Introduction to the Concepts of Matter, Composition, and Properties in Chemistry

The definition of chemistry typically includes matter, composition, and properties, which together relate to the study of the composition and properties of matter. In the following sections, we will explore these concepts to gain a deeper understanding of chemistry.

Matter refers to anything that occupies space and exhibits mass and inertia. All humans and objects around us consist of matter. Gases in the atmosphere also qualify as matter despite being invisible. Sunlight, on the other hand, is a type of energy, which we will discuss later.

Composition refers to the different parts or components of matter and their relative proportions. For instance, water contains hydrogen and oxygen in fixed proportions. Chemists describe the composition of water as 11.19% hydrogen and 88.81% oxygen by mass. Hydrogen peroxide is another example of a substance with a different composition of 5.93% hydrogen and 94.07% oxygen by mass.

Properties are the qualities or attributes that differentiate one sample of matter from another. Properties are classified as physical and chemical. Physical properties do not change the composition of a sample of matter. Examples of physical properties include color, malleability, and ductility. Chemical properties, on the other hand, involve a change in composition, such as the ability to react with another substance.

Physical changes occur when matter undergoes a transformation in its physical appearance without altering its composition. Freezing water to make ice is an example of a physical change. In contrast, chemical changes involve a transformation in the composition of matter. For instance, burning paper changes its composition by producing new gases.

Chemical properties are unique to each substance and define their behavior when reacting with other substances. Zinc reacts with hydrochloric acid to produce hydrogen gas and a solution of zinc chloride in water, which is one of its chemical properties. On the other hand, gold is chemically inert and does not react with hydrochloric acid. Understanding the differences in chemical properties helps us understand why certain materials are used for specific applications.

When sulfur is hammered, it crumbles into a yellow powder, as seen in the image on the left. Copper, on the other hand, can be found in large lumps of native copper, formed into pellets, hammered into thin foils, or drawn into wires, as shown in the image on the right.

When hydrochloric acid reacts with a zinc-plated nail, it produces bubbles of hydrogen gas that can be seen on the nail's surface. However, a gold bracelet remains unaffected by hydrochloric acid. In the photograph, the zinc plating has been consumed, revealing the underlying iron nail, which also reacts with hydrochloric acid and imparts some color to the acid solution.