We can find it using litmus papers.and when we eat some substances we feel like burning that's classified as acid and other is base

To determine whether a substance is an acid or a base experimentally, you can use various indicators or pH testing methods. Here are a few commonly used techniques:

1. pH paper or pH indicator solution: pH paper or indicator solution changes color depending on the acidity or alkalinity of a substance. Dip a strip of pH paper into the substance or add a few drops of indicator solution, and observe the color change. If the paper turns red or orange, the substance is likely acidic. If it turns blue or green, it is likely basic.

2. Litmus paper: Similar to pH paper, litmus paper also changes color based on the pH of a substance. Red litmus paper turns blue in the presence of a base, while blue litmus paper turns red in the presence of an acid. Dip the appropriate litmus paper into the substance and observe the color change.

3. Universal indicator: This is a pH indicator that provides a wide range of color changes across the entire pH scale. Add a few drops of universal indicator to the substance and observe the color change. Match the resulting color to the pH color chart to determine whether it is acidic or basic.

4. pH meter: A pH meter is a digital device that measures the hydrogen ion concentration in a substance. Dip the electrode of the pH meter into the substance and read the pH value displayed on the meter. pH values below 7 indicate acidity, while values above 7 indicate alkalinity.

Remember to handle all substances and equipment carefully and follow proper safety protocols while conducting experiments involving acids and bases.