Chemical properties of free alkali metals do not lend themselves to hands-on activities for high school laboratories due to the hazardous nature of these elements. With great care, you can carry out lecture demonstrations with selected alkali metals. Several demonstrations are detailed in the next section. Activities involving alkali metal compounds do exist and are available in many laboratory manuals. Some chemistry of these metals is also covered in the demonstration section of this module.

Alternatively, audio-visual aids such as the CHEM Study film, Chemical Families; the Project Seraphim Periodic Table Videodisc; available video lecture demonstration tapes published as companions to new college general chemistry texts; or the "Doing Chemistry" videodisc program can serve as excellent substitutes for the hazardous live activities

Demonstration CAUTION: Use appropriate safety guidelines in performing demonstrations.

Demonstration 1: Identification of Metal Ions by Flame Tests
Materials
Some of the following ionic solids:
Barium chloride, barium hydroxide*, barium nitrate
Calcium carbonate, calcium chloride*, calcium nitrate*
Cesium carbonate*, cesium chloride*, cesium nitrate
Copper(II) acetate*, copper(II) chloride*, copper(II) sulfate
Lithium carbonate, lithium chloride*, lithium nitrate
Potassium nitrate, potassium carbonate, potassium chloride*
Rubidium carbonate*, rubidium chloride, rubidium hydroxide*
Sodium chloride, sodium nitrate*
Strontium chloride*, strontium nitrate*
*Somewhat soluble in 95% ethanol (see Procedure B)
Striker or matches
Burner
Safety goggles
Small glass bottles with screw caps for ionic solids above
Pump hair spray bottles
Petri dishes
Ethanol or methanol
Safety
Try all demonstrations ahead of time to ascertain the safest reaction conditions. Be
aware that any of these methods allows metal compounds to be released into the air.
Use adequate ventilation. Always wear safety goggles for chemical demonstrations.


Procedure A: Several Powdered Solids
Select several metallic salts from the preceding list. Powder each by crushing a one-tablespoon
sample in a clean mortar and pestle. Place each powder in a separate labeled, tightly capped bottle
(100-mL or larger). Set up a burner, making sure the flame is the normal light blue. Vigorously
shake each bottle one at a time to create a finely divided solid mist, and remove the cap
while holding the mouth of the bottle upright and close to the burner's air intake. A prolonged colored
flame will be observed. If the procedure is carried out in a darkened room and students are
provided with inexpensive plastic diffraction gratings (available as 2" x 2" mounted
slides from Edmund Scientific, Great Barrington, NJ 08007), they may be able to observe the line
spectra of the metals.
Procedure B: Ethanol (or Methanol) Solutions
The solids in the preceding list that are marked with asterisks (*) are
somewhat soluble in ethanol (or methanol) and are good choices for use in this procedure. Place a
pea-sized quantity of several of these powdered solids in glass Petri dishes or small beakers.
Cover the solid with a thin layer of ethanol or methanol. Darken the room if possible and ignite
the alcohol with a long match or taper. The colors will continue as long as there is alcohol to burn.
Procedure C: Aqueous Solutions
Use pump spray bottles, obtainable in garden shops. Fill each bottle with dilute (0.1 to 0.5 M)
solutions of selected compounds listed above. (You probably have some of these solutions already
prepared on your shelves.) Spray the liquids into the burner flame, one at a time.
Observe instant, bright bursts of color.
Discussion
The colors of the flames will be as follows:
Demonstration 2: Reactions of Metals with Water
You should perform these activities as a demonstration rather than as a student activity because
of the high reaction rates, the somewhat variable way in which the reactions occur, and
the dangers involved in handling sodium. Because of the danger of storing and handling
to extend
Purpose
To demonstrate activity level of alkali and alkaline earth metals in the presence of water.
Materials
Lithium metal, small piece
Sodium metal*, small piece
Potassium metal, small piece
Calcium metal, small piece
Magnesium ribbon, 6-10 cm
Water
Liquid detergent (not basic), few drops
Phenolphthalein solution (0.01 g phenolphthalein per 100 mL ethanol)
Beaker
4 Glass Petri dishes or crystallizing dishes
Fine mesh wire gauze
Test-tube and stopper
Funnel (glass)
Overhead projector
*Dri-Na works well here in place of sodium metal. Dri-Na is sold by Flinn
Chemical Company. It is an alloy containing 12% sodium with lead. This
alloy generates hydrogen gas slowly and safely.
Safety
Sodium and potassium are potentially explosive if large chunks are used, or if
a peroxide coating exists on the surface of the metal. Use only freshly cut pieces
of shiny metal. You might consider using Dri-Na in place of the sodium metal.
  1. Procedure
Part 1
  1. 1. Fill a glass vessel (Petri dish or beaker) half-full with water. Add three drops of phenolphthalein and three drops of neutral detergent. (Place the Petri dish on overhead projector.)
  2. 2. Drop in a small piece of lithium and place the wire gauze over the top of the glass container (or if using the overhead, use the cover of the Petri dish).
  3. 3. Repeat Steps 1-2 with sodium, potassium and calcium. Note that calcium oxidizes easily and reacts vigorously with water. Purchase only small quantities of calcium and keep tightly covered when not in use. If your calcium is white and powdery, it has oxidized. Choose only metallic pieces of calcium for the above test.
Discussion
The equations for the reaction are:
The trail of zigzagging sodium (potassium, calcium) should leave a pink trail as the indicator reacts with the metal hydroxide formed.

Part 2

1. Fill a test-tube completely with water. Place a 6-10 cm coil of magnesium ribbon into the test-tube mouth. Stopper the test-tube, invert it into the tall narrow beaker, which has been half-filled with water, and remove the stopper. Heat the water. Have students observe and record results. or

2. Place a 6-10 cm coil of clean magnesium ribbon in a beaker half-filled with water. Invert a short stem glass funnel over the magnesium and place a test-tube over the funnel stem. Have students observe and record results. Next, heat the water to near boiling and have students record observations.Next, heat the water to near boiling and have students record observations.

Discussion

Once again, magnesium readily forms oxide coating on its surface. The pieces of magnesium used for the demonstration should be cleaned beforehand by dipping all pieces in 1-3 M HCl for a short time and then rinsing with tap water and drying.

The equation for the reaction is:

NOTE: This reaction happens very slowly, if at all, at room temperature, but bubbles of hydrogen are observed at elevated temperatures.

Compare and contrast the reactivity of the four metals with water. Have students explain the differences in terms of chemical periodicity.

[The revised ChemStudy film "Chemical Families", now available on videotape, beautifully demonstrates the reactivity of alkali metals with water and halogens. Many college texts now make available to teachers videotaped demonstrations that include reactions of alkali metals.]

Demonstration 3: Solvay Process Demonstration for the Commercial Preparation of NaHCO3 and Na2CO3

Materials

Safety

  1. Always try demonstrations before doing them for a class. Wear safety goggles when doing any chemical demonstration. Concentrated ammonia is an eye, nose, and throat irritant. Be sure you have adequate ventilation. Dry ice is extremely cold and can cause burns. Handle with care. Use gloves.

Directions

1. Prepare a warm water bath by heating ~600 mL water in an 800-mL beaker to 50-60 °C.

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