To model the total amount of water (w) that Martina used in her science project, you can use the equation based on the number of containers (5) and the amount of water in each container (8.5 ounces).
The equation would be:
\[ w = 5 \times 8.5 \]
This represents the total amount of water used, where 5 is the number of containers and 8.5 is the amount of water in each container.
So, completed, the equation is:
\[ w = 5 \times 8.5 \]