Science PSSA Practice Test

A substance made up of atoms of two or more different elements joined by chemical bonds is referred to as a compound. Compounds are formed through the process of chemical reactions where elements combine in specific ratios, creating a substance with properties that are distinct from those of its individual elements.

For instance, water is a compound formed from hydrogen and oxygen atoms bonded together. The characteristics of water differ from those of hydrogen (a gas) and oxygen (also a gas) when they exist separately. This illustrates how the chemical bonding in compounds leads to new physical and chemical properties.

In contrast, a mixture involves two or more substances that are not chemically bonded and can be separated by physical means, while an element consists of only one type of atom and cannot be broken down into simpler substances. A solution is a specific type of mixture where one substance is dissolved in another, but the components retain their individual properties and do not form new chemical bonds.