The experiment aimed to measure the specific gravity (S.G) of some common material and determine their densities. The experiment also aimed at demonstrating the Archimedes’ principle.
Theory
The density of a material refers to the ration of mass to its volume, i.e., mass per volume and can be expressed in g/cm 3 or kg/m 3 . The specific gravity of an object refers to the ratio of its density to that of water. The formula for the calculation of density and specific gravity are shown below;
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Where
m / w
Where m =density of object
w =density of water
Archimedes’ principle states that: The apparent loss of weight of an object immersed in a fluid is equal to the weight of the fluid the object displaces. This means that there is a force that acts on the object and this force is referred to as buoyant force. This force is the one that makes the body float or reduces the apparent weight of the object that is immersed in water. The apparent weight of the object in water is equal to the weight of water displaced. The Archimedes’ principle is used to determine the specific gravity of an object that will sink in water. i.e., the density of the object is more than that of water. This is done by weighing the weight of the object in the air first and then weighing it in a while submerged in water. The weight of the water displaced by the submerged object is the apparent weight of the object in the water. The masses are then used to calculate the specific gravity of the object which is given by the formula shown below;
Equipment
Triple Beam Balance
Rubber Stopper
Wood Block
Glass Bottle
Sand, Aluminum Cylinder
Water Container
Set of Masses
Procedure
Specific Gravity of a Rubber Stopper
The color of the rubber stopper used was noted down first, and its mass in the air (M 1 ) measured and recorded in data table 1. The stopper was then immersed in water, and its mass in water measured (M 2 ) recorded too. The specific gravity of the stopper was then computed using the data obtained. The formula shown below was used.
Specific Gravity of Wood
This experiment aimed at measuring the specific gravity of a piece of wood that will float on water. To ensure that the portion of wood sinks, a sinker will be connected to it.
Procedure
The mass of the piece of wood, M 1 , was measured in air and recorded in data table 2. The combined mass of the wood in the air with the sinker under water, M 3 , was also measured and recorded in the same table. The combined mass of both the wood and the sinker submerged in water was measured and recorded. The data obtained was then used to compute the specific gravity of wood using the formula shown below.
Specific Gravity of Dry Sand
The mass of the empty bottle was measured and recorded as M B in data table 3. The bottle was then filled with sand the level of the san marked. The combined mass of the bottle and sand, M BS , was measured and recorded. The sand in the bottle was poured out into its original container and the bottle filled with water to the level marked. The combined mass of the bottle and water, M BW was measured and recorded. The data obtained was then used to calculate the specific gravity of sand using the formula shown below;
The density of an Aluminum Cylinder
The mass of the aluminum cylinder was measured in the air its mass recoded as M Air in data table 4. The mass of the aluminum cylinder was measured in water and its mass recorded as M water. The volume of the aluminum cylinder was then determined using the Archimedes’ principle.
The density of the cylinder was also determined.
Data Obtained and Data Analysis
Data Table 1: Specific Gravity of Rubber Stopper
Rubber Stopper:
Color: Grey
Calculation of S.G
The density of rubber stopper
Data Table 2: Specific Gravity of Dry Sand
Wood
M 1 =
M 3 =
M 4 =
Calculation of specific gravity
The density of wood
Data Table 3: Specific Gravity of Dry Sand
Sand
M B
M BS
M BW
Calculation of S.G of sand
Calculation of density of sand
The density of sand
Data 4. The density of an Aluminum Cylinder
Calculate Volume of aluminum foil
Discussion
The specific gravity of an object refers to the ratio of its density to that of water. The object will sink if the value of its specific gravity is greater than one and floats if the value of its specific gravity is less than one. Archimedes’ .principle states that: The apparent loss of weight of an object immersed in a fluid is equal to the weight of the fluid the object displaces. This means that there is a force that acts on the object and this force is referred to as buoyant force. This force is the one that makes the body float or reduces the apparent weight of the object that is immersed in water
The experiment involved the measuring of familiar objects or material in air and when submerged in water. As seen in the test, the mass of the objects in water was found to be less than its weight in air. The reduction in mass is as a result of buoyancy. In the first part of the experiment, the specific gravity of stopper cork and its density was calculated and found to be 1.14 and 1.14g/cm 3 respectively. In the second experiment, the specific gravity of wood, as well as its density, was found to be 1.40 and 1.40g/cm 3 respectively. In test three the specific gravity and density of dry sand were found to be 1.61 and 1.61g/cm 3 respectively. In experiment four, the volume of aluminum foil was found to be 0.62cm 3, and its density was 2.66g/cm 3 .
Conclusion
To sum up, the objective of the experiment was met. The specific gravity of some common materials, as well as their densities, were determined. The Archimedes’ principle was also well demonstrated in the experiment. However, there were some errors introduced while experimenting making the experimental values different from the theoretical ones. This includes measurement errors as well as round-off errors. To minimize or eliminate these errors, the experiment ought to be done carefully. Overall, the experiment was fruitful.
