Question

a student reads the following four unrelated observations in her science journal.
observation 1 \the cooked egg looks very different from the uncooked egg.\
observation 2 \the indicator changed colour when added to the solution.\
observation 3 \the wet steel wool turned a reddish colour when exposed to air.\
observation 4 \the salt dissolved quickly when it was stirred in the solution.\
which of the observations listed above identifies a reaction in which oxidation has taken place?
a. observation 1
b. observation 2
c. observation 3
d. observation 4

Explanation:

Oxidation is a chemical reaction where a substance reacts with oxygen. In Observation 3, wet steel wool (which contains iron) reacts with oxygen in the air to form iron oxide (rust), which is reddish - brown. Observation 1 is a physical change (cooking an egg is a denaturation of proteins, a physical change at the molecular level in terms of structure but not a chemical reaction with oxygen). Observation 2 is likely a pH - related color change (not oxidation). Observation 4 is a physical change (dissolving of salt).

Answer:

C. Observation 3