Note that hay que emphasizes the precise action to be undertaken while carrying out a
process, while the third person plural of the verb simply explains what is done.42.1.2.2 Se+third person verb
23.9 (p. 111); 24.3 (p. 113)
A very frequent way of focusing on a process or procedure when the agent performing
the action is irrelevant is by using this expression with se followed by a verb in the third
person. The verb must agree in number, singular or plural, with the noun it refers to.
This construction is used in the spoken as well as the written language. In writing, it is
extremely common, especially where a formal style is required, as in describing a
laboratory experiment or a production process, giving a recipe, etc.
Se mezclan las dos sustancias en proporciones iguales en una
probeta, luego se calienta la mezcla...
The two substances are mixed in equal proportions in a test tube, then
the mixture is heated...Se cortan las verduras muy finas.
The vegetables are cut very finely.
Se deja remojando toda la noche.
You leave it soaking all night.Las mercancías se embalan y se trasladan en camiones hasta los
puertos de embarque, y desde allí se despachan a distintos países.
The goods are packed and sent by lorry to the embarkation ports, and
from there they are shipped to different countries.Note that the first three sentences describe the correct way to achieve a particular result,
so in this sense they are no different from a set of instructions you can follow. Here, the
agent performing the action is totally irrelevant. The last example, however, is
different, in as much as the process being described corresponds to a common practice
rather than steps to be followed. The agent here, although not mentioned, is
understood. As a general rule, you should not use this type of sentence when you need
to express the agent. Note also that where the agent is understood, as in the last
example, we could express the same idea more colloquially by using an impersonal
sentence such as the following:
Embalan las mercancías y las trasladan en camiones hasta los
puertos de embarque, y desde allí las despachan a distintos países.
They pack the goods and they send them by lorry to the embarkation
ports, and from there they ship them to different countries.If only a single action were expressed, as in ‘They are sent by lorry’, we would normally
use the impersonal third person plural, Las trasladan en camiones, and not the
construction with se.42.1.2.3 Ser+past participle
24.1 (p. 112)
A less frequent alternative in the expression of processes is this construction, known as
passive, in which ser, ‘to be’, is followed by a past participle which agrees in numberDescribing processes 42.1