These beautiful man-made crystals float to the top of a super-cooled bismuth melt and form within minutes. Bismuth is one of the few materials that have a greater density as a liquid than as a solid. Only a few other materials such as water, gallium, and germanium exhibit this property. The trigonal crystal structure accounts for the cubic formations. The iridescent rainbows of colors observed are caused by light scattering off thin layers of bismuth oxide formed when the surface of the hot bismuth reacts with the air. Specimens range from 12 to 17 g with a density of 9.81 g/cc. Great for teaching about crystals, states of matter, or even as a gift!
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Bismuth is a very unusual and rare metal that is solid at room temperature. It is more rare than platinum, ranking number 69 out of the 75 listed rare elements found on Earth's crust. One very interesting thing about bismuth is that its liquid form is denser than its solid form. So as bismuth crystallizes, its solid form floats above the liquid. This effect is only found in 3 other cases (water, gallium, and germanium).
Bismuth crystals are man-made or man 'grown'. Their growing time is between 5-10 minutes after forming in a supercooled bismuth melt. In its solid form, bismuth is incredibly fragile. However, the crystals form to show perfect cleavage, making it tempting to handle and touch. The reason the crystal structure is so fragile is because the rapid growth causes hollow forms, called 'hopper crystals'.
The iridescent coloring is due to a thin layer of bismuth oxide that forms on the surface of the crystal as it cools. This is actually interference coloring, similar to the coloring you see on soap bubbles and on oil slicks, and is based on how thick the oxide grows. The brightness and color intensity can vary from sample to sample, depending on the quality and purity of the bismuth used.
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Jan 6, 2017 | By Jeanine of Portland, ON United States
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Sep 13, 2013 | By P. Kawalec of Ann Arbor, MI United States
Bismuth Crystal, very cool!
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This product will support your students' understanding of the Next Generation Science Standards (NGSS)*, as shown in the table below.
Suggested Science Idea(s)
Students can use Bismuth Crystals to plan and conduct an investigation to describe and classify different kinds of materials by their observable properties.
Students can use Bismuth Crystals to make observations and measurements to identify materials based on their properties.
Using Bismuth Crystals, students can develop models to describe the atomic composition of simple molecules and their structures or properties.
Students can investigate Bismuth Crystals in an investigation to describe that synthetic materials come from natural resources and can have an impact on society.
Using Bismuth Crystals, students can construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the Periodic Table, and knowledge of the patterns of chemical properties.
These beautiful, man-made Bismuth Crystals are cubic and iridescent. Students can use them to plan and conduct an investigation to describe and classify different kinds of materials by their observable properties.
DCI-HS/PS1.A: Structure and Properties of Matter.
The Periodic Table orders elements horizontally by the number of protons in the atom's nucleus and places those with similar chemical properties in columns. The repeating patterns of this table reflect patterns of outer electron states.
* NGSS is a registered trademark of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of, and do not endorse, this product.