ACTIVITY OF WET LABS MEASURING THE MASS & VOLUME OF OBJECTS AND SUBSTANCES
A. The mass of the solid object
Choose a Solid Object whose mass you will measure and describe the Solid Object in the appropriate location on the Data sheet.
Choose a container to use for determining the mass of the Solid Object; this will be Container A. Describe the type of container used in the appropriate location on the Data sheet.
Place Container A on the balance, then record the Mass of Container A on the Data sheet to the nearest 0.1 g.
Place the Solid Object into Container A, then record the Mass of Container A and the Solid Object to the nearest 0.1 g.
Determine the Mass of the Solid Object by subtracting the Mass of Container A from the Mass of Container A and the Solid Object. Record the value on the Data sheet.
Remove Container A and the Solid Object from the balance, then repeat Steps A3-A5 two more times for a total of 3 trials.
After performing 3 trials, calculate the average value.
Now place Container A on the balance and push the tare or zero button.
Place the Solid Object into Container A, take a picture to upload with your report, then record the mass to the nearest 0.1 g to determine Mass of the Solid Object without using the difference method. Record this mass on your Data sheet.
B. The Mass of a Granular Solid
Choose a Granular Solid whose mass you will measure and describe the Granular Solid in the appropriate location on the Data sheet.
Choose a container to use for determining the mass of the Granular Solid; this will be Container B. Describe the type of container used in the appropriate location on the Data sheet.
Place Container B on the balance, then record the Mass of Container B on the Data sheet to the nearest 0.1 g.
Measure out either ¼ cup (2 fluid ounces) or 50 milliliters of Granular Solid using the measuring cup and place it into Container B, then record the Mass of Container B and the Granular Solid to the nearest 0.1 g. Indicate whether you used ¼ cup or 50 mL and take a picture to upload with your report.
Determine the Mass of the Granular Solid by subtracting the Mass of Container B from the Mass of Container B and the Granular Solid. Record the value on the Data sheet.
Remove Container A and the Granular Solid from the balance, then repeat Steps B3-B5 two more times for a total of 3 trials.
After performing 3 trials, calculate the average value.
C. The Mass of a Liquid
Choose a container to use for determining the mass of water; this will be Container C.
Describe the type of container used in the appropriate location on the Data sheet.
Place Container C on the balance, then record the Mass of Container C on the Data sheet to the nearest 0.1 g.
Measure out either 1 cup (8 fluid ounces) or 250 milliliters of water using the measuring cup and place the water into Container B, then record the Mass of
Container C and Water to the nearest 0.1 g. Take a picture to upload with your report.
Determine the Mass of Water by subtracting the Mass of Container C from the Mass of Container C and Water. Record the value on the Data sheet.
Remove Container A and the Water from the balance and pour out the water. Dry Container C, then repeat Steps C3-C5 two more times for a total of 3 trials.
After performing 3 trials, calculate the average value.
Pre-Laboratory Questions
Describe how to use the “difference method” when performing mass determinations. Why are masses in the chemistry laboratory usually determined by the difference method (using a beaker to contain the object to be weighted, rather than just placing the object directly on the pan of the balance)?
Why should the mass of an object never be determined while the object’s temperature is above room temperature?
If you weigh a hot object on the balance, the reading will be higher, the same, or lower than if it had been weighed after it cools to room temperature?
Why should liquids never be poured on or near the balance?
Pre-Laboratory Questions
What is a meniscus? Sketch a 10 mL graduated cylinder filled to a volume of 5.24 Ml.
How do we typically read the liquid level when dealing with a liquid that forms a meniscus? Describe how to read a volume using a graduated cylinder with graduation marks every 1 mL.
Why is a rubber safety bulb always used when working with a pipet?
Why are the calibration marks on laboratory beakers taken only to be an approximate guide to volume?
Precision volumetric glassware (pipets and burets) may be marked with the legend “TC” or “TD” along with a temperature. To what do each of these notations refer?
