Testing pH Indicators
VIDEO LINKS:
Consider before watching the videos:
How would you distinguish a clear acid solution from water?Lab Experiments (Write protocols based on the videos then complete your protocols as you perform experiments in class):
Data analysis and calculations (Use these if you need help with your data and calculations)
The pre-labs will be due before your lab class meets and will include Experimental Protocol, Chemical Table and Equipment Table.Experimental Protocol
(Analysis) Watch the experiment videos. Take notes on the protocols. Stop the videos and re-watch as necessary to acquire details of the procedure. Write out the protocol for each part of the experiment. (It can be written in sequential steps. Complete sentences are not necessary.) This is the protocol you follow, so be detailed.
Chemical Table
(Representation) Prepare your chemical table including the materials you use in the experiment. Here is a general template that you may use.
| Chemical Name | Chemical Formula | Molar Mass (g/mol) | Hazards | Reference | PPE |
| Sodium Chloride | NaCl | 58.5 | Skin irritation | https://fscimage.fishersci.com/msds/21105.htm | |
Equipment Table
(Analysis) Identify the equipment (type AND size) needed for the experiment and include the name and an image (picture) of each. Be sure to describe the equipment, how to use it, and why it is suitable for this use.
| Equipment Name | Equipment Picture or Description | Intended Purpose |
Data Collection
- (Acquiring competencies) Following your detailed protocol, perform all the experiments. Choose 3 indicators from those provided to fill out your personalized 6 indicators. Record your observations and take pictures of your key steps in the process. Your observations and images need to be incorporated in your data section and this section should be as detailed as possible as you will use this information to complete your data processing.
| pH of bufferà Indicator | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| Red cabbage | ||||||||
| Methyl red | ||||||||
| Phenolphthalein |
Data Processing
- (Existing knowledge, research, and views) Define acids and identify at least 2 characteristics.
- (Existing knowledge, research, and views) Define bases and identify at least 2 characteristics.
- (Existing knowledge, research, and views) Define what it means for a compound to be neutral.
- (Existing knowledge, research, and views) Define buffers in your own words.
- (Existing knowledge, research, and views) Identify the pH ranges for acidic, neutral, and basic solutions.
- (Existing knowledge, research, and views) Describe what an indicator does.
- (Existing knowledge, research, and views) Look up and report with a reference the pH or pH range where each indicator undergoes color change(s). (HINT: This could be a pasted chart, similar to the one included below from Schmiermund, T. pH Value; In The Chemistry Knowledge for Firefighters; Springer: Berlin, Heidelberg, 2023
- https://doi.org/10.1007/978-3-662-64423-2_14.
- (Representation) Create a table, identifying the pH or pH range where each indicator undergoes color change(s) according to your collected data.
- (Analysis) Identify the color of the solutions, if each indicator was separately added to a solution with a pH of 3.7.
- (Analysis) Comment on the consistency of the RGB values within your group.
- (Analysis) Identify any trends between color and values.
- (Analysis) Identify the color of the solutions, if each indicator was separately added to a solution with a pH of 8.5.
- (Analysis) Identify at least one of the 12 principles of green chemistry applied in this experiment. Justify your selection. 12 Principles of Green Chemistry
- (Assumptions and analysis) Fill in the following table using the observations and data from your experiments.
| Assumptions made | Testing the assumption | If assumptions are wrong ... |
| The pH of the buffer is unaffected by the indicator | Use a pH probe to measure the pH of each solution with and without indicator | |
| The RGB values of the same solution will be the same | ||
Summary
The summary has two parts: an abstract and an experimental protocol reflecting the experiment that you actually performed. The abstract and experimental protocol should both be between 100-250 words, size 12 Arial font each. There may be multiple experimental protocols for one experiment.Part 1.
Title of Experiment: Performed tasks and applied techniques to accomplish the goal of the experiment and a description of the system under study (the title you are given for the lab is insufficient). Ex. Comparative visual assessment of natural and synthetic pH indicator responses in buffered solutions of pH 3 to 10Abstract
(This is a highlight of what you learned from performing the experiment and processing your collected data. Below is a template and an example of what you are expected to write.)
In this lab experiment we investigated [purpose of your experiment] using [list the materials you worked with] and we found that [present the highlights of your results (include numbers)]. The results [present significant results]. The collected data compares to [draw conclusion about your results compared to other sources (this could be another group or the literature value)]. The [add type of measurement individually] measurement was collected using [describe instrument by sensitivity].
Think through this before writing:
- Purpose: What were you trying to do?
- Materials used: What chemicals and materials did you work with?
- Method: What instruments were used to collect measurements and how were the measurements collected?
- Results: What did you find out about the objects under study?
- Significance: What did you learn about the precision and accuracy of your techniques? How do your determined values compare to reported values?