Question

A chemist mixes oxygen gas and hydrogen gas to form water, which is composed of one oxygen and two hydrogen atoms per molecule. What has occurred? A physical change B chemical change C combustion D precipitation

Answer 1

B chemical change i think

Answer 2

Answer: The formation of water is a chemical change.

Explanation:

Physical change is defined as the change in which change in shape and size takes place. The chemical composition of a substance remains the same. No new substance is formed during this.

For Example: Melting of ice

Chemical change is defined as the change in which change in chemical composition takes place. A new substance is formed in this.

For Example: Formation of water molecule.

The chemical equation for the formation of water molecule follows:

$2H_2+O_2\righatarrow 2H_2O$

Hence, the formation of water is a chemical change.