Alkali Metals & Ionization

Purpose

To demonstrate that reactivity increases as valence electrons become easier to remove in alkali metals.

Procedure

1. Preparation:

• Gather materials: Petri dish, water, phenolphthalein, freshly cut alkali metal samples (lithium, sodium, potassium), stick lighter, hexanes, and 3 L conical flasks.

1. Setting Up the Experiment:

• Fill the Petri dish with water and add a few drops of phenolphthalein.

1. Adding Lithium:

• Take a freshly cut half lentil-sized sample of lithium and add it to the dish.
• Observe the fizzing and movement of lithium in the water.

1. Adding Sodium:

• Repeat the process with sodium, observing the reaction.

1. Adding Potassium:

• Carefully add potassium to the dish. Note that potassium may catch fire upon reaction.

1. Igniting Hydrogen:

• The hydrogen gas produced by the reactions of sodium and lithium can be ignited using a stick lighter, resulting in colored flames.

1. Preparation of Metals:

• Rinse the alkali metals with hexanes to remove any mineral oil.
• Use a paper towel to absorb excess oil from the metals before adding them to the water.

1. Safety Considerations:

• Be cautious with the size of the metal pieces.
• If using larger samples, consider conducting the experiment in a beaker with a cover.
• Watch for smoke if any mineral oil is not completely removed.

1. Using Conical Flasks:

• Use 3 L conical flasks to trap hydrogen gas.
• Invert a paper cup on the flask to trap the hydrogen gas, which can ignite.

Safety Precautions

• Only bring small amounts of alkali metals to the experiment.
• Handle all materials with care to prevent accidents, especially with potassium.
• Ensure proper ventilation when conducting the experiment.