A teacher put five grams of each of the four different substances into individual test tubes and then heated each test tube over a flame. The teacher asked the students to note the appearance of each
substance after heating. The results were as follows:
Reaction of Substances Table
Appearance Observations
Substance
Appearance
Before Heating While Heating After Cooling
Crackling,
black smoke
Black powder
Potassium
Purple
permanganate crystalline solid
Copper
Blue-green
carbonate
powder
Begins to
turn black
Black solid
Zinc oxide
White powder
Turns yellow
White powder
Sulfur
Yellow
crystalline solid
Yellow-brown Yellow-brown
liquid, smells liquid with large,
like rotten eggs fiber-like crystals
According to the data, which substance underwent a physical change?
A Potassium permanganate
B Copper carbonate
С Zinc oxide
D Sulfur