Matter

Chemistry explores 'stuff' or matter, which is anything with mass and volume. Mass is the amount of matter and volume is the space occupied by matter. Mass can be measured with a balance, and volume can be measured mathematically for regular shapes or through water displacement for irregular shapes.

Matter is divided into substances and mixtures. Substances are pure and have uniform composition, like copper or water. Physical properties are qualities that can be observed or measured without changing the substance's composition, such as melting point, state at room temperature, color, and boiling point. These properties help differentiate substances, like ethanol and water.

There are three primary states of matter: solids, liquids, and gases. Solids have a definite shape and volume with tightly packed, incompressible particles. Liquids have an indefinite shape, fixed volume, and flowing particles that are slightly compressible. Gases have indefinite shape and volume, with high-energy particles spaced far apart, making them highly compressible. A vapor is a gaseous form of a substance that is normally a liquid or solid at room temperature.

A physical change alters a material's physical properties without changing its chemical composition. Examples include boiling, melting, freezing, crushing, condensing, splitting, cutting, and grinding. Some physical changes are reversible, like melting ice, while others are irreversible, like cutting hair.

Mixtures are physical blends of two or more components. Homogeneous mixtures are uniform throughout (e.g., air, milk), having one phase. Heterogeneous mixtures are not uniform and show distinct parts (e.g., granite, oil and water), having two or more phases.

Mixtures can be separated based on differences in their physical properties using various methods like magnets, filtration (separating solids from liquids), evaporation, distillation (separating liquids with different boiling points), chromatography, flotation, and sieving. Filtration uses a filter to separate solids, while distillation uses boiling and condensation to separate liquids.

Pure substances are divided into elements and compounds. Elements are the simplest form of matter with unique properties, composed of single atoms or molecules of the same element. Compounds are substances containing two or more elements chemically combined in fixed proportions, like water (H2O). Chemical changes break compounds down into elements or rearrange atoms to form new substances with different compositions and properties.

Matter is categorized into substances and mixtures. Substances further divide into elements and compounds. Mixtures are either homogeneous or heterogeneous. Mixtures can be physically separated into substances, and compounds can be chemically separated into elements.