Test substances with Methyl orange and Phenolphthalein in ACIDS AND BASES – Class 7 Science Experiment
Chapter Name: ACIDS AND BASES
Activity Name: Test substances with Methyl orange and Phenolphthalein in ACIDS AND BASES
Activity Description:
In this experiment, we will test various substances using Phenolphthalein and Methyl orange solutions to determine whether they are acidic, basic, or neutral. Phenolphthalein is a pH indicator that changes color in the presence of a base, while Methyl orange changes color in the presence of an acid or a base.
Required Items:
- Table (3) with substances to be tested
- Phenolphthalein solution
- Methyl orange solution
- Test tubes
- Droppers
- Notebook for recording observations
- Table (7) to record the observations
Step by Step Procedure:
- Set up the work area with all the required items, including the substances from Table (3).
- Take a small amount of the first substance from Table (3) and place it in a test tube.
- Label the test tube with the name of the substance for easy identification.
- Add a few drops of Phenolphthalein solution to the test tube containing the substance.
- Observe any color change in the mixture. Note down the observation in Table (7) under the Phenolphthalein column.
- Clean the test tube thoroughly to avoid contamination and repeat steps 2-5 for the next substance from Table (3).
- Once you have tested all substances with Phenolphthalein, move on to the Methyl orange test.
- Take a new set of test tubes for the Methyl orange test to prevent any cross-contamination.
- Repeat steps 2-5, but this time use Methyl orange solution instead of Phenolphthalein.
- Note down the observations in Table (7) under the Methyl orange column.
- Repeat the process for all the substances listed in Table (3) one by one.
Experiment Observations:
Record your observations for each substance tested, noting the color changes observed with both Phenolphthalein and Methyl orange solutions.
Table (7) Example:
| Substance | Phenolphthalein Observation | Methyl Orange Observation |
|---|---|---|
| Substance 1 | Color change (or no change) | Color change (or no change) |
| Substance 2 | Color change (or no change) | Color change (or no change) |
| Substance 3 | Color change (or no change) | Color change (or no change) |
| … | … | … |
Precautions:
- Handle the substances with care, especially if they are known to be hazardous.
- Use a clean test tube for each substance to avoid contamination.
- Dispose of the substances properly after the experiment, following safety guidelines.
- Wash hands thoroughly after handling any chemicals.
- Take necessary precautions when using the droppers to prevent spillage or splashing of chemicals.
Lesson Learnt from Experiment:
The experiment helps us understand the acidic, basic, or neutral nature of different substances based on their reactions with Phenolphthalein and Methyl orange solutions. Phenolphthalein indicates the presence of bases, while Methyl orange indicates the presence of acids or bases.
This experiment reinforces the concept of pH indicators and how they can help identify the nature of a substance in terms of its acidity or basicity.
