An acid dissolved in water increases the concentration of

H+

Explanation:

AH + H2O --- A- + H+

Weak acids dissociate partially in the water while strong acids dissociate fully.  The pH of the solution will be determined by the number of H+ ions (protons) in the water. The pH is determined by; pH = -log[H+]

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

the major pests we deal with are insects, weeds and fungal diseases. a pesticide is a product, whether organic or chemical, used to kill the target pest. there are other techniques gardeners should use that can prevent the severe infestations that make the use of pesticides necessary