When a noncount noun refers to all of its type or to a concept in general, it is not marked with an article.
The noun represents kindness in general; it does not represent a specific type of kindness.
The noun rice represents rice in general, not a specific type or a serving of rice.
In most cases, when you use a count noun to represent a general category, make the noun plural. Do not use unmarked singular count nouns to represent whole categories.
Fountains is a count noun that represents fountains in general.
In some cases, the is used with a singular noun that refers to a scientific class or category of items (most often animals, musical instruments, and inventions).
Exercises:
Using articles 1
Using articles 2
Using articles 3
Articles and types of nouns