# Question Video: Identifying Why It Is Best Not to Add the Substance Being Weighed to the Weigh Boat While the Weigh Boat Is on the Balance Chemistry

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 [E] To save the batteries powering the balance

01:51

### 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).