Question

practice it!
select the list of examples that are chemical changes.
chewing food, food rotting, chopping wood, crumpling paper
digesting food, fireworks exploding, balloon popping, cutting hair
cutting hair, blowing up a balloon, boiling water, melting ice
wood burning, fireworks exploding, food rotting, pipes rusting
remember:
a chemical change occurs when the matter changes into something new. look for light,
heat, bubbles, or new substances.

Explanation:

• First option: Chewing food (physical - just breaking into smaller pieces), chopping wood (physical - size change), crumpling paper (physical - shape change). Food rotting is chemical (new substances formed due to decomposition). But since most are physical, this option is wrong.
• Second option: Balloon popping (physical - pressure change), cutting hair (physical - size change). Digesting food (chemical - enzymes break down food into new substances), fireworks exploding (chemical - new substances like gases formed). But with non - chemical changes, this option is wrong.
• Third option: All are physical changes. Cutting hair (size), blowing up a balloon (shape, pressure), boiling water (state change - liquid to gas, no new substance), melting ice (state change - solid to liquid, no new substance).
• Fourth option: Wood burning (chemical - forms ash, gases like \(CO_2\)), fireworks exploding (chemical - new substances), food rotting (chemical - decomposition), pipes rusting (chemical - iron reacts with oxygen and moisture to form rust (\(Fe_2O_3\cdot xH_2O\))). All are chemical changes.

Answer:

wood burning, fireworks exploding, food rotting, pipes rusting (the fourth option)