Is glass the result of a physical or chemical change?

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The process of making glass involves a chemical change. While a physical change describes change in the superficial properties of a substance-- like melting ice into water, or tearing up a piece of paper-- a chemical change alters the chemical makeup of the substance itself. 

Glass is made when sand is heated to a very high temperature, causing it to melt. The main component of sand is silicon dioxide, and when this is heated at extreme temperatures, the chemical structure of the silicon dioxide begins to rearrange! Actually, because of its unique molecular structure, we sometimes refer to glass as an "amorphous solid." This means that it behaves like a solid, but the molecular structure isn't the typical crystalline pattern we find in other solids. Different substances may be added to sand before melting or to the molten glass to change the molecular structure or final color of the resulting glass.

Glass can undergo physical changes, too! Have you ever seen glass shatter? This is an example of a physical change. Even though the initial drinking glass or window broke into lots of pieces, the chemical structure is essentially still the same.

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