Specific gravity is a comparison of a substance's density to that of water. Water's density is 1 gram per cubic centimeter (1 g/cm). The specific gravity of a substance is determined by dividing its density by that of water. Because specific gravity is determined by dividing two densities, the units cancel each other out, and the final value is given with just a number. Specific gravity can also be calculated by dividing the weight or mass of an object by the weight or apparent mass of the same object when it is submerged in water. Because each substance has a unique specific gravity, this test can determine the composition of an object.
Things You'll Need
- Spring scale
- Measuring cup
Weigh your solid by hanging it from the spring scale.
Fill the measuring cup with enough water in which to submerge your object.
Hang the object from the spring scale and lower it into the water until it is completely submerged. Record the weight of the object when in water.
Divide the weight of the dry solid by the weight of the solid when it was submerged in water. The result is the specific gravity of the solid.
Tips & Warnings
- For the purposes of this experiment, mass and weight can be used interchangeably. The acceleration due to gravity is the same for both measurements, and it will cancel out when the values are divided. In the end, your units of mass and weight will cancel out along with the acceleration due to gravity, giving you a number with no units.
- Photo Credit Jupiterimages/Comstock/Getty Images
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