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Properties of Matter: Investigation 4 –

Concept Day








Properties of Matter: Investigation 4

Concept Day




  • Tell students that this final Investigation of the CELL Properties of Matter concludes with experiments involving another chemical property of matter, pH.

Note: While pH is actually a measure of the hydrogen ion concentration of a solution, we do not wish to confuse students with the concept of ions at this point. Students will learn much more about pH in the seventh-grade CELL Acids and Bases and at various other steps along the way.



Tell students that:

    • pH is used to describe whether a compound is an acid, base or neutral,
    • the range of the pH Scale is from 0 to 14,
    • substances with a pH below 7 are called acidic,
    • substances with a pH above 7 are called basic, and  
    • substances with a pH of 7 are called neutral.

Note: The teacher may be interested to know that pH is actually a concentration measurement of the amount of dissolved hydrogen ions (H+) in a solution. Since the pH Scale is logarithmic, it represents an enormous range in hydrogen ion concentration.



  • Tell students that this slide depicts the pH Scale and highlights the pH of a number of common compounds that may be familiar with.
  • Read the slide to students.

Note: If there is enough time, and students can get online, the pH of additional common compounds may be “Googled” and discussed.

Note: It is interesting to note that blood, saliva, tears, and other body fluids are near neutral as is the pH of seawater. As life on Earth likely originated in the sea, perhaps this is not a coincidence.



  • Read the slide to students.

  • Tell students that although they will not be using the type of concentrated acids and bases that cause these types of chemical burns, they need to treat all chemicals as though they were dangerous. 
    • Note: As this is the first CELL of middle school, where students will begin to come into contact with acids and bases in LabLearner, this and the next slide are meant to draw attention to lab safety.

      Note: The images are graphic but instructive. While most students suspect that acid can burn skin, they may not have considered that compounds at both extremes of the pH Scale can be hazardous.

      Note: Students are more likely to come into contact with stronger compounds in the garage, kitchen, and laundry room.

    SLIDE POM6-4-5

    Note: This slide shows the proper protection to use when working in the lab. Notice that goggles are worn to cover the eyes, not the top of the head.

    • Read the slide to students.
    • Warn students that they should avoid touching their eyes or other body areas while wearing safety gloves.
    • Tell students to wash their hands after removing safety gloves to remove any talcum powder that might cause irritation.

    Note: Hopefully these couple of slides will convince students that working in the lab is not only fun, but is serious business as well.


    SLIDE POM6-4-6

    Tell students that this slide illustrates two common methods of determining the pH of a solution:

    • The pH meter on the left is found in nearly all commercial and research labs. pH readings using this type of instrument is both accurate and fast.
    • pH paper on the right is less expensive than pH meters and is much easier to maintain.

    Note: pH meters use probes that have a membrane similar in some respects to the ones used on LabLearner oxygen meters. The probes must be kept wet and calibrated prior to use.

    Note: A pH strip is dipped into a solution and then the resultant color is compared to a reference guide as shown here. Sometimes, when the color of the activated strip appears to be between two colors on the guide, a student may report the pH as something like 5.5. While our pH readings in this Investigation do not require extreme accuracy, keep in mind that a reported reading of 5.5 really means “more than 5 and less than 6”.


    SLIDE POM6-4-7

    Note: If time permits, this final slide lists some of the highlights of the CELL Properties of Matter for grade 6. It can serve as a background for any number of discussions at the end of this CELL or as a review at a later time.