Grade & Level: Grade 12 College, Chemistry and the Environment Unit

Description of the Antacid Inquiry (12 C)

In this inquiry, students are shown how to do a simple titration with basic apparatus, using a dropper instead of a burette.  This enables students to do several quick titrations using different antacids in a timely way. The teacher shows the students generally what to do and the students have to brainstorm

(initiate and plan) their own method, depending on which two antacids they choose.   Normally, in a titration, one tries to find the concentration of either the acid or the base.  In this case, the goal is to find out the concentration of the base and combine the effectiveness and cost together.  Students will make a recommendation about which antacid to buy.  Watch this helpful 1 minute instructional video:

  • Having trouble loading the video?  Copy and paste it into your browser directly.

Optional additional activities include: suggestions for acid/base demonstrations, M&M Solubility Skill Builder (variables) or Alka Seltzer Skill Builder, post-lab literacy piece.

Inquiry Focus:

Key Questions:  How do I compare two different antacids (effectiveness and price), using a fair test?

Do I understand how to change one variable and control others?  Do I know the difference between an independent and dependent variable?

Key Words: antacid, titrating, endpoint, equivalence point, acid, base, controlled variables, independent & dependent variables



Minimum time for this inquiry: 1.5 periods (0.5 period brainstorming, 1 full period for student inquiry)

Maximum time for this lesson series:3 periods

Period 1:

  • Skill Builder (variables) either M&M Inquiry (full period) or Alka-Seltzer Challenge (30-40 minutes) – optional

Period 2:

  • Demonstration – Milk of Magnesia (antacid that helps with stomach problems)
  • Literacy piece (30 min) & teacher demo/brainstorming  (20-30 min)

** Consider doing these two items (the demo or literacy piece) on separate days if you have many students who are ELL or struggle with literacy.

Period 3:

Inquiry day – full period

Big Ideas:

  • Relationships in chemical reactions can be described quantitatively.
  • Quantitative relationships of chemical reactions have applications in the home, workplace, and the environment.

Overall Expectations:

Scientific Investigative Skills

A1. Demonstrate scientific investigation skills (related to both inquiry and research) in the four areas of skills (initiating and planning, performing and recording, analysing and interpreting, and communicating).

 Chemistry and the Environment

F2. Investigate chemical reactions, using appropriate techniques of quantitative analysis.

Specific Expectations:

Strand A – Scientific Investigative Skills

A1.1 formulate scientific questions about observed relationships, ideas, problems, and/or issues, make predictions, and/or formulate hypotheses to focus inquiries or research;

A1.2 select appropriate instruments and materials (e.g. pH paper) for particular inquiries;

A1.3 identify and locate print, electronic, and human sources that are relevant to research questions; 

A1.5 conduct inquiries, controlling some variables, adapting or extending procedures as required, and using standard equipment and materials safely, accurately, and effectively, to collect observations and data;

A1.6 gather data from laboratory and other sources, and organize and record the data using appropriate formats, including tables, flow charts, graphs, and/or diagrams;

A1.8 analyse and interpret qualitative and/or quantitative data to determine whether the evidence supports or refutes the initial prediction or hypothesis, identifying possible sources of error, bias, or uncertainty;

A1.9 analyse the information gathered from research sources for reliability and bias;

A1.10 draw conclusions based on inquiry results and research findings, and justify their conclusions;

A1.11 communicate ideas, plans, procedures, results, and conclusions orally, in writing, and/or in electronic presentations, using appropriate language and a variety of formats (e.g., data tables, laboratory reports, presentations, debates, simulations, models);

A1.12 use appropriate numeric, symbolic, and graphic modes of representation, and appropriate units of measurement (e.g., SI and imperial units).

Chemistry and the Environment

F2.1 use appropriate terminology related to chemical analysis and chemistry in the environment, including, but not limited to: ozone, hard water, titration, pH, ppm, and ppb [C];

F2.2 write balanced chemical equations to represent the chemical reactions involved in the neutralization of acids and bases [AI, C];

F2.3 conduct an acid–base titration to determine the concentration of an acid or a base (e.g., the concentration of acetic acid in vinegar) [PR, AI].

Key Concepts: Acid-base neutralization, titration

Instructional Planning and Delivery:

Prior Skill Sets:

  • Understanding of variables (controlled, independent and dependent)
    •  Can use the M&M Solubility skill builder or Alka Seltzer skill builder

Prior Knowledge:

  • Knowledge of acids, bases and neutralization



    Watch this helpful 1 minute instructional video:

    * Having trouble accessing this video?  Copy and paste it directly into your browser


    Since the students are working with antacids and vinegar which are classified as consumables, they do not need to wear safety goggles.  However, teachers must ask students to wear them for consistency.  The indicator is still a weak acid.  Remind students that eating laboratory materials is prohibited.

    Materials and Equipment:

    • For the class:

    • electronic balance (2-3 per class) to measure the solid antacid tablets
    • weigh boats (1 per balance)



    Each pair of students would need:

    Erlenmeyer flask (2) – 250 ml funnel pHpH (phenolphthalein)indicator and pH paper mortar and pestle a pair of antacids (students could choose from solid & liquid antacids like Rolaids, Milk of Magnesia, Diovol, Gaviscon, TUMS, etc) with current prices graduated cylinder (50 or 100 mL) for measuring water vinegar graduated dropper (1 mL is a good size) – if you do not have droppers with markings, the students can calibrate their dropper by counting the number of drops contained within dropper a syringe with markings/graduations is a good option for liquid antacids or a 10 mL graduated cylinder distilled water

    Period 1 (optional but recommended):


    Minds On (10-15 min)

    Teacher Demonstration – Colour Changing Milk of Magnesia

    This demonstration (does not take a lot of materials) has the Milk of Magnesia solution (an antacid made of magnesium hydroxide) in a flask with universal indicator added.   A small amount of vinegar is added, which turns the solution acidic (red or yellow colour) and then as you swirl it, the acid and base react together and it turns back to basic (purple).  It is a great demonstration for the topic of acid/base and the students will be doing something similar.  The flask simulates how much acid and antacid can neutralize.  As you add more and more vinegar, there is a point where all the molecules of antacid (magnesium hydroxide) have been used up and neutralized and the solution will be a neutral green.  Students of all ages and levels absolutely love the dramatic colour changes!  The teacher can ask questions to draw out prior knowledge about indicators, acid/base neutralization reactions, colour changes and the pH scale concept.  Exact instructions can be found in the link below.


