Grow Alum Crystals
Hosted by: UT Austin Texas Materials Institute
Visit our Booth: Saturday, February 27, 2021, 12 p.m. - 4 p.m.
Recommended Grades: 5th, 6th, 7th
Some background: What are crystals?
Crystals are a special type of solid materials where the atoms or constituents are arranged in a repeated pattern. This pattern causes the materials to make all sorts of shapes such as triangles, rectangles, and squares. The way the atoms organize will dictate the mechanical and electrical properties of the materials. Diamonds are an example of crystals that appear in nature and are formed when liquid rock or magma cools down. However, diamonds can be also grown in a laboratory, and in that case, they are called synthetic diamonds. Diamond is the hardest material on earth and it is formed out of carbon atoms. Interestingly, not all materials formed out of carbon are diamonds. For instance, the tip of a pencil is also formed out of carbon, but in this case, the carbon atoms are organized in sheets and the material is soft. Another example of natural crystals is quartz which is formed out of silicon and oxygen. The sand grains are composed of quartz.
Besides from the melt, another way crystals are formed is from solution as the liquid evaporates or cools down. This is the easiest way to grow crystals. For example, kitchen salt crystals are formed from salty water.
Many synthetic crystals have very important applications. For instance, silicon crystals that are grown using sand are used in computer chips as well as in solar cells.
- Learn how to grow crystals starting from solutions
- Learn how to make solutions
- Identify parameters that govern the crystal growth
- distilled water
- measuring cup
- a pan for boiling the water
- alum (found at the grocery store in the spices aisle)
- kitchen scale
- few glass containers
- few shallow saucers
- filter paper
- food coloring (optional)
- nylon string and cardboard
How does this activity connect to STEM and today's GirlDay Theme of Designing for Communities and Designing fun? Engineers and scientists design new materials and products that improve wellness for communities. Developing procedures for growing crystals of different materials had a deep impact in many industries as well as in medicine. For instance, solving the structure of the spike protein in the novel coronavirus paved the way for developing the Moderna and Pfizer vaccines. The crystals were grown and the structure was solved here at UT Austin by Dr. Josh McLellan.
Activity Video & Resources
Check out the video below for detailed instructions and a demonstration with Raluca, an engineer with the Texas Materials Institute at UT Austin.
Find the detailed instructions on how to grow alum crystals in the PDF below so you can follow along.
The Texas Materials Institute (TMI) at the University of Texas at Austin was established in 1998 to ensure that UT-Austin achieves excellence in graduate education and research in the broad field of materials. The role of TMI is to be a “virtual” department that guides the destiny of materials science and engineering on the UT campus without imposing the limitations or boundaries inherent to departmental structures. TMI provides faculty and students on the UT-Austin campus with the instrumentation and associated infrastructure needed to conduct modern materials research. In addition, TMI houses the Materials Science and Engineering Graduate Program and Undergraduate Minor. The MS&E Graduate Program consistently is highly ranked by the U.S. News and World Report.
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