Most woods exhibit a specific gravity between 0.3 and 0.8.
Specific gravity bears a close resemblance to density. Density represents the ratio of an object's or substance's mass to its volume, typically expressed in units of grams per milliliter, g/mL, or grams per cubic centimeter, g/cc. Specific gravity represents the ratio of a substance's density to the density of water at 4 degrees Celsius, which is 1.000 g/mL. Thus, specific gravity and density are numerically identical, but density bears units of g/mL or g/cc, whereas specific gravity exhibits no dimensions. The volumes of irregularly shaped solids such as rocks or pieces of wood are best measured by cubic displacement, in which the experimenter immerses the sample in a water-filled cylinder and measures the change in water level.
Instructions
1. Place the wood pellet on a balance and record its mass in units of grams. If the balance only measures in units of ounces, use an online calculator, such as the one provided in the Resources section, to convert to grams.
2. Bend the bottom quarter inch of a 6-inch piece of wire at a 90-degree angle. Hold the small portion of the bent wire flat against the surface of the wood pellet and add a very small drop of quick-dry adhesive to glue the wire to the pellet. The wire will allow you to forcibly submerge the pellet of wood in the water; the volume of the wire and glue is small enough to not adversely affect the volume measurement.
3. Fill a 100-mL graduated cylinder with about 80 mL of water. Read the volume as accurately as you can and record this number. The volume on most graduated cylinders can be read to the nearest milliliter.
4. Immerse the wood pellet into the water in the graduated cylinder, using the attached wire to submerge it. You must submerge the entire pellet to obtain an accurate reading. While holding the pellet under water, take a new volume reading from the graduated cylinder.
5. Calculate the volume of the wood pellet by subtracting the initial volume of about 80 mL from the volume with the pellet submerged. For example, for an initial volume of 81 mL and a final volume of 95 mL, the volume of the wood pellet is 95 mL - 81 mL = 14 mL.
6. Determine the density of the wood pellet by dividing the pellet's mass in grams by its volume determined by cubic displacement. For example, if the pellet weighed 10 grams and it displaced 14 mL of water, then the density is 10 g / 14 mL = 0.71 g/mL, or 0.71 g/cc. This value also represents the specific gravity when expressed without units, i.e., 0.71.
Tags: wood pellet, graduated cylinder, cubic displacement, initial volume, represents ratio, specific gravity
