PROPERTIES OF FLUIDS

5 PROPERTIES OF FLUIDS

VISCOSITYDENSITY & TEMPERATUREBUOYANCYCOMPRESSIONPRESSURE

VISCOSITYFluids move & flow.

VISCOSITY is how quickly fluids flow.

A fluids internal resistance or friction keeps it from flowing.

The greater the friction or rubbing between particles in any fluid, the

higher the viscosity.

FLUIDS WITH HIGH VISCOSITY DO NOT FLOW AS EASILY AS FLUIDS WITH LOW

VISCOSITY.

As the temperature of a liquid increases, its viscosity decreases.

As the temperature of a liquid decreases, its viscosity increases.

THE RAMP METHOD OF

TESTING VISCOSITY

Pour a fluid down a ramp and time how long it takes to get to

the bottom.

Pour the same amount of another fluid down the same ramp and time it to compare the viscosity

of different fluids.

Investigate the effect of temperature on viscosity by

testing the same fluid at different temperatures :

Test it at room temperature.

Warm it in hot water and test it.

Cool it in an ice bath and test it.

DENSITYDensity is the amount of matter in a

given volume.

Different substances are made of different particles.

The particles in each fluid are different from the particles in every other fluid.

The density of a fluid depends on the particles it is made of.

If the density of an object is greater than the density of a fluid, the object sinks.

If the density of an object is less than the density of a fluid, the object floats.

Some solids are less dense than some liquids. That is why wood floats on

water.

9 LAYER DENSITY

EXPERIMENT

DENSITY CONT.Density & Temperature

One substance can have different densities depending on it’s temperature.

When a substance is heated it changes state: At low temperature, it will be a solid. At high temperature, it will be q

liquid or even a gas.

A substance has greater density in its solid.

Density & Concentration

Why do you think it would be easier to float on salt water than in fresh water?

Dissolving one substance (salt) into another (water) increases the number of particles in a given volume.

Increasing the concentration of salt increases the density of a solution.

BUOYANCYAn object sinks when its density is greater than the density of the fluid it is in.

When an object is in a liquid, the force of gravity pulls it down.

The liquid exerts an opposite force, called the BUOYANT FORCE.

When the density of the object is greater than that of the liquid, the force of gravity acting on the object will be greater than the buoyant force of the liquid. The object sinks.

BUOYANCY IS THE TENDANCY OF AN OBJECT TO FLOAT WHEN PLACED IN A FLUID.

HOT AIR BALLOONSAs the air in the balloon is

heated, it becomes less dense than the surrounding air.

The buoyant force pushes the balloon up into the air.

The balloon stops rising when the buoyant force equals the force of

gravity.

(At that point the balloonist stops adding heat to the air in the

balloon.)

COMPRESSIONDEFINITION

When a force pushes on an object, the object is said to be under compression.

Objects under compression tend to deform in shape.

EXAMPLE

When you kick a soccer ball, the force of your foot compresses the ball and temporarily deforms it.

Your foot is actually compressing the fluid (air) in the ball.

COMPRESSION CONT.PROPERY OF FLUID

Gasses can be compressed much more than liquids can.

Materials in a liquid state are said to be INCOMPRESSIBLE.

EXAMPLE

Squeeze a sealed plastic bottle when it’s full of juice and then when it’s empty.

How much more can you compress it when it’s empty than when it’s full?

There is much more space between particles in the gas than between those in the liquid.

As a result, when a force is applied to the particles, much more compression takes place in the gas than in the liquid.

PRESSUREDEFINITION

Pressure is the amount of force applied to a given area.

PRESSURE = FORCE/AREA

THE DEEPER

THE WATER, THE

GREATER THE

PRESSURE

PASCAL’S LAW An enclosed fluid transmits

pressure equally in all directions.

CAN U BUILD IT?

HYDRAULIC SYSTEMDEFINITION

Uses a LIQUID as the enclosed fluid.

EXAMPLES

PNEUMATIC SYSTEMDEFINITION

Uses AIR as the enclosed fluid.

EXAMPLES

Dentist’s Drills

Jack Hammers

Paint Sprayers

Air Brakes on Trucks