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? 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. ii and iii only b. i, ii, iii, and iv c. i and iii only d. i, ii, and iii only