Density is a basic property of matter defined as the mass of an object per unit volume. If two objects have the same volume, but different densities, the object with higher density will weigh more than the object that has the same appearance but lower density. Since no two metals have the same density, knowing the density of an object can be a valuable method of determining the composition of a sample of an unknown material.
Steps
Method 1 of 2: Measure Density Directly
Step 1. Determine the mass of the object
Mass is the amount of matter in an object and its unit is the gram. This is measured by weighing the object directly.
- Place the object on a precision scale and record the mass in your notebook.
- Alternatively, you can measure the mass using a pan scale. Place the object on one side and place weights of a known mass on the other side until both sides are balanced. The total mass of the weights on the balance is equal to the mass of the object.
- Make sure the object is dry so that the absorbed water does not affect the accuracy of the weighing.
Step 2. Calculate the volume of the object by direct measurement
If the object has a regular and uniform shape, such as a cylinder or rectangular prism, you can measure its dimensions with a ruler and calculate the volume with a simple equation.
- Measure the length and radius if it is a cylinder; or the length, width and depth if it is a rectangle.
- Write down the dimensions in millimeters or centimeters.
- Find the volume using the formula for the shape of the object. For example, the volume of a cylinder is the length times pi times the radius squared, while the volume of a rectangle is the product of the length, width, and depth.
- The units of volume are cubic centimeters.
Step 3. Find the volume of the object using displacement
Measuring the dimensions of objects that have an irregular shape can be difficult and can lead to inaccurate density measurements and calculations. By measuring the amount of water displaced by an object, you can easily determine its volume without complex formulas.
- Fill a graduated cylinder with enough water to completely submerge the object, but without spilling it.
- Write down the water level in the glass.
- Carefully place the object inside the glass, making sure it is fully submerged.
- Write down the new water level in the glass.
- Subtract the new water level from the initial water level. This is the volume of the object in cubic centimeters. Liquids are generally measured in millimeters, however one millimeter is equal to one cubic centimeter.
Step 4. Find the density
Density is defined as mass divided by volume. To finish the density measurement, divide the mass you measured by the volume you calculated. The result is the density of the metal measured in g / cubic cm.
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Density = Mass / Volume { displaystyle Density = Mass / Volume}
Método 2 de 2: Estimar la densidad con el principio de Arquímedes
Step 1. Fill containers with liquids of a known density
Choose liquids of high and low densities. The estimate will be more accurate if you have a series of liquids of varying densities.
Put the object inside the different liquids to see if it sinks or floats
Step 2. Test the object in the liquids
An object completely immersed in a fluid of a similar density will float within it. If it is less dense, it will float, but if it is more dense, it will sink.
- Drop the object into a fluid of a known density.
- If it sinks, try putting it in a different fluid that is denser. If it floats, put it in a fluid that is less dense.
Step 3. Estimate the density of the object
Archimedes' principle states that an object immersed in a fluid will produce a buoyant force equal to the weight of the displaced fluid.