Question

26. Define a chemical reaction. What observation help you to determine whether a
chemical reaction has taken place.
27. How does the flow of acid rain water into the river make the survival of aquatic life in
the river difficult?​

Answer 1

Answer:

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Explanation:

There are several observations that can be made to determine if a chemical reaction has occurred. The first is a change in temperature. ... Another observation is the formation of a precipitate. This is a solid that forms out of solution. When a solute is dissolved in a solution, a chemical reaction took place.

2nd )

Answer: Acid rain water, if mixed with river water, lowers its pH below 5.6, i.e., makes river water acidic. But the living body works normally within a pH range of 7-7.8. That's why flow of acid rain water to river makes the survival of aquatic life in the river difficult.