Hannah does an experiment. She has two colorless chemicals that she mixes together in a beaker. Which of the following indicates that a chemical change occurs when she mixes the two chemicals together?

Question

I. The chemicals change color from colorless to purple.
II. A yellow gas forms.
III. A brown solid forms in the bottom of the beaker.
IV. The temperature of the chemicals rises 15°C.
A.
I and III only
B.
I, II, and III only
C.
I, II, III, and IV
D.
II and III only

Answer 1

To determine which observations indicate that a chemical change occurs, we can consider the following:

1. Color Change (I): The chemicals change color from colorless to purple, indicating a chemical reaction may have taken place.
2. Gas Formation (II): The formation of a yellow gas suggests a new substance is produced from the reaction, indicating a chemical change.
3. Solid Formation (III): The appearance of a brown solid (precipitate) indicates that a new substance has formed, signifying a chemical change.
4. Temperature Change (IV): A rise in temperature can imply that a chemical reaction is exothermic, leading to the production of new substances.

Since all of these observations (I, II, III, IV) can indicate a chemical change has occurred, the correct answer would be:

C. I, II, III, and IV