# The Centigram Balance: Direct Weighing

Topics: Mass, Weight, Kilogram Pages: 5 (1257 words) Published: February 15, 2012
Procedure:

The Centigram Balance:
Direct Weighing
1. Weigh a slug on a centigram balance using the direct-weighing technique: Obtain a centigram balance from the Balances option under the Equipment menu. Select the centigram balance and add one slug from the Chemicals dialog box. Record the slug mass in the Observations.

2. Weigh the same slug directly on another centigram balance: Obtain a second centigram balance from the Balances option under the Equipment menu and place it under the first centigram balance such that the pans line up under each other. Select the centigram balance with the slug and choose Pour/Decant from the Procedures menu. Record the mass of the slug.

Weighing by Difference
1. Weigh the same slug by difference:
Determine the mass of an empty 100-ml beaker by obtaining a 100-ml beaker and placing it on the pan of the empty centigram balance. Record the mass of the beaker.
Move the beaker below the pan of the centigram balance that contains the slug. Select the centigram balance and choose Pour/Decant from the Procedures menu. Place the beaker with the slug on the pan of the centigram balance used to weigh the beaker. Record the mass of the beaker and slug.

Calculate and record the mass of the slug.
2. Use the other centigram balance to determine the slug mass by difference: To store the slug, remove the beaker with slug and position it over the pan of the same centigram balance, select the beaker and choose Pour/Decant from the Procedures menu. Place the empty beaker on the pan of the other centigram balance. Record the mass of the beaker.

Move the beaker below the pan of the centigram balance that contains the slug. Select the centigram balance and choose Pour/Decant from the Procedures menu. Place the beaker with the slug on the pan of the centigram balance just used to weigh the beaker. Record the mass of the beaker and slug.

Calculate and record the mass of the slug.
Move the beaker and slug to the side for use with the electronic balance. 3. Weigh an unknown mass on a centigram balance using the direct-weighing technique: Select a centigram balance and add an unknown mass from the Chemicals dialog box. Record the identification number.

Record the mass of the unknown by direct weighing.
4. Weigh the same mass by difference:
Determine the mass of an empty 100-ml beaker by obtaining a 100-ml beaker and placing it on the pan of the empty centigram balance. Record the mass of the beaker.
Move the beaker below the pan of the centigram balance that contains the mass. Select the centigram balance and choose Pour/Decant from the Procedures menu. Place the beaker with the mass on the pan of the centigram balance used to weigh the beaker. Record the mass of the beaker and the unknown.

Calculate and record the mass of the unknown.
Delete one of centigram balances and move the beaker with the unknown mass to the side for use with the electronic balance.

The Electronic Balance:
Mass of the Slug by Direct Weighing and by Difference
Determine the mass of the same slug used above by direct weighing and by difference using either the Electronic Balance or the High Sensitivity Balance. 1. Direct weighing:
Select the beaker with the slug and choose Transfer to New Container from the Procedures menu. Select an electronic or high sensitivity balance from the Transfer Contents dialog box. Record the mass of the slug using the number of figures justified by the sensitivity of the balance. 2. By Difference:

Select the balance with the slug and choose Transfer to New Container from the Procedures menu. Select a 100-ml beaker from the Transfer Contents dialog box. Select the beaker with the slug and place it on the balance. Record the mass of the beaker and the slug.

Remove the beaker from the balance.
Select the beaker and choose Empty from the Procedures menu. Place the empty beaker on the balance.
Record the mass of the beaker.
Calculate and record the mass of the slug.

Mass of the...