Question

When elements combine to form compounds:

-their properties do not change.
-their properties are completely random.
-their properties change completely.
-their properties are an average of all elements in the compound.
-none of the above

Answer 1

When elements combine to form compounds, their properties change completely, resulting in a substance with unique chemical and physical characteristics different from those of its constituent elements, as exemplified by water formed from hydrogen and oxygen.

Step-by-step explanation:

When elements combine to form compounds, their properties change completely. A compound consists of atoms of two or more different elements combined in a small, whole-number ratio, and these atoms can separate and recombine to give new substances. However, through this process, the atoms are neither created nor destroyed. Contrary to being an average or remaining unchanged, the resultant compound exhibits new chemical and physical properties that differ significantly from those of its constituent elements.

For example, hydrogen and oxygen are both gases at room temperature, but when they combine to form water (H2O), the resulting compound is a liquid with properties vastly different from either hydrogen or oxygen. This illustrates how the formation of compounds is a transformational process, leading to materials with unique characteristics.