Learn Polish: Chcę dużą kawę mrożoną. - I want a large iced coffee.

This is a great example of Polish word order rules. The word dużą (large) is a descriptive adjective that gives us an opinion or temporary trait like size, so it goes before the noun. The word mrożoną (iced) is a classifying adjective that tells us the specific type or permanent category of coffee, so it goes after the noun.

Why do these words end in ą and ę instead of a?

The verb chcę (I want) requires its direct object to be in the Accusative case. The dictionary phrase is duża kawa mrożona. In the Accusative case, the feminine noun kawa changes its ending to ę (kawę), while the feminine adjectives change their endings to ą (dużą, mrożoną).

I learned that chcę sometimes takes the Genitive case. Why is it Accusative here?

You can use both with food and drinks, but they have a slightly different feel. Using the Genitive (chcę dużej kawy) sounds like you want some coffee, treating it as an uncountable liquid. Using the Accusative (chcę dużą kawę) treats the coffee as a single, countable item, like ordering one specific cup at a cafe.

Does mrożona strictly mean iced?