To model the total amount of water, \( w \), that Martina used, you can use the following equation:
\[ w = \text{number of containers} \times \text{amount of water per container} \]
In this case, Martina has 5 containers and each container has 8.5 ounces of water. Therefore, the equation would be:
\[ w = 5 \times 8.5 \]
Calculating that gives:
\[ w = 42.5 \text{ ounces} \]
So the complete equation that models the total amount of water is:
\[ w = 5 \times 8.5 \]