Required Materials
A balance with at worst 0.1 g precision. This can be a laboratory or kitchen balance.
Containers to be used for weighing samples. You can use small bowls or plates, measuring cups, ¼ sheet of paper (for solid object), etc.
Measuring cup or beaker for measuring and pouring the granular solid and water.
A small solid object small enough to fit into a container placed on the balance.
At least 50 g of a granular solid. This can be any type of granular solid; for example, sand, salt, sugar, baking soda, etc.
1 quart of water.
Safety Precautions
If you choose objects that are breakable, be careful not to drop them.
Be careful with the solid object, granular solid, and water; keep them away from your eyes.
Note: all of the materials used should be safe to use in a typical kitchen.
Procedure
In quantitative analytical work always record the balance readings directly into your data and observations.
Place the balance on a flat, hard, level surface. Turn on the balance and push the tare or zero button.
A. Determining 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. Determining 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. Determining 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?
Results and Observations
A. Determining the mass of the solid object
Description of the object:
Description of Container A:
Trial 1 Trial 2 Trial 3
Mass of Container A
Mass of Container A and the Solid Object
Mass of the Solid Object
Average Mass of the Solid Object
Mass of the Solid Object (w/o difference method)
B. Determining the Mass of a Granular Solid
Description of the Granular Solid:
Description of Container B:
Trial 1 Trial 2 Trial 3
Mass of Container B
Mass of Container B and the Granular Solid
Mass of the Granular Solid
Average Mass of the Granular Solid
C. Determining the Mass of a Liquid
Trial 1 Trial 2 Trial 3
Mass of Container C
Mass of Container C and the Water
Mass of the Water
Average Mass of the Water
* Upload one picture for each part of the lab (A, B, and C) with your report sheet
Post-Laboratory Questions
After determining the mass of the Solid Object using the difference method, you tared the balance with the Container A on it, then placed the Solid Object into Container A to determine its mass. Did the resulting mass determination agree with that determined using the difference method? Explain why your results do or do not make sense.
Why is it important always to use the same balance during the course of an experiment? Explain using examples from your own data.
