TITLE:
Design Expert Software Being Used to Explore the Factors Affecting the “Water Garden”
AUTHORS:
Zelin Miu, Yichen Lu
KEYWORDS:
Univariate Experiments, Experimental Teaching, Experimental Design
JOURNAL NAME:
American Journal of Analytical Chemistry,
Vol.16 No.6,
June
30,
2025
ABSTRACT: The chemical garden experiment demonstrates the formation of plant-like crystal structures using metal salts and sodium silicate. This visually appealing experiment is ideal for chemistry education. In the experiment, metal salt crystals react with sodium silicate, forming membrane structures through osmotic pressure and hydrostatic forces, promoting the growth of silicate structures. Different metal salts produce varied colors and shapes, enhancing the educational value. A study using Design Expert software explored the relationship between metal salt solubility and crystal growth height. Experiments with salts like copper (II) nitrate and iron (III) nitrate showed a linear correlation between solubility and growth height. Higher solubility salts led to taller structures due to sufficient ion supply. The linear regression model confirmed this correlation, with significant statistical results. This study highlights the role of solubility in crystal growth, providing valuable insights for educational purposes. Future research could explore variables like temperature and sodium silicate concentration to deepen understanding of the chemical garden phenomenon. The experiment’s basic principle involves the reaction of metal salt crystals with sodium silicate solution, releasing metal ions and forming an insoluble metal silicate membrane. Water molecules enter the membrane through osmotic pressure, increasing the internal liquid volume, causing hydrostatic pressure changes, and promoting the formation and growth of new membranes. The color and surface shape of the metal salts depend on the type of salt used, such as copper salts producing blue, iron salts producing reddish-brown, and cobalt salts producing purple or red structures. The study used nine metal salts, including copper (II) nitrate, iron (III) nitrate, and cobalt (II) nitrate. Each salt has a different solubility, and the experiment measured the crystal growth height. Data analysis showed that higher solubility salts generated taller silicate structures. These findings align with theoretical expectations, where higher solubility salts facilitate rapid membrane formation and upward growth of silicate structures. In summary, the research successfully demonstrated the use of Design Expert software to quantitatively analyze the significant impact of metal salt solubility on crystal growth characteristics. This not only deepens the understanding of the process but also offers practical advice for teachers to reveal the underlying physics in classroom or laboratory activities.