容量 and 量: capacity and the amount currently inside
Distinguish how much a bottle can hold from how much it currently contains. A capacity of 1 liter does not establish that the bottle is full.
容量 is how much can be held
容量, read ようりょう, means capacity here. この瓶は容量が一リットルで、家族の分のお茶が入る。 says that this bottle has a capacity of 1 liter and can hold tea for the family.
容量が一リットル states how much the bottle can hold. Distinguish it from a statement that exactly 1 liter of tea is currently inside.
量 is the amount used or present
量, read りょう, means amount. 料理に使う水の量を量った。 says that someone measured the amount of water to be used for cooking.
If a bottle with a capacity of 1 liter contains 300 milliliters of tea, the current amount of tea is 300 milliliters. Record the bottle’s capacity and its contents as different items.
What tells you whether it is full?
Capacity tells you how much the bottle can hold, but its current contents require separate information. Do not copy the capacity value into the actual 量 when only 容量 is given.
When describing the amount inside, identify what is present and how much there is. The same bottle can contain different amounts in different uses.
Must a bottle labeled 容量が一リットル currently contain 1 liter of tea?
Show the answer and why
No. One liter is its capacity. Check separate information for the current 量 of tea inside.