https://www.khanacademy.org/science/bridge-course-class-11th-chemistry/x426c9d2c554669cb:basic-concepts-of-chemistry/x426c9d2c554669cb:laws-of-chemical-combination/v/law-of-conservation-of-mass 2023-06-26T12:36:08.867767149Z Law of conservation of mass What happens to mass in a chemical reaction? Does it change or remain the same? Let's find out! Vibhor Pandey video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Law of conservation of mass What happens to mass in a chemical reaction? Does it change or remain the same? Let's find out! https://cdn.kastatic.org/ka-youtube-converted/rnpy_SHsMNg.mp4/rnpy_SHsMNg.mp4 180 Atoms and Molecules https://www.khanacademy.org/science/bridge-course-class-11th-chemistry/x426c9d2c554669cb:basic-concepts-of-chemistry/x426c9d2c554669cb:laws-of-chemical-combination/v/law-of-definite-proportions 2023-06-26T12:36:08.867767149Z Law of definite proportions If we take 10L of water or 10,000L of water, will the ratio of the mass of oxygen to hydrogen in both the samples be same or different? Let's find out! Vibhor Pandey video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Law of definite proportions If we take 10L of water or 10,000L of water, will the ratio of the mass of oxygen to hydrogen in both the samples be same or different? Let's find out! https://cdn.kastatic.org/ka-youtube-converted/IKbOoCrXXIk.mp4/IKbOoCrXXIk.mp4 139 Atoms and Molecules https://www.khanacademy.org/science/bridge-course-class-11th-chemistry/x426c9d2c554669cb:basic-concepts-of-chemistry/x426c9d2c554669cb:laws-of-chemical-combination/e/laws-of-chemical-combination 2026-04-07T09:22:30.618598699Z Laws of chemical combination (basic) Let's solve a few problems to understand the laws of chemical combination. Aanchal Arora exercise https://www.khanacademy.org/science/ap-biology/chemistry-of-life/elements-of-life/v/elements-and-atoms 2023-03-31T23:16:47.953017837Z Elements and atoms Elements are pure substances with specific properties. Atoms are the smallest units of elements that still retain the element's properties. Atoms contain electrons, neutrons, and protons. Each element is defined by the number of protons in its nucleus. Sal Khan video https://cdn.kastatic.org/googleusercontent/zfLHeNHjPfEhSYfKtZLu6Ft_uFg2p_L9gALjUyfahbjdBzZbrDLxrg-rk_mrsUBBVIKs44ALBBI1Gv8cm2O_Ppa05g Elements and atoms Elements are pure substances with specific properties. Atoms are the smallest units of elements that still retain the element's properties. Atoms contain electrons, neutrons, and protons. Each element is defined by the number of protons in its nucleus. https://cdn.kastatic.org/ka-youtube-converted/IFKnq9QM6_A.mp4/IFKnq9QM6_A.mp4 789 Atoms and Molecules https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-bonding/x2613d8165d88df5e:ionic-nomenclature/v/naming-ions-and-ionic-compounds 2022-10-26T22:01:10.867792203Z Naming ions and ionic compounds Ionic compounds are neutral compounds made up of positively charged ions called cations and negatively charged ions called anions. For binary ionic compounds (ionic compounds that contain only two types of elements), the compounds are named by writing the name of the cation first followed by the name of the anion. For example, KCl, an ionic compound that contains K⁺ and Cl⁻ ions, is named potassium chloride. video https://cdn.kastatic.org/googleusercontent/F9fhxeAzbl5tczOC_KxI5UnfufCJyVdO9qXgu-Rltqyf00aQlHvx_6KjnT27peERAhBSPipQTUL_5Zz001iLpgdW Naming ions and ionic compounds Ionic compounds are neutral compounds made up of positively charged ions called cations and negatively charged ions called anions. For binary ionic compounds (ionic compounds that contain only two types of elements), the compounds are named by writing the name of the cation first followed by the name of the anion. For example, KCl, an ionic compound that contains K⁺ and Cl⁻ ions, is named potassium chloride. https://cdn.kastatic.org/ka-youtube-converted/ptAw20kem90.mp4/ptAw20kem90.mp4 237 Atoms and Molecules https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-bonding/x2613d8165d88df5e:ionic-nomenclature/v/naming-ionic-compound-with-polyvalent-ion 2021-03-18T10:33:23Z Naming ionic compound with polyvalent ion Naming ionic compounds that contain polyvalent ions, using example of cobalt (III) sulfide. video https://cdn.kastatic.org/googleusercontent/sxisshpuJ9O_2ZZjQvIjFGtLso07gFMAoyk38AXaNrm0p6xisnDoq1wep1D35GeS_-3QwEcEQ-Q_Wx31ltj-MCoE Naming ionic compound with polyvalent ion Naming ionic compounds that contain polyvalent ions, using example of cobalt (III) sulfide. https://cdn.kastatic.org/ka-youtube-converted/vVTwzjvWySs.mp4/vVTwzjvWySs.mp4 242 Atoms and Molecules https://www.khanacademy.org/science/bridge-course-class-11th-chemistry/x426c9d2c554669cb:basic-concepts-of-chemistry/x426c9d2c554669cb:ionic-compounds/e/naming-ionic-compounds 2026-03-29T17:54:23.483136198Z Naming ionic compounds Practice naming ionic compounds when given the formula Yuki exercise https://www.khanacademy.org/science/tg-grade-10-physical-science-grade-course/x78128e17d2b1909f:atoms-and-molecules/x78128e17d2b1909f:molecules-and-ions/v/finding-the-formula-of-an-ionic-compound 2025-05-29T08:44:44.739717086Z Finding the formula of an ionic compound To find the formula of an ionic