Answer:
it's a chemical change and an electrolytic reaction
The relation between density, mass and volume is

1) to calculate = volume
given:
Density = 0.0915 g/ mL
mass = 17.7 grams
formula used:

Thus
Volume 
Answer: 193.44 mL
2) the mass of sample will be

Answer: 7 g
It is harmful because you can get burned easy and your clothes can get dirty.