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Properties of fluids , Factors affecting density and pressure

From Online Sciences - October 29, 2017

Matter can be found in nature in one of three states which are solid , liquid , gas , Solid materials ( like wood and glass ) have a definite shape and volume , while liquids and gases ( like water and air ) have no definite shape but they take the shape of their container , so , they are called fluids .

Fluids

Fluids are the materials which can flow and have indefinite shape , There are two types of fluids :

Properties of fluids

We will explain in details some of the physical properties characterizing the fluids which are density and pressure .

Density

Density is the mass of unit volume of the substance or the mass of the body divided by its volume , The density of a material is given by the relation :

= mVol

Where : m is the mass of the substance and measured in kg , Vol is the volume of the substance and measured in m3 , consequently , the density is measured in ( kg / m3 ) , When the density of iron = 7900 kg / m3 , It means that the mass of 1 m3 of iron = 7900 kg .

When mixing two or more materials then : m ( mix ) = m1 + m2 +

Vol = 1 ( Vol )1 + 1 ( Vol )2 +

Vol ( mix ) = ( Vol )1 + ( Vol )2 +

And if the mixture is diminished : Vol ( mix ) = [ ( Vol )1 + ( Vol )2 ] Vol

The factors that affect the density

Density differ from material to another because of the difference in :

Density is considered a characteristic property for the material , because it is constant for the same material and does not change as the mass or volume of the material changes at the same temperature , It changes by changing the type of material or changing the temperature because the increase in temperature changes the intermolecular spaces between atoms or molecules and consequently the density .

Applications of density

Indicating how well the battery of the car is charged by measuring the density of the electrolytic solution inside it , When the battery is discharged , the density of its electrolytic solution ( diluted sulphuric acid ) decreases because of the chemical reaction with the lead plates and the formation of lead sulphate , When the battery is recharged , the sulphate is separated from lead plates and go back to the electrolyte and the density increases again .

Diagnosis of some diseases like Anemia by measuring blood density , The normal rate of blood density ranges from 1040 kg/m3 to 1060 kg/m3 , if blood density exceeded 1060 kg/m3 , this indicates increase in the concentration of the red blood cells , Blood density preceded 1040 kg/m3, this indicates decrease in the concentration of the red blood cells which indicates Anemia .

The increase of salts concentration in urine , By measuring the urine density , The normal density of urine is 1020 kg/m3 and some diseases cause increase of salts in the urine that increase its density .

The relative density is the ratio between the density of a material to the density of water at the same temperature or it is the ratio between mass of a certain volume of a material to the mass of the same volume of water at the same temperature .

The relative density of a substance can be determined from the relations :

Relative density of a substance = Density of material at a certain temperature Density of water at the same temperature

Relative density of a substance = Mass of a certain volume of a material at a certain temperature Mass of the same volume of water at the same temperature

The relative density is dimensionless because it is a ratio between two similar quantities , when the relative density of gasoline is 0.9 , It means that the ratio between the density of gasoline to that of water at the same temperature = 0.9 .

The density of a material can be determined by knowing its relative density using the following relation :

material =relaive water = relaive 1000

( Where : water = 1000 kg / m3 )

Pressure

When a force ( F ) acts on a surface of area ( A ) , pressure ( P ) is produced on this area , The pressure at a point is the average force acting perpendicularly on the unit area surrounding this point .

Force perpendicular to the surface , so , P = F / A , mg / A

Factors affecting the pressure at a point :

Applications on the pressure

Elephant foot pressure or mans ?

Pressure at a point inside a liquid

Deduction of the pressure value at a point inside a liquid

Fg = mg

P = gh

Factors affecting the pressure at a point inside the liquid :

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