Density can be defined as the quantity of a substance per unit volume. Usually, it is represented using the letter ρ or D; ‘ρ’ is pronounced as ‘rho’. The density formula is ρ = m/v, where ‘v’ is the volume of the given substance and ‘m’ is its mass. From the formula, it is obvious that density directly increases with the substance’s mass and is indirectly proportional to the substance’s volume.
The density of a substance changes with pressure and temperature. This fluctuation is usually less for liquid and solid substances but much larger for gases. Increasing the pressure on a body reduces the volume of the body, and thus density increases. Rising the temperature of the material (with some exceptions) reduces its density by expanding its volume. In most substances, heating a fluid’s bottom generates convection of the heat from its bottom to the top. It is due to the reduction in the given liquid’s density, which forces it to increase relative to a denser unheated substance. The reciprocal of a substance’s density is sometimes called specific gravity, a quantity used in thermodynamics. Now let’s dive into the fundamentals of relative density.
What is Relative Density
Relative density is the ratio of a material’s density to the density of the reference material. In some scenarios, It is also referred to as specific gravity. A liquid’s relative density is nearly always calculated relative to water at its highest density point (at 39.2 °F or 4 °C). In the case of gases, the reference material is air at 20 °C or 68 °F temperature.
If a material’s relative density is less than ‘one’, then the material is less dense than the given reference material. If it is larger than ‘one’, then it is much denser than the reference substance. When the value is exactly equal to ‘one’, then both the densities are equal. Equal volumes of the given two materials have exactly the same mass. If the reference substance is water, then a material with a relative density much less than ‘one’ will float in water. An ice cube possesses 0.91 relative density and always floats on water. A material which has a relative density above ‘one’ will sink in water.
The video explains the basic properties of water
Uses of Relative Density
Relative density helps to quantify a material’s buoyancy in a gas or fluid. In other words, it is used to determine an unknown material’s density from another material’s known density. Mineralogists and geologists often use it to determine the mineral composition of a rock or other materials. Geologists make use of it as a help in distinguishing gemstones. It can also be applied to analyse the purity of materials.
Relative Density and Archimedes’ Principle
Archimedes’ principle defines that if an object is immersed full or partially inside a fluid, the object will encounter a force that is equal to the displaced fluid’s weight. This principle is employed to find the purity of metals, quality of liquid, design ships etc. Relative density also helps to determine a floating body’s proportion that will be immersed in a fluid. If the object is half dense as the fluid, then half of the object will be immersed, displacing in action a fluid’s volume whose weight is the same as the body’s entire weight.
Important Relative Density Questions with Answers
1) What is meant by density?
Density can be defined as the quantity of a substance per unit volume. Usually, it is represented using the letter ρ, or D. ‘ρ’ is pronounced as ‘rho’. The density formula is ρ = m/v, where ‘v’ is the volume of the given substance and ‘m’ is its mass. From the formula, it is obvious that density directly increases with the substance’s mass and is indirectly proportional to the substance’s volume.
2) What is the connection of density with temperature and pressure?
The density of a substance changes with pressure and temperature. This fluctuation is usually less for liquid and solid substances but much larger for gases. Increasing the pressure on a body reduces the volume of the body, and thus density increases. Rising the temperature of the material ( with some exceptions) reduces its density by expanding its volume. In most substances, heating a fluid’s bottom generates convection of the heat from its bottom to the top. It is due to the reduction in the given liquid’s density, which forces it to increase relative to a denser unheated substance.
3) What is meant by relative density?
Relative density is the ratio of a material’s density to the density of the reference material. In some scenarios, It is also referred to as specific gravity. A liquid’s relative density is nearly always calculated relative to water at its highest density point (at 39.2 °F or 4 °C). In the case of gases, the reference material is air at 20 °C or 68 °F temperature.
4) Explain the analysis of relative density.
If a material’s relative density is less than ‘one’, then the material is less dense than the given reference material. If it is larger than ‘one’, then it is much denser than the reference substance. When the value is exactly equal to ‘one’, then both the densities are equal. Equal volumes of the given two materials have exactly the same mass. If the reference substance is water, then a material with a relative density much less than ‘one’ will float in water.
5) Give an example of the application of relative density.
An ice cube possesses 0.91 relative density and always floats on water. A material which has a relative density above ‘one’ will sink in water.
6) What is another name for relative density?
In some cases, relative density is called specific gravity.
7) What are the main uses of relative density?
Relative density helps to quantify a material’s buoyancy in a gas or fluid. In other words, it is used to determine an unknown material’s density from another material’s known density. Mineralogists and geologists often use it to determine the mineral composition of a rock or other materials. Geologists make use of it as a help in distinguishing gemstones. It can also be applied to analyse the purity of materials.
8) Explain Archimedes’ principle and relative density.
Archimedes’ principle defines that if an object is immersed full or partially inside a fluid, the object will encounter a force that is equal to the displaced fluid’s weight. This principle is employed to find the purity of metals, quality of liquid, design ships etc. Relative density also helps to determine a floating body’s proportion that will be immersed in a fluid. If the object is half dense as the fluid, then half of the object will be immersed, displacing in action a fluid’s volume whose weight is the same as the body’s entire weight.
9) What is the symbol used to represent density?
Density is represented using the letter ρ, or D. ‘ρ’ is pronounced as ‘rho’.
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Practice Questions
1) What is the difference between density and relative density?
2) What is the formula for density?
3) Which substance is used as a reference for determining the relative density of a liquid?
4) Which substance is used as a reference for determining the relative density of a gas?
5) Explain the special properties of water at 4°C.
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