How do I know when to use "estar" versus "ser" for the verb "to be"?
The verb "estar" is used for changeable conditions and states of being such as location, mood, appearance, and feelings. If you can change the condition fairly easily, such as by moving to a new location or taking a nap, then you know it is temporary and "estar" is the correct verb to use. "Estar" is also used in the present progressive tense, such as "Estoy comiendo," which means "I am eating." If you can successfully insert "right now" as an invisible clause, such as "(right now) I am in front of my computer," you know "estar" is the right verb to use. "Ser" is used for more permanent conditions of identity such as nationality, race, gender, profession, physical characteristics like height or weight, or what something is made of. It is also used for time conditions considered unchangeable such as the days of the week (Hoy es lunes). "Ser" is used to describe the more fixed aspects of personality, such as kindness or intelligence. Sometimes using "estar" versus "ser" can greatly change the meaning of a sentence. For example if you say, "Estoy aburrida," the meaning is that I am (temporarily, right now) bored. However, if you say, "Él es aburrido," you are saying "He is a boring person," suggesting it is a permanent personality characteristic.
How do I know if I should use "who" or "whom" in a question or in a sentence?
The easiest way to choose the right word in a question is to check if it can be answered using an indirect object such as "him," "her," or "them." For example, if the answer is, "I am speaking to them," then the correct phrasing of the question would be, "To whom are you speaking?" In a sentence, when the unknown person is the indirect object, you use "whom," such as, "I did not know with whom I was speaking when I called." A second and less common case is using "whom" as a direct object, without a preposition (such as "to," "from," "at," or "with") preceding it. As a question, you can still use the technique of replacing the answer with a pronoun such as "him," "her," or "them," as in, "Whom are you calling?" "I am calling them." "Who" is only used as a subject, where it would replace the words "he," "she," "they," or a person's name in the main action. So for example, if the answer may be "John thew the ball," the question would be correctly phrased as, "Who threw the ball through this window?" As a sentence, "who" is again used as a subject, such as, "I know who threw the ball."
What is fresco, and how does it differ from oil painting?
Fresco is a painting technique typically used on walls and ceilings, where a mixture of pigments and water are applied to a prepared wet plaster layer. As this layer dries, the colors are chemically bound with the lime mortar to become physically part of the wall, not just sitting on the surface. In true fresco, only certain pigments can be used, as they must be chemically compatible with the alkaline plaster, whereas in oil painting, any pigment that can be mixed with a linseed oil binder may be applied. Oil paint is typically applied to a prepared canvas, wood, or sometimes metal surface, and it may be applied in multiple layers over time to achieve various techniques and surface qualities. By contrast, fresco can only be worked in the time it takes for the mortar to dry, called a giornata, or "day's work" in Italian.