FOSS Next Generation Mixtures and Solutions

Chemistry is the study of the structure of matter and the changes or transformations that take place within those structures. The Mixtures and Solutions Module introduces students to the properties, behaviors, and changes in substances—fundamental ideas in chemistry. Students also develop models to explain how something works.

Students make mixtures of water and solid materials and separate the mixtures with screens and filters. They find that water and salt make a special kind of mixture—a solution—which cannot be separated with a filter, but only through evaporation. Students are challenged with a problem: how to separate a mixture of three dry solid materials. The investigation concludes with students going outdoors to see what natural materials make solutions with water.

Students work with others as scientists and engineers to create conceptual and physical models to explain how something works.

Students observe and compare soft drink solutions that differ in the amount of powder (water held constant) and in the amount of water (powder held constant) to develop the concept of concentration. They make salt solutions of different concentrations and compare them, using a balance. Students determine the relative concentrations of three mystery solutions made from the same solid material by comparing the mass of equal volumes of the solutions. Finally, students layer salt solutions to determine their relative concentrations.

Students make a saturated solution by adding salt to water until no more salt will dissolve. They also make a saturated Epsom salts solution. Using a balance, they compare the solubility of the two solid materials by comparing the mass of the salt and Epsom salts dissolved in the saturated solutions. Students use the property of solubility to identify an unknown material. They analyze local water samples using separation techniques. Students engage in an engineering design challenge to remove salt from ocean water.

Students make three solutions with water, calcium chloride, baking soda, and citric acid. They systematically mix pairs of those solutions and observe changes that occur. The changes (formation of a gas and a white precipitate) are identified as evidence of a chemical reaction.