any characteristic of a material that you can observe without change the identity of a substance that make the material is a

Any characteristic of a material that you can observe without changing the identity of the substances that make up the material is a physical property. Examples of physical properties are color, shape, size, density, melting point, and boiling point.

Explanation:

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds

sex cells are usually half's then they find another half and make a fertilize egg