Question

You forgot to dry the bread knife when you washed it and reddish brown spots appeared on it .what type of change is this.explain

Answer 1

Answer:

Chemical change.

Explanation:

Reddish brown spots are Rust particles. Iron part of the knife has chemically combined with moisture (since it was not dried) and atmospheric oxygen to form Rust and Water molecules. Rust is identified by its characteristic reddish brown colour.

Answer 2

The appearance of reddish-brown spots is a chemical change.

• The bread knife reacted with moisture thus forming reddish-brown spots. This change is indicative of rusting of the knife.
• The presence of moisture causes rusting of iron.
• The chemical reaction of iron and moisture is -
• 4Fe + 3O2 + 2H2O --> 2Fe2O3.H2O.
• In the mentioned chemical reaction, Fe refers to iron, O2 refers to oxygen, H2O refers to water and Fe2O3.H2O refers to rust.