It can be challenging to find a safe wet lab activity that demonstrates the periodicity of common periodic properties. In this International Year of the Periodic Table, try incorporating a conductivity probe, such as our versatile Go Direct Conductivity Probe, to help students visualize data.
For the experiment, students follow this simple procedure:
- Place 5 mL of distilled water in four test tubes in a test tube rack.
- Add 10 drops of 0.1 M solutions of Mg(NO3)2, Ca(NO3)2, Sr(NO3)2, and Ba(NO3)2 to each test tube.
- Add 10 drops of 0.1 M K2SO4 to each test tube and observe the reactions.
- Use a conductivity probe to measure the conductivity of the liquid in each test tube. Important: Carefully rinse the sensor with distilled water between test tubes.
After collecting data, have students discuss the relationship of the amount of precipitate they observe in each test tube after the reaction, the conductivity of the solution, and the position of each alkaline earth metal on the periodic table. You can use the following questions as discussion prompts:
- What is the relative reactivity of the alkaline earth metal nitrates?
- Why did you use nitrate salts of the alkaline earth metals instead of the pure elements?
- How would you expect the alkaline earth metal elements to react with water?
- How would you expect the alkali metals to react with water?
- Would this same experiment work with the nitrate salts of the alkali metals?
A nice extension is to ask your students if there are other salts besides K2SO4 that would produce similar results when reacted with the ions of the alkaline earth metals.
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