To model the total amount of water, \( w \), that Martina used in her science project, we can use the following equation:
\[ w = 8.5 \text{ ounces} \times 5 \text{ containers} \]
So the complete equation is:
\[ w = 8.5 \times 5 \]
This means Martina used a total of \( w \) ounces of water across the 5 containers.