The density of an object is defined as the ratio of mass to volume. Density is used in geology, and many other physical sciences. Density also determines whether an object can float (also known as buoyancy) in water, which has a density unit of 1 gram per cubic centimeter (g/cm).3) and is the standard unit of measure for density.
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Part 1 of 2: Finding Variable Values
Step 1. Measure the mass of the fixture before starting
Especially if you are calculating the density of a liquid or gas, you need to know the mass of the container. This way, you can subtract the mass of the container from the total mass to find the mass of the object.
- Place a beaker, jar, or other container on the scale, and write the mass in grams.
- Some scales allow you to "mount" the weight. This means that after placing the container on the scale, you can press “tare”, and the scale will return to zero. Thus, the mass of the container on the scale is no longer taken into account.
Step 2. Place the object on the scale to measure mass
Whether the object does not use a container because it is solid, or uses a container because it is a liquid or gas, measure its mass with a scale. Record the mass in grams, and subtract the mass of the container used.
Step 3. Convert mass to grams if the units are different
Some scales will measure objects in units other than grams. If your scale doesn't measure in grams, we recommend converting it by multiplying the mass by the conversion value.
- 1 ounce is approximately equal to 28.35 grams. 1 pound equals 453.59 grams.
- In this case, you would multiply the object's mass by a conversion factor of 28.35 to convert ounces to grams or 453.59 to convert pounds to grams.
Step 4. Find the volume of the object in cubic centimeters
If you're lucky that the object you're measuring is a solid rectangle, simply measure the length, width, and height of the object in centimeters. You will then multiply all three to get the volume.
Step 5. Determine the volume for a solid that is not a quadrilateral
For liquids or gases you will need to use a cylindrical measuring cup or beaker to record the volume. If the object is a solid with an irregular shape, you'll need to use the right equation or submerge it in water to find its volume.
- One (1) milliliter is equal to 1 cubic centimeter. Thus, the conversion of liquids and gases can be done easily!
- There are various mathematical formulas for finding the volume of quadrilaterals, cylinders, and pyramids, and so on.
- If the object is a solid, non-porous object with no regular dimensions to measure, such as a lump of rock, you can calculate its volume by submerging it in water and measuring the volume of water remaining in the container. According to Archimedes' law, the volume of the submerged object is equal to the volume of the displaced fluid. So you simply subtract the combined volume of the liquid when it contains an object with a volume of liquid.
Part 2 of 2: Using the Density Formula
Step 1. Divide the object's mass by its volume
Using a calculator (or manually, if you want an extra challenge) divide the quantity of mass in grams by its volume in cubic centimeters. For a mass of 20 grams whose volume is 5 cubic centimeters, the density is 4 grams per cubic centimeter.
Step 2. Simplify the answer according to the number of significant digits
In the real world, the size value is usually not an integer as is usually found in problems. Thus, when dividing mass by volume, it is not uncommon for you to get long numbers with many decimal places.
- Ask the teacher to find out how many digits after the comma are needed to answer the question.
- Usually rounding to 2-3 digits after the comma is quite accurate. Thus, if the result obtained is 32, 714907, please round up to 32, 71 or 32, 715 g/cm3.
Step 3. Review the meaning of density
Usually, the density of an object is related to the density of water (1.0 g/cm3). If the density of the object is greater than 1, the object will sink. Otherwise, the object will float.
- The same relationship applies to fluids. For example, if you try to mix olive oil and water, the oil will rise to the surface because its density is less than water.
- Gravity is also another ratio that affects density. Often the density of an object is divided by the density of water (or other substance). The two units cancel each other out so you only get a number that reflects the relative mass. This number is often used in chemistry to determine the concentration of a substance in solution.
