Name: ______KEY___________________Date_________________ Period_________
The Metric System: LAB ACTIVITY
Metric Measurement: MASS
Objective: In this activity, we will become familiar with the parts of a triple-beam balance. We
will practice measuring the mass of different objects. Following this, we will learn how to
“weigh-by-difference” to find the mass of different objects.
Procedures:
To Zero a Balance:
1. Check to make sure the balance is clean. Wipe and clean if necessary.
2. Move all weights to the left of the balance (next to the weight pan).
3. Look to see if the pointer line is perfectly in line with the mark on the post. If the lines
meets, this indicates that the scale is balanced.
4. If the lines do not meet, adjust the tare knob located underneath the weight pan. Turn the
knob toward you move the pointer down and turn the knob away from you to move the
poiner up. Move the knob by a half a turn at a time until the scale is balanced.
To Weigh Objects:
1. Make sure the balance is zeroed and the weight pan is clean.
2. Place and object on the weigh pan.
3. Move the weights on the beams until the scale is balanced. Start by moving the smallest
weight to the right. If it is too light to move the arm down, then move it back to the left
and then move the next larger weight. Do this until the arm remains below the line, then
slide the weight back to the left one time. The arm should move back above the line.
Then move the smaller weights until the same thing happens. (Make sure the two largerst
weights fall into the notches as you move them on the beams)
4. Weights can be measured as accurately as the nearest hundreth of a gram positioning the
smallest weight.
5. Once the weights have been positioned so that the beam pointer aligns with the mark on
the post, add each of the marked weights together to get a total. (Remember, the smallest
weight marks single grams, and the lines between the numbers on the beam mark tenths
of grams. The medium weight marks tens of grams, and the largest weight marks
hundreds of grams.
6. Record the total mass in the chart below under “Weight”. Be sure to include units each
time you record a number.
7. Once you are done measuring all objects, slide the weights back to the left and ensure the
scale pan is clean.
OBJECT
WEIGHT (In Grams) (Approximate Data)
iPad
Calculator
Green Resource Book
Die
487.54 g
102.40 g
508.47 g
5.60 g
Glue Stick
36.45 g
Weighting by Difference: (All data is SAMPLA DATA)
1. Place the gum, still in wrapper, on the triple-beam balance. Weigh and record.
___4.90_____ grams (gum in wrapper)
2. Remove the gum from wrapper, place the gum in mouth and begin chewing.
3. Place the wrapper back on the triple-beam balance. Weigh and record. Save the wrapper!
_____0.30____ grams (wrapper only)
4. Subtract the mass from Step 3 from the mass in Step 1. This is the mass of the Gum Only.
Record this mass in the “weight before” column on the following page.
5. Fill the 100 ml graduated cylinder with water to a level between 50 ml and 100 ml.
Record the volume of water.
___75.0_____ milliliters
6. Weigh the graduated cylinder and water. Record mass in “weight before” column.
7. Pour roughly half the water from the graduated cylinder into the sink. Record the new
volume of water ______35.0_____ milliliters. Re-weigh graduated cylinder and
water. Record mass in “weight after” column.
8. Fill the 250 ml beaker with water to a level between 150 ml and 250 ml. Estimate and
record volume ____250_________ milliliters. Weigh beaker and water. Record
mass in “weight before” column.
9. Pour roughly half of the water from the beaker into the sink. Estimate and record new
volume of water. ____125_________ milliliters. Re-weigh the beaker and
water. Record mass in “weigh after” column.
10. Remove gum from mouth. Place gum back in wrapper. Weigh the gum and wrapper.
_____1.65________ grams. Subtract the mass in Step 3 from this mass. This is the
mass of the gum after chewing. Record this mass in “weight after” column.
11. To find the amount of change for all objects, subtract the mass in the “weigh after”
column from the mass in the “weight before” column. Record this mass in the “weight
change” column.
OBJECT
100 ml graduated
cylinder
250 ml beaker
WEIGHT BEFORE
WEIGHT AFTER
WEIGHT CHANGE
115.65 g
80.90 g
34.75 g
271.15 g
125.86 g
145.29 g
Chewing Gum
4.60 g
1.35 g
3. 25 g
Questions:
1. Why is it important to make sure that the weigh pan is clean before weighing objects?
If the pan is dirty or there is material left on it from a previous measurement, the
mass that is measured would be greater than it should be.
2. Why do you think the mass of the gum changed?
The sugar that was in the gum has dissolved while I was chewing it. While there is
some saliva left in the gum, it still weighs much less due to the loss of the sugar in
the gum.
3. We determined how much the mass of the gum changed by comparing the mass before
chewing to the mass after chewing. Provide another example of how “weighting by
difference” could be used to figure out the mass of an object.
EXAMPLES:
- The mass of a bar of soap before and after
use.
- The mass of a pencil before and after
sharpening.
- The mass of a water bottle before and
after drinking.