Question

1. a student places a piece of zinc metal into a beaker of hydrochloric acid and records the following observations:

observation	evidence collected
2	the beaker becomes warmer over time
3	the metal gradually disappears
4	the liquid looks the same as before, just with fewer bubbles

based on the data, which students conclusion is best supported by the students observations?

a physical change occurred because the appearance of the liquid did not change.

a chemical change occurred because zinc mixed evenly into the hydrochloric acid without forming anything new.

a chemical change occurred because new substances formed and there was a change in thermal energy.

a physical change occurred because the zinc only changed size and shape.

Explanation:

A chemical change occurs when new substances are formed and there is a change in thermal energy. Bubbles forming (gas production), the beaker warming (heat - energy change), and the metal disappearing (reacting to form new substances) are all signs of a chemical reaction.

Answer:

A chemical change occurred because new substances formed and there was a change in thermal energy.