Which of the following is a sign a chemical reaction has occurred?
A blue liquid is mixed into a yellow liquid, and the mixture turns green.
A piece of metal is placed in water and produces sparks and gas.
Aliquid is heated on a hotplate, and bubbles form.
A solid powder is mixed into a liquid and disappears.

What amount of heat is exchanged when 106.2 grams of substance y goes from a liquid at 35 degrees celsius to a solid at the same temperature? melting point of substance y = 35 degrees c; δhvaporization = 3.67 j/mol; δhfusion = 3.30 j/mol. mwsubstance y = 28.22 g/mol. −12.4 j −3.51 x 102 j 1.24 x 101 j 351 j