    Check out the video with Steve Spangler:


    Here is a detailed procedure of how to do it:


    Working Through It (30-45 min)

    If your students need to gain more concrete experience working with variables (identifying and manipulating them), try using documents BLM A - M&M Solubility (30 min) or BLM B - Alka-seltzer Challenge (45 min).  Both are fun and engaging activities for students ages 12-17. 


    Consolidate (10-15 min)

    Pull together ideas from the students about independent, dependent and controlled variables on the blackboard.  Some questions might include:  What did you change (independent variable)?  What did you measure (dependent variable)?  What are some factors that may lead to variations in your results (did you control your variables properly)?   If you were to repeat the activity, what could you do to obtain that would give more reliable results?


    Period 2:

    Minds On (5 minutes)

    Demonstrate the acid base titration (10 minutes) and complete the initiating and planning.


    Working Through It (20 minutes)

    Guide students through BLM C – Student Antacid Inquiry Worksheet (Parts A and B only).

    Demonstrate the acid-base titration (use the Adobe Sparks instructional video above to prepare, if needed).

    1. Take a solid antacid (Life brand or TUMS calcium carbonate) tablet and weigh it using an electronic balance. 
    2. Show students how you chose two antacids that are the same in all ways but one.  You are changing one variable (name brand vs. off brand).  Ask students some leading questions: Would it be okay if one of them was mint flavour and another lemon?  Check the expiry dates.  These should be similar and neither have expired.
    3. Ask a volunteer to use the mortar and pestle to crush the tablet into a powder.  Show students how to bend the weigh boat to get all of the powder into the Erlenmeyer flask.  Ask the volunteer to pour distilled water measured with a graduated cylinder into the flask and swirl to dissolve.  How much water should be used? (Answer: enough to dissolve the tablets).
    4. Add the pHpH indicator, which turns the solution pink. Add vinegar drop by drop with an eye dropper.  If you want to add a lot of vinegar, you can look at the mL graduation on the side of the eye dropper and add the vinegar one mL at a time.


    Note for the teacher: If you do not have a graduated eyedropper, you can show the students how to calibrate the unmarked dropper by marking the dropper (with a marker) at the top and halfway down.  Draw water up to a marked line and count the drops as the water comes out.  The students’ task is to identify the most effective antacid by determining which antacid can neutralize the most vinegar.  Students can do this either by measuring in millilitres or number of drops.


    Working Through It: Literacy Moment – Connecting to Health Issues (30 minutes)

    Have the students read the first five paragraphs of the article,   “Everything you ever wanted to know about indigestion (but were too bloated to ask)”.  Use BLM E: Antacid article questions (teacher answer key follows the student question worksheet).  This article talks about what antacids do as well as the difference between a heart attack and indigestion symptoms.


    Consolidation (10-15 minutes)

    Students complete worksheet for the Literacy Moment


    Period 3:  Inquiry Laboratory

    Full period devoted to inquiry – Parts C and D

    Student Support Resources:

    BLM C: Student Inquiry worksheet for Antacid Inquiry

    BLM E: Antacid article and questions (teacher answer key follows the student questions)

    Related Background Resources and/or Links:

    These are shown throughout this teacher resource.

    Assessment Opportunities:

    BLM A: M & M Skill Builder – can use the four question narrative report for students (rubric included in BLM D) – optional

    BLM C: Student Inquiry worksheet for Antacid Inquiry

    BLM E: Antacids Article Questions  – can be used for assessment as learning (A of L)

    Future Opportunities / Extensions:

    Other Possible Demonstrations:

    1. Cabbage Juice Chemistry – This is a short fun laboratory experiment that students may have already done in grade 10, but, it could be demonstrated with some added excitement using dry ice.  Dry ice can easily be purchased from such companies as Praxair. When dry ice is added to a cabbage juice solution it sublimates (goes from solid to gas) and dissolves into the water to create carbonic acid.  This changes the colour of the natural indicator. For more information, check out:


    1. Acid Breath – If you blow out through a straw into a basic solution with added pHpH, it turns colourless as it becomes acidic.  Steve Spangler also added some interesting solutions to the red cabbage solution. For more information, check out:


    3.  pH Rainbow Tube Demonstration – Flinn Scientific has a method to do this colourful demonstration (refer to link below). If you have never done this demonstration, it is worth learning because it can be used for grade 10 Science, 11U Chemistry and 12C Chemistry. For more information check out:


    1. Pop Rocks Demo – You could do this as a demonstration or show this short video.  Pop rocks are a pressurized carbon dioxide source.  When you place pop rocks into water (or in your mouth), they release gas and turn water acidic (carbonic acid formed). For more information, check out:

      Steve Spangler features a wide range of videos on his website.  He makes the demonstrations fun and includes modifications with safety mindedness.  In addition, step by step written procedures are available for each demonstration.