Matter

Study of atomic structure, states of matter, and particle behavior forming the foundation of all chemistry.

Atoms are the tiny particles that make up all matter. Every element is composed of one type of atom, and atoms are too small to see with the naked eye or even an ordinary microscope.

A chemical experiment is a planned investigation that tests a hypothesis using controlled conditions. Learning to design, carry out, and record experiments is a fundamental scientific skill.

Chemistry is not confined to laboratories — it is happening all around you, every moment of the day. From the food on your plate to the screen you are reading this on, chemistry explains how the world works.

The chemistry laboratory is where scientists design and carry out experiments. Understanding its equipment and safety rules is essential before any practical work can begin.

Electrons occupy shells (energy levels) around the nucleus. The arrangement of electrons in these shells — called electronic configuration — determines how an element behaves chemically and reacts with other elements.

An element contains only one type of atom and cannot be broken down into simpler substances. A compound contains two or more different elements chemically bonded together and has different properties from the elements it was made from.

An ion is a charged atom or group of atoms that has gained or lost electrons. When metals and non-metals react, they transfer electrons to form positive and negative ions that attract each other — this is ionic bonding.

Isotopes are atoms of the same element that have different numbers of neutrons. They have the same chemical properties but different masses. Some isotopes are radioactive, while others are stable.

Molecules are formed when two or more atoms bond together. They can be made of atoms of the same element or different elements, and their properties differ from the individual atoms they are made of.

Every atom has a nucleus containing protons and neutrons, surrounded by electrons. The number of protons determines which element an atom belongs to and gives it its chemical identity.

Chemistry is the science of matter — what substances are made of, how they behave, and how they change. It underpins almost everything in the world around us, from the food we eat to the medicines that keep us healthy.

Air is not a single substance — it is a mixture of several gases. Understanding what air is made of and what each component does helps us understand breathing, weather, and life on Earth.

Human activity has changed the composition of Earth's atmosphere in ways that harm both the environment and human health. Understanding air pollutants and their effects is the first step toward solving these problems.

Matter changes from one state to another when energy (heat) is added or removed, causing particles to move faster or slower — these changes have specific names like melting, freezing, evaporation, and condensation.

Density is a measure of how much mass is packed into a given volume. Dense materials have particles packed closely together. Density explains why some objects sink and others float, and why gases are much lighter than solids or liquids.

Diffusion is the net movement of particles from an area of high concentration to an area of low concentration. It happens because particles are always moving randomly, and explains how smells travel, how oxygen moves into blood, and how substances move in and out of cells.

Gas pressure is caused by gas particles colliding with the walls of their container. Pressure increases when particles move faster (higher temperature) or are squeezed into a smaller space (lower volume). Understanding gas pressure is essential in everyday applications from tyres to weather systems.

Gases have no fixed shape or volume — their particles move rapidly in all directions and spread out to fill whatever container they are in.

Liquids have a fixed volume but no fixed shape — their particles are close together but free to move past each other, allowing liquids to flow and take the shape of their container.

Every substance has a specific melting point and boiling point — temperatures at which it changes state. These fixed temperatures are used to identify pure substances.

Solids have a fixed shape and volume because their particles are tightly packed in a regular arrangement and can only vibrate in place.

Water is one of the most remarkable substances on Earth. Its unique physical and chemical properties make life possible and shape our entire planet.