Final answer:
When red litmus paper turns blue, this indicates that the substance is basic (alkaline), as bases increase the pH level which causes the red litmus paper to change color.option C is correct answer.
Step-by-step explanation:
If red litmus paper turns blue, it indicates that the substance is basic (alkaline). Litmus paper is a type of pH paper that changes color in the presence of an acid or a base. The color change in litmus paper happens because it is treated with a natural water-soluble dye that reacts differently to the pH level of the substance being tested.
When red litmus paper is introduced to a basic substance, the increased pH causes the red litmus paper to turn blue, confirming that the substance has basic properties.
Bases feel slippery or soapy and do not react with metals in the way that acids do. When a base is neutralized by an acid, they react to produce a salt and water. Another indicator, phenolphthalein, also changes color in the presence of a base—it turns pink from its colorless acidic form. Common household examples of bases include soap, toothpaste, bleach, and cleaning agents.
Therefore, the correct answer to the question of what it indicates if red litmus paper turns blue is: C) The substance is basic (alkaline).