Teacher Portal

Properties of Matter: Investigation 2 –










Italicized font represents information to be shared orally or physically completed with the students at this time.

The non-italicized font represents additional information included to support the teacher’s understanding of the content being introduced within the CELL.


Remind students that by observing a sample of matter and measuring its chemical and physical properties, we gradually acquire enough information to characterize it and distinguish it from other kinds of matter. This is the first step in the development of chemical science, in which interest is focused on specific types of matter.


Remind students that chemists may develop a synthetic fiber that can stop a speeding bullet or figure out how to make hair-styling gel work better.


Inform students that the Investigation is designed to help them to answer the following Focus Questions: 

  • Can you tell the difference between an element and a compound by calculating density and observing chemical reactions? It is likely that students will not be able to discern the difference between substances that are elements and those that are compounds during the course of their investigation.
  • Can you determine the identity of an unknown substance by calculating its density and observing chemical reactions? Students may or may suggest possible identities of the substances based on similarities of color and texture to substances that they encounter in everyday life.

Note: These questions are located in students’ SDRs at the beginning and end of the Investigation.

Note: These are succinct responses to the Focus Questions and are placed here for your reference at this time. Fully developed responses to the Focus Questions can be found on the PostLab page.


As a class, read the Background(s) in the Investigation. Have students read the information aloud or silently to themselves. When students have finished, discuss the following concepts as a class:

  • Density is a property of matter that defines how much matter exists in a particular space.
  • The density of matter depends on two things, mass and volume.
  • Density can be calculated by using the formula: Density = Mass ÷ Volume.
  • Chemical reactivity is a property of elements and compounds.
  • A chemical reaction can occur when an element or compound is combined with another element or compound.
  • Two signs of a chemical reaction are a change in color or formation of a gas (bubbles).

Note: These concepts are integrated into the Background(s) and are used to deepen students’ comprehension of the big ideas.


The following list includes Key Terms that are introduced in the Investigation Background(s). They should be used, as appropriate, by teachers and students during everyday classroom discourse.

  • density

Note: Definitions to these terms can be found on the Introduction page to the CELL.

Note: Additional words may be bolded within the Background(s). These words are not Key Terms and are strictly emphasized for exposure at this time.


  • Explain to students that they will continue to investigate the six unknown samples. As a part of their investigation, they will explore another physical property of matter, density, and some chemical properties of matter.
  • Complete the Recall section in students’ SDRs.
  • Review the difference between physical and chemical properties and changes with students, stressing the change in chemical composition during a chemical change and simply a change in form during physical changes.
  • Tell students that in the next part of their investigation they will see whether chemical reactions can show them if two physically different samples are actually the same substance.
  • Tell students that the second experiment may show them changes because the substances may react with one another. 
  • Ask students what they already know about changes. 
    • How are physical changes and chemical changes different? 
    • Can you think of an example of a physical change? 
    • Can you think of an example of a chemical change?
  • Play the video below. Stop to ask students questions or answer students’ questions when necessary. Remind students to follow along with their SDRs and make any notes that they think might be helpful.
  • After the video, direct students to divide into their lab groups to discuss their strategy for the lab. For example, they may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow students to anticipate the laboratory experience they will soon encounter. Students should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.


Tell students that they should review the Investigation in preparation for the Lab.