Learn Finnish: Tislaamossa hiiva lisätään tuhanteen kiloon mallasta. - In the distillery, the yeast is added to a thousand kilos of malt.

This is the rule for measure phrases. The unit (kilo) and its number (tuhat) take the case required by the verb. Here, it is the illative case (tuhanteen kiloon) because of the verb lisätä (to add into). The substance being measured acts as an uninflected partitive modifier and stays locked in the partitive case (mallasta) regardless of the main noun's case.

Why do we say tuhanteen kiloon instead of using the partitive for the noun after the number?

When a number phrase is the subject or object, the following noun takes the partitive singular (like tuhat kiloa). But when the phrase requires a local case like the illative here ('into'), both the number and the noun must agree and inflect into that same case. Thus, both tuhat and kilo take the illative endings.

Since hiiva (yeast) is the object being added, why isn't it in an object case like the accusative?

In standard Finnish, the total object of a passive verb (lisätään) is always in the nominative case rather than the genitive-looking accusative. Since the yeast is being added in its entirety in this context, it takes the nominative form hiiva.

How is the word tislaamossa (in the distillery) formed?