Summary
Highlights
Matter is categorized into two main groups: pure substances and mixtures. Pure substances consist of one type of substance, while mixtures are composed of two or more different pure substances combined.
Pure substances are further divided into elements and compounds. Elements like oxygen, helium, nitrogen, iron, and zinc are pure substances made of only one kind of atom. Compounds, such as water, sodium chloride, ethanol, and carbon dioxide, are also pure substances but are formed from two or more different elements chemically bonded together.
Mixtures are classified as either homogeneous or heterogeneous. A homogeneous mixture has a uniform composition throughout, where its components are evenly distributed. A heterogeneous mixture, conversely, does not have a uniform composition, and its components can be visually distinguished.
Examples of homogeneous mixtures include salt dissolved in water, which appears as a single clear solution, and air, which is a uniform blend of various gases like oxygen, nitrogen, and argon. Brass, a metal alloy, is also a homogeneous mixture.
Heterogeneous mixtures include oil and water, where the less dense oil floats on top, forming distinct layers. Sand and water also constitute a heterogeneous mixture, as the sand settles at the bottom, clearly separated from the water.