Question

what do these two changes have in common?
rust forming on a metal gate
saliva breaking down a piece of bread
select all that apply.
both are chemical changes.
both are changes of state.
both are caused by cooling.
both are only physical changes.

Explanation:

Rust formation is a chemical reaction where metal reacts with oxygen and water to form a new substance (rust). Saliva breaking down bread involves enzymes in saliva causing a chemical change in the bread's carbohydrates. Both create new substances, so they are chemical changes. They are not changes of state, caused by cooling, or physical changes.

Answer:

• Both are chemical changes.