A crystal is a special type of solid where the particles are arranged in an orderly and repeating pattern. When solids are dissolved in water, they form a solution, like when salt and water mix. As particles dissolve in water, the particles of the solid separate and distribute evenly throughout the mixture. Sometimes two dissolved particles move closer to each other and begin to attract, causing them to stick together. Over time more and more particles attach to the growing solid and “drop out of the solution”. The solid formed is a special compound called a crystal.
In this activity students will explore how crystals are made.
Measuring cups (1/2 cup)
Alum (spice can be found at grocery store)
- Add ½ cup of hot water to 2 ½ tablespoons of alum.
- Crystals will form within 30 minutes.
- Want bigger crystals add more alum to the water.
How It Works:
When the alum and water mix, the alum begins to accumulate in clusters and as the warm water evaporates, it leaves the lumped crystals behind. The alum forms not just a solid, but a solid with a repeating pattern, making a crystal.
Discussion Questions to Ask:
- How did were the crystals made?
- What characteristics do the crystals have?
There are many places where crystals grow in nature, like ice crystals are often formed in the winter, in colder climates as the liquid molecules freeze. Also in caverns, there are stalagmites and stalactites that are crystals of calcium carbonate. When teaching concepts like crystals, young students may become bored as the formation of the crystal may take longer than one class period. To keep the students’ attention, incorporate crystals-related activities in other areas, i.e. math (counting or matching crystals), art, geography (where do crystals form in nature), even in physical education (students can pretend to be frozen crystals and play tag). It is best to start this activity and others that take more than one day on a Friday, that way when the students return on Monday the process is complete. For other science teaching tips related to crystals, visit: http://bit.ly/10l3FXy
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