Question

question 9. select the correct word that would complete the sentence to identify the type of change that occurs in each example. the formation of bubbles during a change is sometimes, but not always, an indication of a chemical change. for example, bubbles that form when water boils are an indication of a (select) change while bubbles formed when baking soda and vinegar are mixed are an indication of a (select) change.

Explanation:

When water boils, it changes from liquid to gas (water - vapor) but the chemical composition of water ($H_2O$) remains the same, which is a physical change. When baking - soda (sodium bicarbonate, $NaHCO_3$) and vinegar (acetic acid, $CH_3COOH$) are mixed, a chemical reaction occurs producing carbon - dioxide gas, water, and a salt, which is a chemical change.

Answer:

First blank: physical
Second blank: chemical