Matter is anything that has mass and takes up space. Everything that we see around us is made up of matter. It can be described and identified based on its physical and chemical properties. ^[1-4]

Physical properties are those we can observe or measure without changing the substance itself. These include color, state (solid, liquid, gas), density, melting and boiling points, and solubility. For example, we can tell a banana is yellow, ice melts at 0°C, and sugar dissolves in water – all without altering the substance’s composition.

Chemical properties, on the other hand, describe how a substance interacts with other substances and can only be observed during a chemical change. These include reactivity (like iron forming rust), flammability (whether something can burn), and acidity or basicity (like vinegar being acidic).

Classification of Matter According to Composition

Scientists classify matter not only by its appearance or behavior but also by its composition and how it changes, leading to its classification into pure substances and mixtures. ^[1-7]

Pure Substances

A pure substance is a type of matter that is made of only one kind of material. It has the same properties everywhere, no matter where you find it. Pure substances cannot be separated into different parts by physical methods like filtering or stirring. There are two main types of pure substances: elements and compounds.

Elements

An element is the simplest type of pure substance. It is made up of only one type of atom. Elements cannot be broken down into anything simpler. There are more than 100 known elements, and they are all listed in the Periodic Table.

Examples

Gold (Au), oxygen (O₂), iron (Fe), and hydrogen (H₂) are all different elements. Some elements, like gold and silver, are metals, while others, like oxygen and nitrogen, are gases. 

Compounds

A compound is a pure substance made when two or more different elements join together chemically. Unlike mixtures, the elements in a compound do not keep their original properties – they form something new. 

Examples

Water (H₂O) is a compound made of hydrogen and oxygen, but it does not behave like either gas. Similarly, table salt (NaCl) is made from sodium (a metal) and chlorine (a poisonous gas), yet together they form something safe to eat.

Pure substances are important in science and everyday life. Elements like oxygen help us breathe, and compounds like water are essential for survival. 

Mixtures

A mixture is made of two or more substances that are combined but not chemically joined together. This means that each part of a mixture has its properties, and we can often separate them again. There are two main types of mixtures: homogeneous mixtures and heterogeneous mixtures.

Homogeneous Mixture

A homogeneous mixture is a mixture where the substances are evenly spread out, and you cannot see the different parts. It looks the same all the way through. 

Examples

Saltwater is a homogeneous mixture because the salt dissolves completely in the water. Air is a mixture of different gases. Milk is a mixture of water, fats, and proteins that appears uniform.

Heterogeneous Mixture

A heterogeneous mixture is a mixture where the substances are not evenly spread out, and you can see the different parts.

Examples

A bowl of salad, where you can see the lettuce, tomatoes, and cucumbers separately. When sand and water are mixed, the sand settles at the bottom instead of dissolving. Other examples include trail mix, oil and water, and a bowl of cereal with milk.

After understanding how matter is classified based on its chemical composition, the next step is to explore how its physical state can also classify it.

Classification of Matter According to Physical State

Matter exists in different forms called states of matter. The most common states are solid, liquid, and gas. There is also a fourth state called plasma, which we usually see in special places like the Sun or lightning. ^[1-7]

Solids

A solid has a fixed shape and size. The particles in a solid are packed closely together and can only vibrate in place. This is why solids feel hard and keep their shape. Examples of solids include rocks, pencils, and ice.

Liquids

A liquid has a definite volume but no fixed shape. It takes the shape of its container. The particles in a liquid are close together, but they can slide past each other, which allows liquids to flow. Examples include water, milk, and juice.

Gases

A gas does not have a fixed shape or volume. Gases spread out to fill the space they are in. The particles in a gas are far apart and move around freely in all directions. Examples of gases include oxygen, carbon dioxide, and the air we breathe.

Plasma

Plasma is a special state of matter made of very high-energy particles. It is found in the Sun, stars, lightning, and neon signs. Plasma is not common in everyday life, but it makes up most of the universe!