Grade 7 | Science | Indicators- Natural and Olfactory Indicators, Acids, bases and salts, Olympiad, CBSE, ICSE, SOF, ITO
What are Indicators?
There are some substances which help us to detect whether a substance is acidic or basic in nature. Such substances are known as indicators.
There are some naturally occurring indicators which change their original color when they come in contact with acidic, basic and neutral substances.
This is the most common natural indicator which is available in almost every home. It contains a substance called curcumin which gives it a beautiful yellow color.
A basic substance will change a yellow colored stain on a cloth of the turmeric into brownish red and an acidic substance will reverse this brownish red stain back into its original yellow color.
But a neutral substance like water will not change the yellow color of turmeric stain.
The petals of China rose are used to make a solution with water which is pinks in color and is a good natural indicator. With the acidic solution, it gives dark pink (magenta) and with a basic solution, it yields green color. With a neutral medium, it remains as it is with no change in color.
Litmus is a natural dye which is extracted from lichens. In neutral water, its color is mauve (purple). In acidic solution, it gives a red color while in basic solution, it yields a blue color.
Some natural substances change their odor when they come in contact with the acidic or basic medium. Like Onion, Vanilla, and Clove oil are some common olfactory indicators.
In bases, such indicators give different odor than the original one while in acids the odor remains the same.