Chemical changes Transitional Reasoning Download PDF

Questions

1. 1.

   During a laboratory investigation, a student adds dilute hydrochloric acid to solid calcium carbonate in a sealed syringe, observing rapid bubbling, the dissolution of the solid, and an outward movement of the plunger as gas accumulates. In a separate trial, the student gently warms carbonated water in an identical syringe, observing gas bubbles forming and pushing the plunger outward as well. Which analysis correctly identifies the evidence demonstrating that a chemical change occurred in the first trial but not in the second?

   • A) In both trials, gas bubbles formed, which confirms that chemical bonds were broken and rearranged to produce new substances in both systems.
   • B) The first trial is a chemical change solely because solid matter disappeared, whereas the liquid in the second trial remained completely visible.
   • C) The first trial produced a gas through the rearrangement of atoms into chemically new substances, whereas the second trial merely released dissolved gas molecules without changing their chemical identity.
   • D) The second trial is a chemical change because heat was supplied to release the gas, whereas the first trial proceeded without external thermal energy.