It’s a long established fact that acid rain can do significant damage to trees, plants, wildlife, architecture, and monuments. Leaves, fruits, and flowers of trees and plants that are affected by acid rain wither and die eventually, together with the rest of the trees and plants they’re attached to. Fish and certain land animals, like frogs, will have a difficult time thriving and reproducing in acidic habitats, and when this happens in an area, the food chain present in the place is eventually disrupted. Acidic particles cause the corrosion of metals and the rapid deterioration of both stone and paint.
Unfortunately, observation (using the senses) is not enough to determine the acidity of rain so it does not end up brought to taps and shower heads by pumps for tanks in your respective homes.

Determining the acidity of rain

There are numerous ways to determine rain acidity, with the most effective method being the direct measure of its pH. Rain with a pH of lower than 7 is acidic, while rain with a pH above 7 is basic.

To measure pH of rain, one needs litmus paper, which is a type of paper that changes colour according to the pH level of a substance. Once you have litmus paper, you should then get a small, well-washed plastic container. This container you will leave under the rain until it is filled with a good amount of rainwater.

Once the container has been filled with a good amount of water, take it indoors, then do the litmus test. Dip a part of the litmus paper in the water. The colour of the litmus paper should change instantly. Refer to the chart that comes with the sheets of litmus paper you purchased to know what pH the colour stands for.
Another way to determine rain acidity is by measuring the hydrogen ion concentration in your sample of water. Hydrogen ions form when acidic substances are dissolved in water.
To measure hydrogen ion concentration, a popular method involves the use of acid-base indicators. These are substances which change colour depending on hydrogen ion concentration. Some of these acid-base indicators are natural, plant-based products, with one example being black tea. Add lemon juice (an acid) to it, and the black tea should go from black to light brown, a sign of high hydrogen ion concentration in the juice.
The use of a pH-meter is another great way to measure hydrogen ion concentration, as it is more accurate (not to mention that it reads pH too). The instrument features a 0-14 pH scale. The smaller the number in the reading, the higher the hydrogen ion concentration. The higher the hydrogen ion concentration, the more acidic the substance.
Normal rain pH

Pure tap water has a 7 pH (neutral) and unpolluted rainwater has a pH somewhere between 5.5 and 6 (acidic). Rain is normally a little acidic since carbon dioxide dissolves on it. Truly acidic rain, on the other hand, has a pH 5 or lower, brought about by the more acidic substances dissolved there. Some samples that have a pH somewhere on or near 4 were gathered in places that have polluted soil and so many withered plants and trees.