makes it behave as a solid. Since the Glob defies Newton's law about fluids, it is considered a "non-Newtonian" fluid.
  5. Molecular Motion: A Matter of Energy

  1. Make the Glob by using the following instructions. CAUTION: Keep the Glob out of reach of small children. It is not edible.
    • Combine 4 ounces (120 ml) of Elmer's® school glue, 4 ounces (120 ml) of distilled water, and ten drops of green food coloring. Stir well and set aside.
    • In a separate bowl, combine 1 teaspoon (5 ml) of sodium borax with 1 cup (250 ml) of distilled water. Stir well.
    • Pour both solutions into an empty bowl simultaneously.
    • Stir and dip the thick Glob out of the bowl.
    • Knead the Glob with your hands until it is smooth and dry.
  2. Try the following experiments with the Glob.
    • Roll it into a ball and bounce it on a smooth surface.
    • Hold it in your hands and quickly pull the ends in opposite directions.
    • Hold it in your hands and slowly pull the ends in opposite directions.
    • Place a lemon-size piece into a microwave dish and heat for one half minute in a microwave oven. Note: Microwave heating will make the Glob too hot to handle. Allow it to stand in the oven for about five minutes so that it returns to room temperature.
    • Place a piece in a freezer overnight and then allow it to return to room temperature.

Note:The Glob will keep for weeks in a plastic bag, but after much handling it will dry out.

Get the Facts

  1. The continuous movement of molecular particles is called Brownian movement. Find out more about the perpetual dancing of molecules and the experiment that led Robert Brown, a Scottish scientist, to discover their motion.
  2. The smell of the sea is due to the release of amines by decaying marine life. Because these amines are associated with the decaying flesh of animals, the common names of two amines are cadaverine (from "cadaver") and putrescine (from "putrefy"). An amine is considered a base as defined by the Bronsted-Lowry theory and by the Lewis theory. Use a chemistry text to find out more about this organic base. What is its general chemical structure? What is its distinguishing chemical makeup? How are amines related to ammonia? Include in your findings the reaction between an amine and an acid.
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