Fallacy of Composition

Arbitrarily attributing to something the property of its constituent parts.
Believing that the properties of the parts are automatically transferred to the whole.

General form:
"A is made of Bs, and all Bs are C, therefore A is also C."

Typical example:
"The bricks that make this house are cubic, therefore the house must be cubical."

There is no logic rule that states that the property of an element is automatically transferred to a collection of such elements.