Classification of substances in ACIDS AND BASES – Class 7 Science Experiment

Chapter Name: ACIDS AND BASES

Activity Name: Classification of substances in ACIDS AND BASES

Activity Description:

In this experiment, we will classify different substances into three categories: acidic, basic, and neutral. This classification will be based on the observations made during the experiment.

Required Items:

1. Various substances to test (e.g., lemon juice, vinegar, baking soda, soap, water, etc.)
2. Water
3. pH paper or pH indicator solution
4. Test tubes or small containers
5. Droppers or pipettes

Step by Step Procedure:

1. Take small test tubes or containers and label them as A, B, C, and so on, depending on the number of substances you want to test.
2. Add a small amount of each substance you wish to test into separate test tubes or containers. If the substance is in solid form, dissolve it in a small amount of water.
3. Take a piece of pH paper or use a dropper/pipette to add a few drops of pH indicator solution to each test tube containing the substances.
4. Observe any color change in the pH indicator or pH paper for each substance. The pH paper will change its color according to the acidity or basicity of the substance.
5. Compare the color change with the pH scale to determine the approximate pH value of each substance.

Experiment Observations:

Record the color changes observed for each substance after adding the pH indicator or pH paper. Also, note down the pH range associated with the colors observed on the pH scale.

Precautions:

1. Use appropriate safety measures while handling chemicals and substances. Wear gloves and safety goggles to protect your hands and eyes.
2. Avoid direct contact with chemicals, especially strong acids and bases.
3. Dispose of the used substances properly according to your school or local guidelines.

Lesson Learnt from Experiment:

Based on the color changes observed with the pH indicator, substances can be classified into the following categories:

Acidic Substance: Substances that show a color change indicating a pH value below 7 are acidic. Examples include lemon juice and vinegar.

Basic Substance: Substances that show a color change indicating a pH value above 7 are basic (alkaline). An example is baking soda or soap solution.

Neutral Substance: Substances that show no significant color change and remain close to the pH value of 7 are considered neutral. Water is a typical example of a neutral substance.

This experiment helps us understand the basic properties of acids, bases, and neutral substances and their pH levels. It also demonstrates how pH indicators can be used to classify substances based on their acidic or basic nature.