Practice!

Sample Problem

Which of the following can be considered an example of a physical change?

Boiling water to form steam

Rust appearing on an iron surface

Folding a paper airplane

Burning fuel to power an engine

Formation of a canyon from water erosion

Solution

Phase changes (melting/freezing and boiling) are considered physical changes. Rust and combustion are chemical changes since new products are formed from a reaction (iron oxide, carbon dioxide and water).