Silicon dioxide powder dissolves in water. Is this a physical or a chemical change?

Fugu, also known as puffer fish, is a sushi delicacy that can also be lethal. puffer fish contain a powerful toxin that can kill an adult a few hours after ingestion. sushi chefs who prepare fugu must be specially trained because any contamination of the toxin-free areas of the fish can be deadly. recently this toxin has been put to good use, as scientists have discovered that a purified form of it can treat severe pain in cancer patients. this recent scientific discovery would fall under which area of chemistry? applied biochemistry pure organic chemistry pure physical chemistry applied inorganic chemistry

Can someone me with questions 12 and 13 plz.

Choose all the answers that apply. ionic compounds dissolve easily in water do not dissolve in water have low melting points have high melting points conduct electricity when melted