Learn Portuguese (Portugal): Aquilo é idêntico!

While o mesmo means the same, idêntico is a strong adjective meaning identical or exactly alike. You could say Aquilo é o mesmo to mean That is the same, but idêntico emphasizes that the features of the object are completely identical to something else.

Why use aquilo instead of aquele or isso for that?

Aquilo is an invariable demonstrative pronoun used for an abstract idea or a thing whose name hasn't been mentioned, located far from both the speaker and the listener. If you were pointing at a specific masculine noun, you would use aquele. Isso is used for things close to the listener.

Since aquilo is invariable and doesn't have a gender, why does idêntico end in an -o?

In Portuguese, when an adjective describes an invariable, gender-neutral pronoun like aquilo, isto, or isso, the adjective defaults to the masculine singular form. That is why we use idêntico rather than idêntica.

Why do we use é from the verb ser rather than está from the verb estar?