Nancy wants to find out how the steepness of a hill's slope affects the amount of soil that erodes from it. she has soil, a long pan, and a pile of books with which to build a model hillside. she has a watering can to model rainfall. in her experiment, which of the following factors should nancy make sure that she does not change?

the amount of water she pours on the model

Explanation:

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.

14,16 18 reacts with group