General Biology Study Notes: Matter, Elements, and Compounds

Bio Notes 2.1: Matter, Elements, and Compounds

Introduction to Matter

All living and non-living things are composed of matter. Understanding the nature of matter is fundamental to biology, as it forms the basis of all biological structures and processes.

• Matter is defined as anything that occupies space and has mass.

• Matter exists in three primary states: liquid, gas, and solid.

• Examples: Water (liquid), oxygen (gas), and ice (solid).

Elements

An element is a pure substance that cannot be broken down into simpler substances by chemical means. Elements are the building blocks of matter.

• Element: A substance consisting of atoms with the same number of protons.

• Each element has unique properties and is represented by a chemical symbol (e.g., H for hydrogen, O for oxygen).

• Humans require 25 elements for life, while plants need only 17.

• Trace elements: Elements that are essential to life but required in extremely small amounts (e.g., iron, iodine).

Compounds

Compounds are substances formed when two or more different elements combine in a fixed ratio. Compounds have properties distinct from the elements that compose them.

• Compound: A substance consisting of two or more different elements combined in a fixed ratio.

• Compounds have characteristics different from those of their constituent elements.

• Most compounds contain at least three or four elements.

• Example: Water (H2O) is a compound made from hydrogen and oxygen.

Key Terms and Definitions

• Atom: The smallest unit of an element that retains the properties of that element.

• Essential elements: Elements required for an organism to survive, grow, and reproduce.

• Trace elements: Elements required by an organism in minute quantities.

Summary Table: Elements and Compounds

Term	Definition	Example
Element	Pure substance made of one type of atom	Oxygen (O), Carbon (C)
Compound	Substance made of two or more elements in a fixed ratio	Water (H2O), Carbon dioxide (CO2)
Trace Element	Element required in very small amounts for life	Iodine (I), Iron (Fe)

Additional info:

• Elements are organized in the periodic table according to their atomic number.

• Compounds are formed through chemical bonds, such as ionic or covalent bonds.