In this video explains Understanding the chemical properties of acids and bases: Let us see the experimental activity: Activity: Aim: To identify acids and bases using indicators and litmus paper.
Requirements: HCl, HNO3, Acetic acid, NaOH, Ca(OH)2 caicium hydroxide, Watch-Glass, Ammonium hydroxide.
Take 2 – 3 drops of solution on two watch-glasses from the samples like HCl, HNO3, CH3COOH, NaOH, Ca(OH)2 and NH4OH.
Step 1: Test with indicator i.e., with a drop of the methyl orange indicator and phenolphthalein Observe the color of the solution?
Here we can observe the color change in one watch glass containing acid added with methyl orange indicator which is red in color and the other watch glass containing acid when added with a drop of phenolphthalein indicator which is colorless after addition. Similarly watch-glass containing bases give pink color with phenolphthalein and yellow color with methyl orange indicator.
Thus we can identify the chemical property of a substance by the change in color of the indicator
Step 2: Test with blue litmus paper? Put the blue litmus paper on the watch-glass and observe the color of the litmus paper? If blue litmus is changed to red that is called Acid. If red litmus is changed to blue that solution is base. Finally from these indicators tell whether a substance is acid or basic by observing change in color. Some substances whose odour changes in acidic or basic media are called factory indicators.

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