Skip to main content. Introduction to Chemistry. Search for:. Volume and Density. Learning Objective Describe the relationship between density and volume. Key Points The volume of a substance is related to the quantity of the substance present at a defined temperature and pressure.
The volume of a substance can be measured in volumetric glassware, such as the volumetric flask and the graduated cylinder. Density indicates how much of a substance occupies a specific volume at a defined temperature and pressure.
The density of a substance can be used to define the substance. Water is unusual because when water freezes, its solid form ice is less dense than liquid water, and thus floats on top of liquid water. Show Sources Boundless vets and curates high-quality, openly licensed content from around the Internet. The tighter the particles are packed, the higher is the density of the material. Density is a bulk property, which does not depend on the size or amount of the material.
Density of a material remains constant at constant temperature. Different substances have different densities, which enables the identification of an unknown material through the evaluation of its density. The density of a liquid is important to know in many different physical applications.
The difference in densities makes some substances rise above others, in the image you can see examples of typical density values demonstrated. A - Lamp Oil 0.
Watch this video to check if you are following the correct steps for a successful density measurement with a pycnometer. Furthermore, we compare density measurement with a pycnometer vs a digital density meter.
Did you know that a temperature change of 0. The temperature influences the space necessary to fit atoms in a molecule. The vibration increases with higher temperature, moving the atoms further apart and therefore reducing the density value.
Same molecule when temperature increases moving further apart. Therefore, the higher the temperature, the higher the volume and the lower the density. If the temperature decreases, the volume becomes lower and the density becomes greater. But, the mass of the substance does not change. The only exception to this rule is liquid water, which reaches its density peak at 3. The opposite applies when water is cooled. Note: The relation among temperature, volume and density is not a linear function and it depends on the specific heat capacity, heat of vaporization and other factors of each substance.
A simple air bubble present in a liquid measured can cause a massive difference to its density and the same applies for impurities. For instance, a glass pycnometer relies on the mass for the calculation of the density value. If there is an air bubble present or a contamination e. This leads to an incorrect density value. If you are in Mexico City at 3. This means the air pressure is directly related to the altitude.
In a density measurement using a manual instrument e. Modern digital density meters feature a built in barometer pressure sensor to measure the local air pressure, which automatically sets the reference air density value. This value is important for 2 reasons:. Viscosity describes the resistance of a liquid in flowing, informally described as the "thickness" of a fluid, and in principle, it has no direct relationship with density.
Relative density is the ratio between absolute densities of two substances, where the divisor is considered the reference substance. If this substance is not specified, it is assumed to be water at 3. As per the equation, the relative density has no units. Specific gravity SG is the ratio between the density of a substance and the density of water.
If the temperature is not specified, it is assumed to be water at 3. True density is the ratio between the mass and volume of a substance at a given pressure and temperature, corresponding to its weight in a vacuum. This is the concept also used in density measurement by digital density meters.
Apparent density is a property of partitioned solids, such as powders and granules, and is often used in the mining, food and chemical industries.
By definition, apparent density is the ratio between mass and volume, but it corresponds to weight in air. To illustrate the difference between true density and apparent density, we have a pycnometer placed onto a balance.
When it is filled with a liquid, it weighs less in air than in a vacuum due to the buoyancy effect of air. Many official density tables are still based on apparent density. Digital density meters deliver results in different units and concentrations , check out their specifications. Ensuring accurate density measurement results requires taking direct action to avoid inaccuracy throughout the workflow process.
Below you will find important tips for the success of your density determination. Before you begin your measurement, it is important to understand the necessary precautions to take depending on your sample type. Regularly verify the measurement performance of your system by measuring a sample of accurately known density e. This procedure is called test, calibration or check. After completing the check or test, the measured density is compared to the known nominal value of the sample.
Additionally, it is good practice to check that the measuring cell is fully clean and dry between the analyses of different substances. For density, you also need to consider the size, or volume, of the object. A concrete cube will weigh more than a cube of air the same size because it is denser Show credits Hide from Pitsco Lighter-Than-Air Flight Density is not something that is directly measured.
Typically if you want to know the density of something you will weigh it and then measure its volume. Another tricky thing about density is that you can't add densities. If I have a rock that is made up of two minerals, one with a density of 2. This is because both the mass and the volume of the two minerals will be added, and so when they are divided to get the density the result will be between the two.
Typical densities for gasses are on the order of thousandths of grams per cubic centimeter. Liquids often have densities of about 1. To calculate the specific gravity SG of an object, you compare the object's density to the density of water:. However, specific gravity is a unitless number, and is the same in the metric system or any other measurement system.
It is very useful when comparing the density of two objects. Densities are critical for many uses.
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