Unit 8 Quantitative Review

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Objective

Students will be able to demonstrate the ability to solve various mathematical problems related to Unit 8 through performing practice questions with partners and completing a pH calculation lab.

Big Idea

Being able to solve problems using chemical equations is critical for success in chemistry. This includes plugging into equations related to acid and base solutions.

Introduction

In this lesson students are taking what they have learned about solutions and acids/bases and demonstrating their understanding through performing partner practice and a pH calculation lab. 

  • This lesson does not align with any specific performance expectations with the Next Generation Science Standards; however, it is important that students understand how to characterize solution concentration and acidity with calculations.  This is a skill that is transferable to math class with problem solving and a skill that students will need for college-level science courses. 
  • This lesson aligns with the Next Generation Science and Engineering Practice 5: Using Mathematics and Computational Thinking.  It does so because students are solving problems related to solutions and pH.
  • This lesson aligns with the Next Generation Science and Engineering Practice 3: Planning and Carrying out Investigations.  It does so because students are performing a lab activity where they are measuring the pH of various solutions.

For the lab activity each group needs:

  • A well plate or other type of container to hold 6 different substances
  • 6 different substances (I use coke, sprite, apple juice, pinesol, baking soda solution, and soap).
  • Different ways of measuring pH.  I give students pH paper, a pH meter, and a pH probe.

Elaborate Part I

30 minutes

I begin this lesson by having students review what they learned about acid/base calculations.  This activity builds on the prior lesson, Acid and Base Calculations, where students learned about the equations that related pH, pOH, H+, and OH-.

  • I begin by passing out the Acid and base calculation lab to students.  I then give students instructions on how they will be doing the activity.  
  1. I first tell them that they will be testing 6 solutions.
  2. I then tell them that they will first predict if each solution is an acid or base.
  3. Next, I go over how they will determine the pH for each solution in one of three ways (pH meter, pH probe, or pH paper).  I also show students how to use pH paper.
  4. I tell them that once they have the pH that they will perform a calculation to figure out another quantity for each solution.
  5. Finally, I explain to students that they will record a conclusion in terms of whether the solution is an acid or base. 
  6. I then have students go up to a lab station with their table groups.  This is a picture of what a station looks like. 
  • This movie shows me going over the activity with students. 
  • As students are working I walk around to make sure that they are making predictions first, that they are using various methods to measure pH, and that they are solving for the different quantities correctly.  The biggest struggle of students is figuring out OH- so I usually have to show students the equations and have them realize that they first need to figure out pOH, and then can find OH-. 
  • This is a copy of one student's completed lab. 

Elaborate Part II

60 minutes

In this section part of the lesson I have students perform partner appointments to review the math that we have done in the unit.  

  • I begin this by passing out the partner math paper to students. 
  • I then have students make partners.  For more details on how I do this see my reflection on partner appointments. 
  • After students have partners I tell them that to do this activity they are going to need their Reference Sheet on the back of the Periodic Table.  I go over the equations that they will need in the activity.  This picture shows the reference sheet with the highlighted equations.
  • I then have students go to their first appointment (Appointment A) and show them slide 2 of the Partner Practice Presentation which has questions 1 and 2.  
  • This movie shows how I get students working with their partners. 
  • As students are working I walk around and check that they are on task and make sure that they are understanding how to do the problems.
    • This movie shows me helping a group with figuring out which equation to use. 
    • In this movie I am helping students figure out what to use as the solute/solvents in the equation.
  • As students are working I give hints on the board as to how to solve the problems for struggling students.  I do this so that I can help multiple groups at the same time.  This movie shows me beginning to help students.
  • As students are completing their questions with their partner I go over the answers on the board as I show in this movie
  • When students are done with their first appointment I continue with the 3rd slide and have them go to Appointment B for questions 3 & 4, then Appointment C for questions 5 & 6, and then finally Appointment D for questions 7 & 8.
  • This is a copy of one student's completed partner paper
  • There are several areas where students have difficulty in this activity.  
    • With both the solution and pH problems some students get confused as to which equation to use.  To help students I remind them to use the problem solving technique of underlining what they know, circling what they want and then figuring out the equation that has the variable that they want is already isolated and then they should plug in what they know.
    • With question #4 some students forget to add the solute and solvent together for the solution.
    • With the pH problems some students still need help with plugging the values into their calculators so they get help from me and their partners.