Question

When hydrogen burns in air, the change is chemical. Select two reasons to support this assertion.

• A. It forms water and molecules are changed.
• B. It forms water and molecules are not changed.
• C. New products are formed.
• D. Changes are reversible.

Answer 1

Answer: (A), (C)

The correct options are
A It forms water and molecules are changed.
C New products are formed.

A chemical change is a permanent, not easily reversible change in which the identity of the substance is altered to produce one or more new substances.
Reaction:
$H_2+O_2\to H_{2}O$
as here new compound forms so its a chemical change.