Lesson 4: 1.4 Composition of Mixtures
Duration of Days: 1
Lesson Objective
Explain the quantitative relationship between the elemental composition by mass and the composition of substances in a mixture.
How do the particulate structures of pure substances and mixtures differ?
How can we determine the purity or percent composition of a mixture using elemental analysis?
Mixture
Pure Substance
Elemental Analysis
Percent Purity
Heterogeneous
Homogeneous
Learning Objective 1.4.A; Suggested Skill 5.A (Mathematical Routines)
Students will distinguish between pure substances (fixed proportions) and mixtures (variable proportions) at the particulate level. They will utilize mass percentage data of a specific element to determine the overall composition or purity of an impure mixture.
Support: Utilize particulate drawings (circle drawings representing atoms) to visually contrast a container of a pure compound versus a mixture of compounds.
Extension: Design a conceptual inquiry problem where students must determine the mass percent of an active ingredient (e.g., sodium bicarbonate) mixed with an inert substance, using mass loss data from heating.
A problem solving prompt where students are given the total mass of an impure sample and the mass of an isolated element/precipitate, requiring them to compute the mass percent purity of the original substance.