compound, we first identify the cation and write down its symbol and charge. Then, we identify the anion and write down its symbol and charge. Finally, we combine the two ions to form an electrically neutral compound. In this video, we'll walk through this process for the ionic compound calcium bromide. Dubverse video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Finding the formula of an ionic compound To find the formula of an ionic compound, we first identify the cation and write down its symbol and charge. Then, we identify the anion and write down its symbol and charge. Finally, we combine the two ions to form an electrically neutral compound. In this video, we'll walk through this process for the ionic compound calcium bromide. https://cdn.kastatic.org/ka-youtube-converted/-OVGvVUO2Us.mp4/-OVGvVUO2Us.mp4 178 Atoms and Molecules https://www.khanacademy.org/science/bridge-course-class-11th-chemistry/x426c9d2c554669cb:basic-concepts-of-chemistry/x426c9d2c554669cb:ionic-compounds/v/worked-example-formula-for-an-ionic-compound 2023-06-26T12:36:08.867767149Z Worked example: Formula for an ionic compound Let's understand how to write the formula for ionic compounds! Vibhor Pandey video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Worked example: Formula for an ionic compound Let's understand how to write the formula for ionic compounds! https://cdn.kastatic.org/ka-youtube-converted/rjsx6MP0Vos.mp4/rjsx6MP0Vos.mp4 211 Atoms and Molecules https://www.khanacademy.org/science/bridge-course-class-11th-chemistry/x426c9d2c554669cb:basic-concepts-of-chemistry/x426c9d2c554669cb:ionic-compounds/e/find-the-formula-for-ionic-compounds 2025-02-06T18:17:42.147590351Z Find the formula for ionic compounds Practice finding the formula when given the name of an ionic compound. Yuki exercise https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:atoms-and-molecules/x46dd29ce84a663ea:writing-chemical-formulae/e/predicting-the-formula-of-the-given-ionic-compound 2026-03-06T09:40:40.837655949Z Predicting the formula of the given compound Let's solve a few problems to identify the correct formula of a given ionic compound. Aanchal Arora exercise https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:atomic-structure-and-properties/x2eef969c74e0d802:moles-and-molar-mass/v/the-mole-and-avogadro-s-number 2022-09-07T08:21:01.673602243Z The mole and Avogadro's number One mole of a substance is equal to 6.022 × 10²³ units of that substance (such as atoms, molecules, or ions). The number 6.022 × 10²³ is known as Avogadro's number or Avogadro's constant. The concept of the mole can be used to convert between mass and number of particles. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/6088ce39-bf63-44b0-8918-4702d0c7bf46_1280_720_base.png The mole and Avogadro's number One mole of a substance is equal to 6.022 × 10²³ units of that substance (such as atoms, molecules, or ions). The number 6.022 × 10²³ is known as Avogadro's number or Avogadro's constant. The concept of the mole can be used to convert between mass and number of particles. https://cdn.kastatic.org/ka-youtube-converted/cvi4IJMZ13Q.mp4/cvi4IJMZ13Q.mp4 537 Atoms and Molecules https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:atoms-and-molecules/x46dd29ce84a663ea:molecular-mass-and-mole-concept/v/worked-example-calculating-molecular-weight 2023-06-26T12:36:08.867767149Z Worked example: Calculating Molecular weight Let's understand how to calculate the molecular weight of a molecule! Vibhor Pandey video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Worked example: Calculating Molecular weight Let's understand how to calculate the molecular weight of a molecule! https://cdn.kastatic.org/ka-youtube-converted/o76Kg0-4AJI.mp4/o76Kg0-4AJI.mp4 208 Atoms and Molecules https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:stoichiometry-and-the-mole/x2613d8165d88df5e:moles-and-molar-mass/v/worked-example-calculating-molar-mass-and-number-of-moles 2022-09-07T08:21:01.673602243Z Worked example: Calculating molar mass and number of moles The molar mass of a substance is the mass in grams of 1 mole of the substance. As shown in this video, we can obtain a substance's molar mass by summing the molar masses of its component atoms. We can then use the calculated molar mass to convert between mass and number of moles of the substance. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/a85d2606-e7fa-4f30-be42-548a6905d16d_1280_720_base.png Worked example: Calculating molar mass and number of moles The molar mass of a substance is the mass in grams of 1 mole of the substance. As shown in this video, we can obtain a substance's molar mass by summing the molar masses of its component atoms. We can then use the calculated molar mass to convert between mass and number of moles of the substance. https://cdn.kastatic.org/ka-youtube-converted/PAqzpZ-nMlg.mp4/PAqzpZ-nMlg.mp4 349 Atoms and Molecules https://www.khanacademy.org/science/grade-9-chemistry-snc-aligned/x22d5b83c2ea2dc38:stoichiometry/x22d5b83c2ea2dc38:the-mole-and-molar-mass/e/converting-moles-and-mass 2026-04-07T09:22:30.618598699Z Converting moles and mass Practice converting moles to grams, and from grams to moles when given the molecular weight. Yuki exercise