Why relative density has no units

Following is the table showing different density of materials. It is to be noted that these measurements are made based on a certain temperature and pressure. Because changing the physical conditions may give a different value of density each time as the density is dependent upon that factors. As stated above the relative density is a ratio of the density of a substance with respect to the density of water.

Hence, any change in the density of either substance or water will influence the relative density ratio therefore following are the factors that affect the density of any substance and indirectly affect relative density. Increasing the volume of substance will decrease the density and vice versa is also true. We can change the volume if we heat or cool the substance.

It will accordingly change its density therefore volume is inversely proportional to density. And so the temperature increase is also inversely proportional to the density as it increases the volume if the temperature is increased.

Pressure- For instance imagine we take a glass of water from earth to space, where it vaporizes as soon as possible due to the absence of pressure. However, its density decreases since the volume has increased. As we go on increasing the pressure the density also increases proportionally as the force of attraction between the molecules strengthens and the intermolecular spaces become less hence increasing its density.

So we can say pressure is directly proportional to the density of the material. Nature of substance- As from the formula it is clear that density is a characteristic property of any material and hence the relative density is totally dependent upon the nature of substance as well as of water at a certain temperature. A bulb is completely attached to a stalk of constant cross-sectional area. The hydrometer is first floated in the reference liquid in light blue , and the displacement the level of the liquid in stalk is marked with a blue line.

The reference could be in practice water. The hydrometer is then floated in a liquid of unknown density. The change in displacement is then noted. In the example depicted, the hydrometer has dropped in the green liquid; therefore its density is lower than that of the reference liquid. It is important that the hydrometer floats in both liquids. The application of simple physical principles like the change in displacement can help determine the relative density.

Pycnometer A Pycnometer is used to determine the density of a liquid. It is usually made of glass, with a fitting ground glass stopper with a capillary tube through it, so that air bubbles may escape from the apparatus. If the flask is empty, full of water, and full of a liquid whose relative density is needed, the relative density can easily be calculated. The particle density is also calculated with a Pycnometer.

The Pycnometer is filled with a liquid of known density, in which the powder of known weight is completely insoluble. The weight of the displaced liquid is calculated, and hence the relative density of the powder.

This is widely used for tank gaging applications as a convenient means of liquid level measure and approximation and density measure. Vibrating Element Transducers: It requires a vibrating element in contact to be placed with the fluid of interest.

The resonant frequency of that particular element is measured and is related to the density of the fluid by a characterization that depends completely upon the design of the element. In new laboratories for precise measurements of relative density oscillating U-tube meters are used. Therefore, they are used in the brewing, distilling, pharmaceutical, petroleum, and other industries. Ultrasonic Transducer: Ultrasonic powerful waves are passed from a taken source, through the fluid of our interest, and into a metal detector which measures the acoustic spectroscopy of the traveling waves.

Fluid properties such as density and viscosity can be determined from the spectrum. Radiation-based Gauge: Radiation is passed from a distant source, through the fluid of our interest, and into a scintillation detector, or counter.

The source is typically taken to be the radioactive isotope cesium, with a half-life of about 30 years. An advantage of this is that the instrument is not required to be in contact with the fluid. Buoyant Force Transducer: The buoyancy force generated by a float in a uniform liquid is equal to the weight of the liquid that is displaced by the float.

Since buoyancy force is linear the measure of the buoyancy force usually yields a measure of the density of the liquid. When the object head is immersed vertically in the liquid, the float moves somewhat vertically and the position of the float controls the position of a very effective permanent magnet whose displacement is sensed usually by a concentric array of Hall-effect linear displacement sensors. The output coming signals of the sensors are mixed in a dedicated electronics machine which provides a single output voltage whose magnitude is a direct linear measure of the quantity which is to be measured.

Sample Problems Question 1: It is given that the relative density of silver is The density of water is kgm What is the density of silver in SI unit? Hence, the density of silver is kgm -3 Question 2: What is the relative density and its SI unit?

Answer: The relative density or specific density is the ratio of density of a substance with respect to the density of water at 40 C. Since the units for both the numerator and denominator in the ratio are same, they cancel each other.

Therefore, relative density has no units. The density of any substance defined as mass per unit volume. Question 3: State the difference between density and volume? Answer: Volume — States that how much space a material or substance takes up. Mass — It is a measurement of the amount of matter present in an object or substance.

Density — It is defined as how much space a material or substance takes up its volume with respect to the amount of matter in that object or material its mass. Study Materials. Why use Doubtnut? Instant Video Solutions. Request OTP. Question : Why relative density has no unit.

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