Question

An example of a chemical change is

A) burning wood.
B) breaking a glass.
C) folding paper into a frog.
D) molding clay into a snake.

Answer 1

Burning wood. At the beginning, the wood is left untouched. When lit it burns, causing it to have a different effect.

Answer 2

A chemical change changes the chemical identity of a substance, whereas a physical change does not.

Combustion takes a hydrocarbon and produces water and carbon dioxide. Breaking glass takes one piece of glass and makes it smaller. Folding paper changes its shape, as does molding clay.

In general, if there is evolution of gas, formation of a precipitate, or a color change, a reaction has usually occurred. The answer is A.