How many significant figures are present in the following number:
0.0001790497

According to significant figures we have leading zeros, trapped zeros and zeros at the beginning. So that number is a leading zeros and its has 7 SGF.

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.