Concentrated chemicals should be __________ into water.

The correct answer highlights the important safety practice of handling concentrated chemicals. When dealing with concentrated chemicals, they should always be diluted into water rather than adding water to the chemicals. This approach minimizes the risk of reactions that can cause splashes, spills, or hazardous fumes.

By diluting concentrated chemicals into water, you create a controlled environment where the chemical can safely dissolve, reducing the chances of an exothermic reaction, which may release heat and create dangerous conditions. This practice is particularly crucial in carpet cleaning, where improper handling can lead to damage to carpets or harm to the user.

The other options suggest methods or practices that do not align with safe chemical handling protocols. Mixing or heating, for instance, can introduce additional risks, while separating or discarding does not address the proper method for using concentrated solutions. Storing or eliminating are unrelated to the immediate act of preparing a cleaning solution.

Thus, the emphasis on diluting or pouring concentrated chemicals into water is a foundational safety principle within the context of carpet cleaning and chemical handling.