Fluids and Solids

States of Matter

There are four known states of matter: solids, liquids, gases, and plasmas.

Plasmas

systems of charged particles interacting electromagnetically— are the most common.

Solids, Liquids, Gases

Predominate the environment on Earth

Solid

has definite volume and definite shape

Solid

its molecules are held in specific locations (by electrical forces) and vibrate about equilibrium positions

Solid

At low temperatures, the vibrating motion is slight, and the atoms can be considered essentially fixed. As energy is added to the material, the amplitude of the vibrations increases.

Solid

An atom can be viewed as being bound in its equilibrium position by springs attached to neighboring atoms.

Elasticity

External forces can be applied to the solid and compress the material. When the external forces are removed, it tends to return to its original shape and size.

Crystalline Solid

the atoms have an ordered structure. For example, in the sodium chloride crystal (common table salt), sodium and chlorine atoms occupy alternate corners of a cube

Amorphous Solid

such as glass, the atoms are arranged almost randomly.

Liquid

has definite volume but no definite shape

Liquid

exists at a higher temperature than solids

Liquid

its intermolecular forces aren’t strong enough to keep the molecules in fixed positions, and they wander through the liquid in random fashion

Gas

has no definite volume nor definite shape

Gas

molecules are in constant random motion and exert only weak forces on each other

Gas

he average distance between the molecules of a gas is quite large compared with the size of the molecules.

Gas

can be easily compressed

Plasma

When a gas is heated to high temperature, many of the electrons surrounding each atom are freed from the nucleus resulting to a collection of free, electrically charged particles

Plasma

he long-range electric and magnetic forces allow the constituents of a plasma to interact with each other

Plasma

plasmas are found inside stars and in accretion disks around black holes

Specific Gravity

is a dimensionless quantity

Pressure

The force exerted on an object at any point is perpendicular to the surface of the object.

Pressure

force divided by the area

Fluid at Rest

all portions of the fluid must be in static equilibrium

Fluid at Rest

all points at the same depth must be at the same pressure

higher, lower

fluid would flow from the _____ pressure region to the _____ pressure region.

Total Pressure

is the sum of the fluid pressure and the atmospheric pressure above

Manometer, open-tube manometer

A simple device for measuring pressure is the ______. One end of a U-shaped tube containing a liquid is open to the atmosphere, and the other end is connected to a system of unknown pressure

Manometer

atmospheric pressure, ℎ is positive. If 𝑃𝑃 is less than atmospheric pressure, ℎ is negative, meaning that the right-hand column is lower than the left-hand column.

Evangelista Torricelli (1608-1647)

Inventor of the Barometer

Barometer

A long tube closed at one end is filled with mercury and then inverted into a dish of mercury.

Sphygmomanometer

is often used to measure blood pressure.

Sphygmomanometer

is calibrated to read the pressure in millimeters of mercury.

systolic, diastolic

Blood pressure readings are usually expressed as the ratio of the ____ pressure to the ____ pressure, which is 120/80 for a healthy heart.

Pascal’s Principle

A change in pressure applied to an enclosed fluid is transmitted undiminished to every point of the fluid and to the walls of the container.

Blaise Pascal (1623-1662)

French scientist who first recognized the Pascal’s Principle

hydraulic press

An important application of Pascal’s principle

Streamline/Laminar

if every particle that passes a particular point moves along exactly the same smooth path followed by previous particles passing that point.

Turbulent

above a certain velocity or under any conditions that can cause abrupt changes in velocity.

Eddy Currents

Irregular motions of the fluid

Viscosity

is used for the degree of internal friction in the fluid.

Viscosity

This internal friction is associated with the resistance between two adjacent layers of the fluid moving relative to each other.

The fluid is non-viscous

There is no internal friction force between adjacent layers.

The fluid is incompressible.

Its density is constant.

The fluid motion is steady.

The velocity, density, and pressure at each point in the fluid don’t change with time.

The fluid moves without turbulence.

Each element of the fluid has zero angular velocity about its center