Determination of the density of unknown objects
Purpose
To measure the volumes and masses of the objects using different methods and to evaluate the accuracy, precision, and effectiveness of the different methods
To determine the density of different objects made of different substances based on their measured volume and mass.
To demonstrate the proper use of absolute and percent uncertainty in measurements and calculations
Theory
The density, ρ, of an object is its mass, m, per unit volume, V, according to the equation
An object's density can be used to identify the composition of the object.
The mass can be measured using a digital scale, triple-beam balance, or a two-pan balance. The object must be dry to get an accurate measurement.
The volume can be measured by the water displaced (change in volume) when the object is completely submerged using graduated cylinders or beakers. The volume of a cylinder or a block can also be determined mathematically from its cross-sectional areas and height.
Materials clearly identify which materials were used, including sizes and uncertainties
unknown objects
graduated cylinders
beakers
ruler
calipers
triple beam balance
two-pan balance
digital scale
Procedure
Select an unknown object (ex. Unknown A) and record any qualitative and quantitative observations that can be used to determine its density and identify the nature of the object.
Repeat for two other unknowns
Results
Table 1. Mass and volume measurements using different methods and the calculated density of unknown ____
mass method |
mass, m / g |
volume method |
volume, V / cm3 |
density, ρ / g cm-3 |
digital scale |
|
displacement |
|
|
triple beam balance |
|
calculated |
|
|
two-pan balance |
|
|
|
|
Concluded Mass |
|
Concluded Volume |
|
|
Physical description of unknown ___
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