States of matter and mixtures Study Guide

Matter exists primarily in three states: solid, liquid, and gas. The transitions between these states are known as interconversions, and they are classified as physical changes. Unlike chemical reactions, which alter the chemical composition of a substance to form new substances, physical changes only affect the physical properties (like state, shape, or density) but not the chemical identity. For example, melting ice into water changes its physical state but it remains H₂O. These changes are reversible and do not involve breaking or forming new chemical bonds. Key interconversions include melting, freezing, boiling, condensation, sublimation, and deposition.

Paper chromatography is a technique used to separate mixtures of soluble substances. It relies on the differential movement of components within a mixture through a stationary phase (the paper) by a mobile phase (a solvent). When a solvent moves up the chromatographic paper, it carries the soluble substances with it. Different substances have varying affinities for the stationary phase and the mobile phase. Substances that are more soluble in the solvent and have weaker interactions with the paper will travel further up, while those less soluble in the solvent and with stronger interactions with the paper will travel shorter distances. This difference in movement allows for the separation of the mixture's components into distinct spots or bands on the paper.