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With mouth wide open, vibrating air coming up the throat from the vocal chords leaving the open mouth and spreading in all directions. Hi, I am Janice VanCleave, author of 50+ best-selling science experiment books for children ages 4 through high school. I taught science for 27 years and now am creating this science website.   My scream was not staged. The picture was to be of two adult cats, which I was holding. A microsecond before the camera snapped, the two cats dug their claws into my skin as they prepared to leap out of my arms. A picture like this is great for making inferences. Kids could make "guesses" as to why I am screaming. They would be drawing on facts from the photo, such as I look like I am in pain or maybe I am just pretending.

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Home » Types of Crystals

Types of Crystals

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CRYSTALS are solids with particles arranged in a regular, repeating pattern with flat surfaces.

Most solids are CRYSTALLINE SOLIDS, which are solids made of crystals. For example, when liquid water freezes, the water molecules link together forming ice crystals. A large piece of ice is made up of many small ice crystals that fit together like a puzzle. The shape of crystals depends on the arrangements of the particles within it.

A UNIT CELL is the smallest group of particles within a crystal that retains the geometric shape of the crystal. For example, the unit cell of a table salt crystal is cubic. For salt crystals to form, the cubic cells must be able to move about so that they can be positioned with their faces (flat surfaces) against one another.

Precipitates

PRECIPITATES are crystals that form when the solute (dissolved part) of a solution (mixture of a solute + a solute) precipitates. PRECIPITATION means that some of the solute falls out of the solution. Precipitation occurs when there is more solute than can dissolve in the solvent.

Different things can cause precipitation including, agitation and evaporation.

Evaporites

As the water evaporates from an aqueous (water) salt solution, the solution becomes more concentrated with salt; that is, as the amount of water decreases, there is more salt mixed with a smaller amount of water. Then there is more salt than can dissolve in the remaining water, the salt precipitates. As the salt (solute) precipitates its particles bond (link) together, forming unit cells that comprise a crystal. The more unit cells that bond together, the larger the crystal. Crystals that form due to evaporation, are called EVAPORITES.