Question

A science teacher wants to demonstrate a chemical change to her students. She fills a beaker with water and boils it on a hot plate. Eventually the volume of the water in the beaker decreases to a small amount.

What change(s) should the teacher make to the demonstration to correct her error?
(A) Use a different type of container.
(B) Use a different type of heating element.
(C) Use a different type of water.
(D) Use a different type of chemical.

Answer 1

The teacher should use a different type of chemical that undergoes a chemical reaction, as boiling water is a physical change, not a chemical change.

Step-by-step explanation:

To adequately demonstrate a chemical change to her students, the teacher should use a different type of chemical that undergoes a chemical reaction when heated rather than boiling water, which is a physical change. Boiling water only involves a phase change from liquid to gas (H₂O(l) → H₂O(g)), which is a physical change since no chemical bonds are broken or formed. An example of a chemical change could be the rusting of a nail (Fe + O₂ → Fe₂O₃), which involves new substances forming with different properties from the original materials. Compared to boiling water, rusting is accompanied by color changes, formation of new substances, and may involve temperature changes, all indicative of chemical reactions.