Also, be careful. You've probably seen both "demasiado" and "tan" translated as "too." But in English, "too" as an adverb of degree can mean either "excessively" or just "very." The distinction here is that "tan" used that way is "very" (which can also be "so" in English) while "demasiado" is "excessively."
'Too' is an adverb, which can either mean 'also' (I'm coming too) or 'excessively' (too much).
'To' is a preposition which can mean 'towards', or 'until'. It also can mark indirect objects (I gave the ball to her) or infinitives (to run).
(for completeness) 'Two' is the number between 'one' and 'three', and is not interchangeable with either of the above
(see also, 'there' vs 'their' vs 'they're' for sound-alike words that native speakers sometimes struggle with).
Spanish has two verbs which can translate as "to be" (the fancy name for this is a copula): 'ser' and 'estar' ('es' and 'está', respectively). The 'ser vs estar' rules are one of the more difficult topics for English speakers (along with 'por vs para', 'preterite vs imperfect', or the subjunctive), but a good rule of thumb is the following:
'Ser' is usually used to describe more permanent qualities (it has the same Latin root as "essence"), such as personal traits, nationality, profession. 'Estar' is usually used to describe more temporary or changeable qualities (it has the same Latin root as "state") such as physical or emotional states, locations, or other temporary qualities.
In this prompt, the size of the spoon is essential to it's being, hence the use of "es" to describe it.
There are some common things that don't quite fit this rule, though. Dates and times use 'ser' (despite time seeming like a state), as well as the locations of events (not things); e.g., "La fiesta es a las siete. Es en mi casa. Mi casa está cerca de aquí." Going the other way, Spanish considers being alive or dead as a state (even though 'dead' isn't going to change), so you say "está muerto" and not "es muerto."
There are also some times when you can use either verb to express a nuance between permanent and temporary. For example, "ella es bonita" says that she is pretty, whereas "ella está bonita hoy" says she looks (particularly) pretty today -- maybe she is wearing a special dress or a new haircut or something. Some adjectives even change meaning depending on the choice of verb; "está lista" means "she is ready" whereas "es lista" means she is clever.
In this context, 'demasiado' is correct. - When used as an adverb (like here, where it modifies 'grande') the correct form is always 'demasiado'. - When used as an adjective (meaning 'too many' or 'too much'), it would agree in gender and number with the noun. E.g. 'demasiado pan', 'demasiada agua', 'demasiados libros' or 'demasiadas cucharas'.