Hey, no idea if you still want an answer. It is a chemical change! The Cobalt (II) Chloride, CoCl2, exists as different forms of hydrates. Essentially, how much water is interacting with CoCl2. As you heat it, the water boils off reducing the hydration factor until it is completely dry (bright blue at the end). The amount of water interacting with CoCl2 determines the colour. The reason why water changes the colour of CoCl2 is more complicated, but I would be happy to explain if you like!
is this a physical or chemical change?
Hey, no idea if you still want an answer. It is a chemical change! The Cobalt (II) Chloride, CoCl2, exists as different forms of hydrates. Essentially, how much water is interacting with CoCl2. As you heat it, the water boils off reducing the hydration factor until it is completely dry (bright blue at the end). The amount of water interacting with CoCl2 determines the colour. The reason why water changes the colour of CoCl2 is more complicated, but I would be happy to explain if you like!