Chemistry - Molecules and their Composition

Free Course
Learn more about molecules and their composition.
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  • Duration

    2-3 Hours
  • Assessment

  • Certification

  • Publisher

    Khan Academy




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A molecule is a group of two or more atoms that bind together using chemical bonds. They may be from one or multiple elements and it is the ratio, or mass composition, of each molecule that gives the molecular compound its chemical characteristics. In this free online science course, you will learn about molecules and how they are composed of various elements, in mass, atoms and ratios. The course introduces the student to Avogadro’s number or the Mole, which is used to convert between atomic mass and grams, so that you will be able to work out ratios and weights of molecules. You will also learn how to balance chemical equations, and by balancing the reactants within equations, get viable chemical reactions. This branch of chemistry is known as Stoichiometry. The course will be of great interest to all students who wish to pursue a career in any of the sciences such as chemistry, physics, biology or geology, or the individual learner who simply wants to learn and understand how atoms form the molecules which make up all the material surrounding us.
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Learning Outcomes

Learning Outcomes:
- Understand the empirical, molecular and structural formulas;
- Use the Periodic Table and the amu to work out weights and ratios;
- Convert between Avogadro’s number (moles) and grams;
- Derive the empirical structure from mass composition;
- Balance an chemical equation.


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