Properties of Fluids Unit 5 Hydraulic and Pneumatic Systems Lesson 1

Properties of Fluids The science and technology of the mechanical properties of liquids is called hydraulics. Similarly, the science and technology of air and other gases is called pneumatics.

A Fluid is a substance that flows and takes the shape of its container; liquids and gases are both fluids. If the fluids are at rest, the study of them is called fluid Statics.

The study of hydraulics and pneumatics includes the study of fluids that are not enclosed, such as lakes and air in the atmosphere as well as pressurized systems that are enclosed. A hydraulic system is a mechanical system that operates using a liquid under pressure A pneumatic system operates using a gas under pressure.

Density and Compressibility 1. All Matter is made up of extremely tiny particles 2. Each Pure substance has its own kind of particles, different from the particles of other pure substances 3. Particles are always moving. Particles at a higher temperature are generally moving faster, on average than particles at a lower temperature. 4. Particles attract each other

There are three states of matter. Gas, Liquid, and Solid. All three of these states are physical states of matter.

There is also a forth, it is called a plasma which has charged particles that can conduct electricity and are influenced by magnetic fields. It is similar to a gas in its properties

Physical Properties of Solids, Liquids and Gases PhaseStructure Movement of Particles Shape of Sample Density Compressibil ity Solid - Particles closely packed - Particles in fixed positions - Vibration -Definite shape -Volume of its own -Usually more dense than liquid or gas -Cannot be compressed significantly Liquid -Particles Closely packed - Particles not fixed in position - Vibration - Rotation - Translation (slower) - Takes shape of container - Volume of its own - Usually less dense than solid - Cannot be compressed significantly Gas- Particles widely spaced - Particles not fixed in position - Vibration - Rotation, - Translation (fast) - Occupies entire volume of container - Much less dense than solid or liquid - Can be easily compressed

Two properties of matter that are particularly important to the study of fluids are density and compressibility. Density – The mass per unit volume of a substance; it is a scalar quantity with SI units of kg/m 3

Density Density can be found using the formula VolumeMass Where D is the density, m is the mass and V is the volume

Example1 A quantity of helium gas at 0° C with a volume of 4.00 m 3 has a mass of kg. (in this case the helium gas is at atmospheric pressure.) Determine the density of this sample of helium gas. V= 4.00 m 3 m = kg D = ?

D = kg/m 3 The density of the helium gas sample is kg/m 3

Density is a characteristic property of a substance, any sample of a pure substance has the same density. It does not matter how large or where the sample was taken from. The density of a substance can also be used to identify an unknown sample.

NOTE: The temperatures of all samples must be stated when comparing densities; the pressure of the gas should also be stated as density increases in gasses as pressure increases.

Compressibility – the ability of the particles of a substance to be pressed closer together. Particles in gasses are spread out, this makes them highly compressible. Liquids on the other hand are only slightly compressible and solids are even less compressible. The property of compressibility influences the choice between hydraulic and pneumatic systems.

Questions For each of the following substances, calculate the density in a convenient unit. See the extra table given to you to determine the substance. ◦ A volume of 0.50 m 3 of a substance has a mass of 6.3 x 10 2 kg ◦ A volume of 5.00 L of a substance has a mass of 3.95 x 10 3 g ◦ A volume of 75 mL of a substance has a mass of 77 g A rectangular solid brass plate is 8.0 cm long, 6.0 cm wide, and 1.5 cm thick. ◦ Calculate the volume of the plates in cubic centimetres. ◦ Calculate the plates mass in grams and kilograms.

Water can be observed as a ice, water, and vapour. Which of these states can be called a fluid? What is the difference between hydraulics and a hydraulic system? A block of metal is 50.0 cm long, 20.0 cm wide, and 15.0 high. Its mass is 128 kg. ◦ Write the block’s dimensions in metres ◦ Calculate the volume of the block in cubic metres ◦ Calculate the blocks density ◦ What is the identity of the metal ?