 VISCOSITY  DENSITY & TEMPERATURE  BUOYANCY  COMPRESSION  PRESSURE

Fluids 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.

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.

Density 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.

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.

An 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.

As 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.)

DEFINITION  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.

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.

DEFINITION  Pressure is the amount of force applied to a given area. PRESSURE = FORCE/AREA

 An enclosed fluid transmits pressure equally in all directions.

DEFINITION  Uses a LIQUID as the enclosed fluid. EXAMPLES

DEFINITION  Uses AIR as the enclosed fluid. EXAMPLES  Dentist’s Drills  Jack Hammers  Paint Sprayers  Air Brakes on Trucks