https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/v/elements 2025-01-16T17:32:17.772857468Z Elements Elements are the fundamental building blocks of all matter, just as letters form the basis of all writing. With only about 100 natural elements, nature constructs everything around us—from tiny microbes to vast oceans and stars. These elements, represented by symbols on the periodic table, combine in countless ways to create the diverse materials that make up the universe. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/7bad28ff-1c16-4904-860d-48ebd21ceb41_1280_720_base.png Elements Elements are the fundamental building blocks of all matter, just as letters form the basis of all writing. With only about 100 natural elements, nature constructs everything around us—from tiny microbes to vast oceans and stars. These elements, represented by symbols on the periodic table, combine in countless ways to create the diverse materials that make up the universe. https://cdn.kastatic.org/ka-youtube-converted/PeNjuIQFd9U.mp4/PeNjuIQFd9U.mp4 313 Elements, compounds and mixtures https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/v/atoms 2025-01-16T17:32:17.772857468Z Atoms An atom is the smallest particle of an element that still retains all the properties of that element. Early philosophers imagined atoms as indivisible units that make up all matter, an idea revived and developed by scientists like John Dalton. Atoms are incredibly small and numerous—a single gold ring contains more atoms than stars in the universe, highlighting their fundamental role in forming the matter we see. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/6f8dc03b-b8ae-49fe-b3c7-28487059ceae_1280_720_base.png Atoms An atom is the smallest particle of an element that still retains all the properties of that element. Early philosophers imagined atoms as indivisible units that make up all matter, an idea revived and developed by scientists like John Dalton. Atoms are incredibly small and numerous—a single gold ring contains more atoms than stars in the universe, highlighting their fundamental role in forming the matter we see. https://cdn.kastatic.org/ka-youtube-converted/KyBgxe-rU48.mp4/KyBgxe-rU48.mp4 248 Elements, compounds and mixtures https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/v/molecules-crystals-and-diatomic-elements 2025-01-16T17:32:17.772857468Z Molecules, crystals, and diatomic elements Elements and compounds can exist as pure substances, each with a fixed, definite composition. Some compounds, like water, are made of individual molecules. Others, like salt, form crystals—large, repeating 3D patterns without individual molecules. Additionally, some elements pair up as diatomic molecules, such as O₂ and H₂, rather than existing as single atoms. Understanding whether a substance is molecular or crystalline and how diatomic elements differ from compounds is key to classifying matter. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/61c8ef98-a62f-4bd5-bb36-dd0266f54967_1280_720_base.png Molecules, crystals, and diatomic elements Elements and compounds can exist as pure substances, each with a fixed, definite composition. Some compounds, like water, are made of individual molecules. Others, like salt, form crystals—large, repeating 3D patterns without individual molecules. Additionally, some elements pair up as diatomic molecules, such as O₂ and H₂, rather than existing as single atoms. Understanding whether a substance is molecular or crystalline and how diatomic elements differ from compounds is key to classifying matter. https://cdn.kastatic.org/ka-youtube-converted/thXilnp5UNQ.mp4/thXilnp5UNQ.mp4 367 Elements, compounds and mixtures https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/v/compounds-and-chemical-formulas 2025-01-16T17:32:17.772857468Z Compounds and chemical formulas Some substances, like copper or gold, are pure elements. Others, like water (H₂O), are compounds—made from two or more elements in fixed ratios, chemically bonded. Each compound has a unique formula, like CO₂ for carbon dioxide, representing its specific atomic arrangement. Compounds form molecules, tightly bonded units, creating an incredible diversity of substances in nature. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/e3e4181e-5236-462c-82b7-64099d59b95c_1280_720_base.png Compounds and chemical formulas Some substances, like copper or gold, are pure elements. Others, like water (H₂O), are compounds—made from two or more elements in fixed ratios, chemically bonded. Each compound has a unique formula, like CO₂ for carbon dioxide, representing its specific atomic arrangement. Compounds form molecules, tightly bonded units, creating an incredible diversity of substances in nature. https://cdn.kastatic.org/ka-youtube-converted/36nlbUdRvUM.mp4/36nlbUdRvUM.mp4 361 Elements, compounds and mixtures https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/v/types-of-mixtures-ms 2025-01-16T17:32:17.772857468Z Types of mixtures A mixture is a physical blend of two or more substances, unlike pure substances such as elements or compounds. Homogeneous mixtures are uniform throughout, with components evenly distributed at a molecular level, while heterogeneous mixtures have visible separation between components. Physical properties like density or solubility allow separation without a chemical reaction. Examples include salt water (homogeneous) and oil and water (heterogeneous). Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/fdb448a7-a551-4497-81f5-704e5ff938e0_1280_720_base.png Types of mixtures A mixture is a physical blend of two or more substances, unlike pure substances such as elements or compounds. Homogeneous mixtures are uniform throughout, with components evenly distributed at a molecular level, while heterogeneous mixtures have visible separation between components. Physical properties like density or solubility allow separation without a chemical reaction. Examples include salt water (homogeneous) and oil and water (heterogeneous). https://cdn.kastatic.org/ka-youtube-converted/rDWfLHn8PDM.mp4/rDWfLHn8PDM.mp4 340 Elements, compounds and mixtures https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/v/properties-of-homogeneous-mixtures 2025-01-16T17:32:17.772857468Z Properties of homogeneous mixtures Homogeneous mixtures, also known as solutions, have components that are evenly distributed at the molecular level without chemical bonding. Examples include salt water, air, and alloys like steel. Solutions consist of a solute dissolved in a solvent, and their properties can vary with concentration. Mixtures can be separated using physical properties, such as boiling points or magnetism, unlike compounds that require chemical changes to be separated. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/34f67b27-294c-4a5e-8834-7104aea5ada4_1280_720_base.png Properties of homogeneous mixtures Homogeneous mixtures, also known as solutions, have components that are evenly distributed at the molecular level without chemical bonding. Examples include salt water, air, and alloys like steel. Solutions consist of a solute dissolved in a solvent, and their properties can vary with concentration. Mixtures can be separated using physical properties, such as boiling points or magnetism, unlike compounds that require chemical changes to be separated. https://cdn.kastatic.org/ka-youtube-converted/oilrxnwowTs.mp4/oilrxnwowTs.mp4 363 Elements, compounds and mixtures https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/e/apply-elements-and-atoms 2025-12-18T18:00:52.364814749Z Apply: elements and atoms Apply your understanding of elements and atoms in this set of free, standards-aligned practice questions. donna exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/e/understand-compounds-and-chemical-formulas 2026-04-29T07:20:45.495372596Z Understand: Compounds and chemical formulas Check your understanding of compounds and chemical formulas in this set of free, standards-aligned practice questions. Allen Ruch exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/e/apply-compounds-and-chemical-formulas 2026-04-29T07:20:45.495372596Z Apply: Compounds and chemical formulas Apply your understanding of compounds and chemical formulas in this set of free, standards-aligned practice questions. Allen Ruch exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/e/understand-mixtures 2026-04-27T11:50:44.5708213Z Understand: Mixtures Check your understanding of mixtures and pure substances in this set of free, standards-aligned practice questions. DFigenshu exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/e/apply-mixtures 2026-04-29T07:20:45.495372596Z Apply: Mixtures Apply your understanding of heterogeneous and homogeneous mixtures in this set of free, standards-aligned practice questions. donna exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/a/compounds-and-chemical-formulas 2026-04-29T07:20:45.495372596Z Learn and try: Molecules, compounds, and chemical formulas Learn about how different elements combine to form compounds with entirely new properties and how these compounds can exist as molecules or crystals. article https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/a/elements-atoms-and-the-periodic-table 2026-04-17T11:10:45.679633951Z Learn and try: Elements, atoms, and the periodic table Learn about the basic building blocks of all matter and how atoms of different elements have unique properties. Discover how elements are organized on the periodic table and what makes each element distinct. article https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:atoms-elements-and-compounds/x8bc8fb44369617ed:elements-compounds-and-mixtures/a/mixtures 2026-04-29T07:20:45.495372596Z Learn and try: Mixtures Learn how to identify and distinguish between mixtures where components are evenly distributed versus those where components remain visibly separate. Explore different methods for separating mixtures based on the physical properties of their components. article