Name:__________________________________________Period:_______________Date:________________
Lab Mass in Chemistry
Purpose: Learn to measure mass using the triple beam (tri beam) balance
Background: It is important to be able to mix the correct amount of each substance together in a mixture. Measured
mass allowed us to communicate and to describe the exact quantity needed. In this lab we are going to practice the
correct technique on how to weight substances using a triple beam balance.
Materials:
Triple beam balance
Electronic balance
Vial
Tap water
Oil
Pipette
Detergent (soap)
Pre-Lab Questions:
1. What do we use a balance for? _____________________________________________________________________
2. Why is it important to obtain the exact weight of a substance?_____________________________________________
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Part 1: Using the triple beam balance
1. Leave your triple beam balance on a flat surface. Move all the weight to the left hand side and make sure that it levels
out and the white marks at the end lined up
2. Pick any 3 objects (use adjectives to describe the three objects), measure the mass of the given objects and record in
grams.
Object
Description
Mass (g)
1
2
3
3. Bring the three objects to the front and double check the weight using the electronic balance. Put a check mark next
to your mass if it’s the same as the electronic balance. If not then put a comma after the old mass and write the new one
next to it.
Part 2: Obtaining exact mass
1. Put the vial and the cap on the balance. Record the mass of both here _________________
2. Find a way to add exactly 10.0 grams of tap water from the sink into your vial
a. Describe what you did to get exactly 10.0 grams of water in the vial?
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c. Remove the vial from the balance (keep the water). Did the balance go back to zero? Why or why not?
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Part 3: Adding more mass
1. Find a way to add exactly 1.0 gram of oil into the same vial containing the water. You were able to remove or add
more water as needed in part 2 to get 10 grams of water. However, removing oil after you added it into water will be
tricky.
2. Observe these two substances
a. Write down a 2-3 sentence procedure that would allow you to accurately add exactly 1.0 gram of oil to the same vial.
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b. Follow your procedure and use the pipette to add the oil. Clean up any spills using paper towel.
c. Draw and label your vial of how the oil and water behave when they’re together 
Part 4: The function of soap
1. Add 15 drops of liquid detergent to the same vial containing the oil and water then recap it
2. How much mass increased? [Mass of added detergent (g)________________________]
3. Observe how the appearance of the detergent
3. Gently shake the vial for a few minutes
a. Describe the behavior of the oil and water mixture before and after you added the detergent
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b. Generally, what do we use soap for?
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c. Propose and explanation for how detergent works.
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d. What do you think will happen to your vial if we add more detergent to it?
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Clean up procedure:
Use detergent to clean your vial, make sure all the oil have been removed. Safe to go down the drain.