Video Transcript
When using a balance to measure the
mass of a substance, the weigh boat is placed onto the balance and the balance is
tared. The best practice is to remove the
weigh boat before adding the substance and then return the weigh boat to the balance
pan. Why is this the case? (A) Because the mass would be
incorrectly measured if the weigh boat was left on the pan. (B) To check that the tare
operation has been performed correctly. (C) Because the substance may get
spilled on the balance. (D) To allow other people to use
the balance. Or (E) to save the batteries
powering the balance.
When we use a balance and a weigh
boat, it is because we want to know the accurate mass of the substance that we are
using for a reaction. The balance gets tared, which means
that it is set to zero with the mass of the boat on it. Any value that is recorded after
this point represents the mass of the substance that has been added.
However, when a substance is added
to a weigh boat, it is not unusual for some substance to be spilled. We are often not accurate with
transferring substances. If the substance is added with the
weigh boat still on the balance, then any spilled substance on the balance is being
weighed as well as any substance that made it into the weigh boat. This means you will not be able to
calculate accurately the amount of substance weighed out. You also have a messy balance to
clean up.
We should move the weigh boat off
the balance. This means that we do not spill any
substance on the balance. This ensures accuracy and improves
safety too.
So, the best practice is to remove
the weigh boat from the balance before adding the substance because the substance
may get spilled on the balance, or answer choice (C).
