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Teacher Portal

Properties of Matter: Investigation 4 –

Lab

 

 

 

 

 

 

 

ZERO-IN

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.

MINDSET

This Investigation is designed to

  • promote student exploration of the property of pH,
  • introduce students to the Determination of pH Using pH paper procedure,
  • provide students an opportunity to discover that compounds can be acidic, basic or neutral, and
  • encourage student analysis of the relationship between elemental composition, compounds, and pH.

BE PREPARED

Teacher Preparation for the Investigation includes the following. This preparation should be done prior to students arriving in the lab.

  • Fill four 100 ml beakers with each of the following: baking soda, salt, vitamin, and sugar.
  • Fill three 400 ml beakers with vinegar, rubbing alcohol and vegetable oil.
  • Fill a one-liter pitcher with water for each group.
  • Place the materials at the distribution center.
  • Write the following compounds and their formulas on the board:

POM6_3_lab

  • Put all materials at the distribution area.
  • Divide the students into five cooperative groups.

Student Preparation for the Investigation includes having students gather the following materials. This preparation takes place on lab day after student groups have settled at their assigned lab tables.

Note: The materials are listed in students’ SDRs. They are also listed below for your reference.

  • (16) pH strips
  • (5) weigh dishes
  • (5) empty 400 ml beakers
  • (3) empty 100 ml beakers
  • (1) 100 ml graduated cylinder
  • (8) 2cm pieces of masking tape
  • (1) pH chart
  • (1) triple beam balance
  • (1) marker
  • (1) liter pitcher filled with 1000 ml of water
  • (1) pair of goggles for each student
  • (1) pair of vinyl gloves for each student
  • (1) glass stir rod
Direct one student from each lab group to collect the materials listed in their SDRs.

INVESTIGATE

  • Introduce the method of testing pH using the Determination of pH Using pH Paper procedure. Demonstrate with one of the liquid samples.
  • Discuss with students the concept that testing of pH can only be performed with liquid samples.
  • Demonstrate by placing the pH strip in solid salt. Show students that no color change occurs.
  • Dissolve ten grams of salt into a 400 ml beaker filled with 100 ml of water. Show students that pH can now be determined because the sample is in a solution.
  • Explain to students that during the lab, they will test the pH of both solid and liquid compounds.
  • Remind students that the solid compounds will have to be made into solutions before testing their pH.
  • Encourage students to reflect on the PreLab video as they move through the procedural steps.
  • Explain to students that during the Experiment, every procedural step is important. If one step is skipped, data can become invalid. To help students keep on track, direct them to read each step thoroughly, complete the step, then check it off (Read it – Do it – Check it off).
  • Direct students to complete procedural steps in their SDRs.
Note: The procedural steps are listed below for your reference. Teacher “Notes” are inserted, as needed, to help facilitate the lab.
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  1. Test the pH of the liquid compounds.
    1. Locate each liquid compound at the distribution center.
    2. Use a graduated cylinder to add 50 ml of a liquid compound to an empty 100 ml beaker.
    3. Use the tape and marker to label the beaker.
    4. Use the pH indicator strip to determine pH. You may also wish to refer to the Determination of pH procedure.
    5. Record: Write your results in Table A.

Note: Students should record their results in Table A of their Extension Investigation Data Record.

  1. Test the pH of the solid compounds. Solids must be made into solutions in order for the pH strips to be activated.
    1. Test the pH of the water with a pH indicator strip.
    2. Record: Write your results in Table A.
    3. Create a solution.
      • Pour 100 ml of water into a 400 ml beaker.
      • Add 10 grams of the solid compound.
      • You may wish to refer to the Triple Beam Balance Equilibration, Triple Beam Balance Use and Operation, and Measuring Mass Using a Weigh Dish or Beaker procedures.
      • Use tape and a marker to label the beaker.
      • Stir the solution for several minutes with a glass stir rod until the solid is completed dissolved.
    1. Dip a pH indicator strip into one of the beakers for 1 or 2 seconds.
    2. Remove the strip after 2 seconds and compare the colors to the indicator on the pH strip container.
    3. Record: Write your results in Table A.

Note: Students should record their results in Table A of their Extension Investigation Data Record.

POM4a

CLEAN UP

Let students know your expectations for clean up. Ask them to clean up.