Who dunnit!? What is it? Science mysteries - in this case using mystery powders or liquids - give students a way to apply their understanding of properties of matter to a real-world problem. In this lesson, students explore physical and chemical properties of matter through stories, demonstrations and investigations with the objective of using properties of matter to identify different types of matter. This investigation is a precursor lesson to helping students to meet the Matter and its Interactions performance indicator: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred (MS-PS1-2).
While students conduct this investigation to produce data to serve as the basis for evidence that meet the goals of the investigation (SP3), they analyze and interpret data to provide evidence for phenomena (SP4) and apply scientific ideas, principles, and/or evidence to construct, revise and/or use an explanation for real-world phenomena, examples, or events (SP6). Throughout this process, students explore how properties of matter are related to the structure of matter and that structures can be designed to serve particular functions by taking into account properties of different materials, and how materials can be shaped and used (CCC). Also, students recognize that macroscopic patterns are related to the nature of microscopic and atomic-level structure (CCC).
The Properties of Matter Investigation series of lessons is a scientific inquiry investigation taught over the span of several days. To help manage the magnitude of this activity, you will find the project split into 2 parts.
The EXTEND stage allows students to apply new knowledge to a novel situation. The novel situation in this case is to create chemical profiles (observable physical and chemical properties) of known powders and liquids using microchemistry (chemistry on a small scale). For example profiles: Properties of Matter Investigation - Student Work or Properties of Matter Chemical Profile Teacher Notes Then using those profiles, students identify an unknown mystery powder or liquid. This process is shown in this Microchemistry Demonstration video:
To make the investigation even more engaging, the mystery substance could be part of a narrative as illustrated in this lesson: Virtual Collaboration: Vertical Lab Groups. For more on "making mysteries" to engage students, read this section's reflection: Building the Mystery.
Students use very small amounts of each powder and each liquid being sure to mix only one powder and one liquid at a time. As students observe the physical and chemical properties of the chemicals, they record their findings in Part IV of the Properties of Matter Investigation Student Handout data table.
When students have compiled their data, there are several options for continuing the investigation:
1) Analyze their data to determine the mystery liquid or powder based on the observed physical and chemical properties (Part V) while using the Clear Liquids Physical and Chemical Properties Chart (or a similar chart of powders) and continue on to the EVALUATE section of the lesson.
2) Complete the Hot and Cold Investigation to determine the freezing and boiling point of the mystery chemical (if it is a liquid). These extensive physical properties are useful when attempting to identify the type of matter the mystery chemical is composed of. Students then complete the steps as outlined above in Option 1.
3) Conduct additional investigation or research as suggested in Part VI. Students propose different tests they would like to do in order to collect more data. Calculating density and testing for flammability are popular proposals. This is also an opportune time to provide students with the Material Safety Data Sheets (MSDS) for the different chemicals (Science Lab). These data sheets include a wealth of in formation in addition to listing physical and chemical properties of matter. Students then complete the steps as outlined above in Option 1.
Teacher Note: Depending on your student's prior experiences, it is possible to use many different powders such as: baking soda, baking powder, sugar, sand, salt or starch and liquids, such as: water, salt water, iodine, vinegar (acid) or isopropyl alcohol. Be sure to understand the possible chemical reactions and safety precautions associated with each chemical. As always, it is imperative that students understand that reacting or mixing any chemical can result in unexpected reactions. For safety, students should wear goggles and be monitored closely for safe chemistry practices.
The EVALUATION stage is for both students and teachers to determine how much learning and understanding has taken place. To balance group versus individual accountability in assessment of the learning objectives related to physical and chemical properties, this lesson includes two options:
1) Properties of Matter Investigation Final Project. This project is a creative group assessment in which students create a page in the spirit of Paper Skyscrapers to present a claim and evidence about the identity of their mystery chemical: Final Project Student Work. Groups present their projects by reading their page and having other groups guess the mystery chemical.