 A fluid is a substance that has:  no definite form  Is able to flow in all directions  All liquids and gases are fluids  The body is full of fluids- gas and liquid

 Powders such as sugar, flour or sand are not fluids even though they have no form and flow  They are made of small particles of definite form *

 Fluid properties vary from one to another.  Viscosity –the ability of a liquid to flow  Honey – high viscosity  Water – low viscosity  Density  Humans use the properties of fluids for in various systems: refrigeration, hydraulic systems, air bags, anaesthetic agent*

 Pressure is the measure of the amount of force exerted on a certain area  When we push on an object we apply a force on it  If the force is high enough can move or even deform the object

 When we apply a force on a fluid, the fluid exerts a force on whatever contains it *

 Pressure (newtons/meter 2 ) = Force (newtons) Area (square meters)  The international unit for pressure is the PASCAL (Pa)  1Pa = 1N/m 2 this is a relatively small unit  kPa (1000Pa) is used to measure atmospheric pressure F P A P A

 Other units are used to measure pressure:  Millimetres of mercury (mmHg)  Atmosphere –normal atmospheric pressure at sea level  101.3kPa=760mmHg=1atm *

 The force exerted on a floor by a person standing on it consists of the person’s mass and the gravitational pull acting on it  This is what we call a persons weight = (mass x gravity)

 If the person stands on a nail the foot will be punctured How ever if the person lay down on a bed of nails the skin would not be broken Why? What is the similarity with snowshoes? *

 By changing the area the force is acting on you notice an increase in pressure Increase area decrease pressure Decrease area increase pressure *

0.5m 2 5N/m 2 Pressure varies inversely proportional to the surface area or force applied

 If 1,000N were applied to an area of 100m 2 what would the exerted force be? P=F A  If the same force (1000N) were applied to ½ the previous area( 50m 2 ) P=F A  The pressure because the area was smaller * = 1000Newtons 100 m 2 = 10N/m 2 = 1000Newtons 50 m 2 = 20N/m 2

 There is more pressure exerted under the heel of a stiletto shoe than under the Empire State Building?

 The weight of water exerts a force upon anything submersed in it  The pressure at the bottom of the barrel = the weight of the column of water directly above an area of one square cm  If the barrel were 1m high there would be 1000cm 3 of water (1kg) pushing down (1cm 3 =1g) * One cm 2 1kg

 When a person dives underwater the water column above the person pushes down on them  The deeper you dive the more pressure is exerted on your tissues  You can feel the pressure on the ear drums ( painful) - more depth and you can rupture them*

 pressure is directly proportional to the force applied Pressur e (N/m 3 Force (N)

 If 1,000N were applied to an area of 100m 2 what would the exerted force be? P=F A  If increasing the force (2000N) were applied to the same area( 100m 2 ) P=F A  Double the force = double the pressure * = 1000Newtons 100 m 2 = 10N/m 2 = 2000Newtons 100 m 2 = 20N/m 2

 A tire pumped up with air has a force exerted upon it by the air inside.  If the pressure is high enough the tire will remain firm even if pressure is applied to it  This is explained by the air molecules inside the tire having lots of energy hitting the walls  Adding more “air “ increases the number of molecules pushing outward = harder tire

 In the body, fluids exert pressure on blood vessels (arterial pressure)  The pressure difference causes fluids to move (from high pressure to low pressure)  Lungs – air moves into lung

 Compressibility is the capacity to reduce the volume by exerting a force  A gas is a fluid that can be compressed because its particles are farther apart  Air tanks for scuba divers, propane tanks

 Liquids are incompressible  Hydraulic brakes  Incompressible- impossible to decrease the volume by exerting a force  Instead of a change in volume there is a transmission of force from one particle to another inside the substance (like dominos)  The blood forced through vessels by the pumping heart

 In Chemistry, concentration is how much of a given substance there is mixed with another substance  Most often used for homogeneous solutes to describe the amount of solute in a solvent  Remember the solute is the substance that is dissolved and the solvent is the substance that does the dissolving

 The concentration of a solution is determined by dividing the mass of the solute by the volume of the solution  C = Mor Units: g/L, mg/L, g/mL V M C V C V

 To make a solution MORE concentrated you must add MORE SOLUTE. This is called a concentrate (a more concentrated version of an original solution)  To make a solution LESS concentrated you must add MORE SOLVENT. This is called a dilution (a less concentrated version of an original solution)

 Often the concentration of a solution is described using the parts per …. Notation  Parts per hundred: better known as percent (%), and means amount of a given substance in a total amount of 100 regardless of the units  Parts per thousand: (‰ or ppt) is the amount of a substance in a total amount of 1000  Parts per million: (ppm) amount of a substance in a total of 1 million

 Blood is 92% water (parts per hundred)  Legal blood alcohol content 0.8 ppt (parts per thousand)  Amount of fluorine added to treated (city) water is 1 ppm (parts per million)