Question

3.) what are the fizzy bubbles made out of that show up when you toss a bath bomb into a water-filled bathtub?

Explanation:

Bath bombs typically contain ingredients like sodium bicarbonate (baking soda) and citric acid. When a bath bomb is added to water, these two substances react chemically: $NaHCO_3 + H_3C_6H_5O_7
ightarrow Na_3C_6H_5O_7 + H_2O + CO_2 \uparrow$. The fizzy bubbles are the carbon dioxide ($CO_2$) gas produced from this acid - base reaction.

Answer:

The fizzy bubbles are made of carbon dioxide ($\boldsymbol{CO_2}$) gas, which is produced by the chemical reaction between ingredients (like sodium bicarbonate and citric acid) in the bath bomb when it is added to water.